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Evaluation and Retrofitting of Building Foundations

1. Survey on the Integrity of Building Foundations 1.1 Introduction 1.2 Survey on the ground surface 1.3 Survey on the underground foundations 1.4 Survey on Bearing Capacity 1.5 Evaluation of degree of damage 2. Restoration and reinforcement of building foundations 2.1 Outline 2.2 Repair, reinforce, settlement restoration 2.3 Restoring the settled, detached houses Annexes Annex 1 – Integrity Investigation Techniques Annex 2 – The Techniques of Restoration, Reinforcement and Settlement Restoration Annex 3 – Countermeasure Techniques Against Differential Sedimentation

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1. Survey on the integrity of foundations 1.1 Introduction

Generally, in the case where any of such damages as differential sedimentation, inclination, cracks, and defects has been caused to foundations by an earthquake or consolidation settlement, a survey on the integrity of foundations is required. Great attentions should be paid to the sites, which may involve the risk of liquefaction or a settlement disaster, even if no differential settlement has been actually occurred. Nevertheless, for existing buildings, the actually-occurring phenomena such as differential settlement and inclination of the buildings and cracks in the foundation members tend to attract greater attention than the results of evaluations based on design calculation. In contrast, recently, precast piles and improved soil materials have been increasingly used in housing renewal and therefore, the supporting performance of precast piles needs to be confirmed.

The evaluation items of foundation integrity may be largely classified as shown below: 1) Location of a foundation 2) Dimensions and geometry of the foundation 3) Quality of the foundation (strength/rigidity) 4) Bearing performance of the foundation

Data on the location of the foundation in 1) and the dimensions and geometry of the foundation in 2) are useful at the stage of survey if design documents and construction execution reports are available. In many cases, no detailed record has been stored. The design documents used for building construction authorization may be kept by the owner but the construction execution reports have not kept anywhere in many cases except for special cases. In the survey on the earthquake damages, the foundation might have to be digging out for visual check. On the other hand, in some cases, the dimensions and geometries of foundation slabs and footings are different from those described in the design drawing in some cases and thereby, it is very important that the detail of the foundation referring not only to the design document but also to the construction execution report. The length of the pile may be roughly estimated by the IT test (PI test). For a bearing pile, its length may be different from the measured length depending on the depth of the bearing stratum and therefore, it is necessary to confirm it referring to the construction execution report.

To determine the quality of the foundation, the strength test and the neutralization test are

conducted using coarse samples for concrete, and the strength test as well as the check test for any corrosion are require for reinforcement. With an exception of the case where:

1) reuse of the existing foundation is required, 2) differential settlement and inclination has occurred, or 3) cracks or defects is found in the rising part of the foundation on the surface of the ground which may be visually checked,

almost no survey on the quality of the foundation is conducted (Photo 1.1.1). The bearing performance of the foundation is generally evaluated based on the differential settlement or inclination if any. Thereby, the integrity is not considered in reusing the existing piles with the exception when the bearing force needs to be verify by the loading test.

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Photo 1.1.1 Method of conducting a survey on concrete integrity (general survey on concrete structures) 1) core recovery 2) core strength test 3) reinforced concrete gauge 4) reinforced concrete gauge 5) carbonation test (peeled off) 6) carbonation test (drilled out) 7) carbonation test (sampled core) 8) impact strength measurement Supplied by: Hitoshi HAMAZAKI (Building Research Institute) (excluding 2) and 4))

1 2

3 4

5 6

7 8

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In conducting the survey on the integrity of the existing foundation, the sampling test or the nondestructive test is compelling to be carried out in many cases because it is difficult to conduct in-depth survey on the entire foundation under the ground, which cannot be visually checked. In making an attempt to improve the reliability of this type of test, analysis using execution management data is useful and it is important to get deep inside into variations and differences in executed construction based on the result of execution management. At the present time, however, almost no construction execution report is prepared for evaluating variations and differences in executed construction and therefore, there is an urgent need to develop any technique for solving this problem.

Building Research Institute is making efforts in developing a quality control system (3-DQC) for visualizing information on construction execution in cooperation with Koda/Satoh’s Laboratory. This system provides correlated information on parameters such as excavation resistance per unit depth and material input relative to any of vertical and horizontal cross sections in the area under construction for easy identification (for example, M. Tamura, H. Sato et al, A 3-Dimensional Quality Control System in Foundation Construction, ISOPE, Toulon, France, 2004). Fig. 1.1.1 shows an example of the results from the management process of the deep mixing method of soil stabilization. Any of methods, which can automatically acquire and manage data on construction execution, may give similar views to the view shown above including the deep mixing method of soil stabilization and the penetration method of rotating piles using stirring blades. This management method provides such a function that a group of piles are managed together rather than individuals, allowing the constructor to grasp any variations in the geological stratum and any differences in construction during or immediately after construction and therefore, is expected to be useful in evaluating the integrity of the existing foundations.

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Besides, it is also effective to use any method for easy survey on the integrity of the

foundations when new piles are constructed. Photo 1.1.2 shows a marker for measuring any differential settlement installed on the rising part of the house foundation at the completion of construction. It is strongly recommended that this type of marker to be used to verify the horizontal plane prior to construction.

10 11 12 13 14 15 16 17 18

0.2

0.4 190.0

0.6 160.0 160.0 175.0 165.0 170.0 170.0 160.0 175.0 190.0

0.8 155.0 165.0 160.0 150.0 175.0 170.0 160.0 180.0 185.0

1.0 160.0 155.0 150.0 160.0 170.0 170.0 160.0 175.0 180.0

1.2 165.0 160.0 155.0 170.0 175.0 165.0 160.0 165.0 180.0

1.4 155.0 160.0 165.0 165.0 170.0 170.0 160.0 165.0 175.0

1.6 145.0 145.0 150.0 145.0 155.0 165.0 165.0 150.0 175.0

1.8 135.0 135.0 130.0 140.0 145.0 140.0 160.0 150.0 155.0

2.0 115.0 125.0 125.0 125.0 125.0 130.0 155.0 160.0 160.0

2.2 105.0 110.0 115.0 110.0 135.0 120.0 150.0 160.0 155.0

2.4 110.0 95.0 120.0 115.0 130.0 120.0 145.0 155.0 160.0

2.6 120.0 105.0 120.0 115.0 155.0 145.0 155.0 150.0 160.0

2.8 120.0 115.0 135.0 130.0 165.0 145.0 150.0 155.0 160.0

3.0 115.0 140.0 130.0 145.0 180.0 155.0 145.0 150.0 155.0

3.2 135.0 140.0 145.0 155.0 170.0 155.0 150.0 160.0 155.0

3.4 145.0 150.0 155.0 155.0 175.0 160.0 155.0 155.0 165.0

3.6 150.0 150.0 155.0 160.0 175.0 160.0 150.0 160.0 155.0

3.8 160.0 160.0 165.0 150.0 170.0 165.0 150.0 150.0 165.0

4.0 155.0 150.0 155.0 160.0 160.0 155.0 150.0 160.0 155.0

4.2 150.0 165.0 155.0 160.0 165.0 150.0 145.0 160.0 160.0

4.4 160.0 160.0 155.0 155.0 160.0 170.0 155.0 155.0 160.0

4.6 150.0 150.0 155.0 155.0 160.0 150.0 155.0 165.0 165.0

4.8 150.0 160.0 155.0 160.0 175.0 155.0 155.0 150.0 155.0

5.0 250.0 233.3 250.0 248.3 340.0 396.4 245.0 261.7 261.7

Column Number

Dep

th (m

)

Fig. 11 Number of mixing per 1 meter advance at X-3

10 11 12 13 14 15 16 17 18

0.2

0.4 190.0

0.6 160.0 160.0 175.0 165.0 170.0 170.0 160.0 175.0 190.0

0.8 155.0 165.0 160.0 150.0 175.0 170.0 160.0 180.0 185.0

1.0 160.0 155.0 150.0 160.0 170.0 170.0 160.0 175.0 180.0

1.2 165.0 160.0 155.0 170.0 175.0 165.0 160.0 165.0 180.0

1.4 155.0 160.0 165.0 165.0 170.0 170.0 160.0 165.0 175.0

1.6 145.0 145.0 150.0 145.0 155.0 165.0 165.0 150.0 175.0

1.8 135.0 135.0 130.0 140.0 145.0 140.0 160.0 150.0 155.0

2.0 115.0 125.0 125.0 125.0 125.0 130.0 155.0 160.0 160.0

2.2 105.0 110.0 115.0 110.0 135.0 120.0 150.0 160.0 155.0

2.4 110.0 95.0 120.0 115.0 130.0 120.0 145.0 155.0 160.0

2.6 120.0 105.0 120.0 115.0 155.0 145.0 155.0 150.0 160.0

2.8 120.0 115.0 135.0 130.0 165.0 145.0 150.0 155.0 160.0

3.0 115.0 140.0 130.0 145.0 180.0 155.0 145.0 150.0 155.0

3.2 135.0 140.0 145.0 155.0 170.0 155.0 150.0 160.0 155.0

3.4 145.0 150.0 155.0 155.0 175.0 160.0 155.0 155.0 165.0

3.6 150.0 150.0 155.0 160.0 175.0 160.0 150.0 160.0 155.0

3.8 160.0 160.0 165.0 150.0 170.0 165.0 150.0 150.0 165.0

4.0 155.0 150.0 155.0 160.0 160.0 155.0 150.0 160.0 155.0

4.2 150.0 165.0 155.0 160.0 165.0 150.0 145.0 160.0 160.0

4.4 160.0 160.0 155.0 155.0 160.0 170.0 155.0 155.0 160.0

4.6 150.0 150.0 155.0 155.0 160.0 150.0 155.0 165.0 165.0

4.8 150.0 160.0 155.0 160.0 175.0 155.0 155.0 150.0 155.0

5.0 250.0 233.3 250.0 248.3 340.0 396.4 245.0 261.7 261.7

Column Number

Dep

th (m

)

Fig. 11 Number of mixing per 1 meter advance at X-3

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

0.2 1.6 1.8 1.3 1.2 1.5 2.3 1.1 1.8 1.6 2.2 2.2 7.8 2.2 1.3 2.1 2.3 1.4 2.8 1.9 1.4 1.2 2.2 1.6 1.5 8.2 2.2

0.4 7.1 7.4 3.5 3.9 7.1 8.9 3.7 7.1 7.0 4.3 3.6 9.2 7.4 3.7 8.6 7.1 3.5 7.3 6.9 1.9 4.3 8.9 3.4 1.8 8.2 3.7

0.6 9.3 9.3 8.9 8.7 9.0 9.4 8.6 9.3 9.5 9.0 6.6 9.2 8.7 7.2 9.0 8.9 6.9 9.3 9.0 3.9 9.5 9.1 9.3 3.9 8.7 6.7

0.8 9.5 9.4 9.3 8.7 9.3 8.9 9.2 9.2 9.1 8.8 8.7 9.0 8.8 9.1 9.2 8.7 9.2 9.4 8.8 9.1 9.2 9.1 9.3 9.0 9.6 8.8

1.0 9.6 9.2 9.1 8.9 9.2 8.6 9.1 9.2 8.9 8.6 8.8 8.8 8.7 9.3 8.9 8.8 7.4 9.0 7.2 8.8 9.1 9.1 9.5 9.3 9.7 9.3

1.2 9.5 9.1 9.1 9.3 8.9 8.9 7.4 9.8 9.0 8.7 8.3 7.5 8.5 9.2 8.5 8.4 3.9 9.0 4.1 8.9 9.4 8.7 10.0 10.4 9.5 8.9

1.4 9.4 8.9 8.5 9.1 8.9 8.8 3.9 9.4 9.1 8.5 8.3 3.8 8.4 9.0 8.7 6.9 3.9 9.3 2.6 9.1 9.2 8.9 8.9 9.5 8.9 7.2

1.6 9.4 9.1 8.9 9.0 8.6 8.4 2.3 8.9 9.0 8.6 7.1 4.0 8.0 9.2 8.6 4.2 8.3 9.2 4.2 8.9 9.0 8.9 8.4 8.7 8.7 2.6

1.8 9.3 9.3 9.0 8.8 8.4 8.7 3.9 8.9 9.0 8.5 8.6 7.2 8.4 9.2 8.4 7.2 8.8 9.2 7.3 8.8 9.1 8.9 8.6 8.9 8.4 4.4

2.0 9.4 9.1 9.0 9.4 8.6 9.1 8.5 8.9 9.2 9.1 9.0 8.9 8.7 9.1 9.0 8.6 9.4 9.2 9.0 8.9 9.2 9.0 9.2 9.2 9.3 9.0

2.2 9.2 9.0 9.2 9.5 9.0 9.4 9.0 8.9 9.1 9.0 9.2 8.8 8.8 9.5 9.0 8.7 7.6 9.4 9.0 9.0 9.3 9.0 7.6 9.2 8.7 8.9

2.4 9.1 9.3 9.4 9.2 8.9 9.1 9.0 9.2 9.1 9.4 9.2 8.8 9.1 9.2 9.1 9.0 9.1 9.1 9.2 9.2 9.4 8.9 9.1 9.2 8.8 9.1

2.6 9.5 9.1 9.4 9.8 9.3 9.1 9.1 9.2 8.9 10.3 8.8 9.1 8.9 9.3 8.9 8.9 9.7 8.8 9.6 9.3 9.4 9.0 10.2 9.1 9.6 8.9

2.8 9.6 9.4 9.6 9.7 9.1 9.1 8.9 9.3 5.8 9.1 8.8 9.0 8.7 9.3 9.0 8.6 9.3 9.2 9.2 9.4 9.1 8.8 10.8 8.9 10.5 9.3

3.0 10.0 8.8 9.7 9.5 9.3 9.1 8.7 9.5 9.1 8.7 9.1 9.0 9.0 9.2 9.1 9.0 9.3 9.1 9.3 9.2 9.2 9.2 8.8 9.1 9.2 9.1

3.2 9.8 8.9 9.5 9.6 9.0 9.1 9.0 9.6 8.9 9.4 8.9 9.1 9.3 9.1 8.9 9.3 9.6 9.1 10.0 8.6 9.9 10.0 9.7 9.4 8.8 8.6

3.4 10.7 9.5 9.0 9.6 8.9 8.8 9.1 9.9 9.2 10.4 9.2 8.9 9.5 9.3 10.4 9.1 9.8 9.8 9.6 10.1 11.5 12.2 9.7 9.7 8.6 8.5

3.6 11.6 11.8 9.5 9.3 9.5 9.0 10.0 9.8 9.4 9.5 6.8 9.1 9.0 10.9 7.2 9.3 11.6 10.8 11.4 11.1 13.9 11.0 10.0 10.1 10.2

3.8 11.2 14.6 10.4 11.8 12.6 11.7 10.3 10.5 12.8 9.2 9.0 8.8 10.3 16.6 10.1 9.8 13.4 8.6 14.2 13.8

4.0 18.5 13.3 14.1 17.7 9.9 8.6 9.1 9.6 8.4 9.5 11.4 12.4 9.2

4.2 10.9 10.9 8.4 9.1 9.8 10.5 14.1 9.3

4.4 11.8 10.1 8.9 8.4 12.0 8.4

4.5 14.0 10.8 10.6 10.1

Column Number

Depth

(m)

Fig. 1.1.1 Example of the result of quality control for visualizing any change or variation in construction (3-DQC) (Example of correspondence between the number of rotations/the state of

running and column numbers/depth torque or in the deep mixing method of soil stabilization)

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Alternatively, to sense damages in addition to differential settlement and inclination,

sensors and inspection windows may be prepared on the foundation members such as piles prior to construction. Several methods have been proposed for attaching optical fibers or carbon fibers to the pile bodies or winding them around the piles. Photo 1.1.3 is an example of PHC piles with optical fibers buried inside, method still under development. It has been verified that the optical fibers can endure centrifugal fabrication. Fig. 1.1.2 shows a schematic drawing explaining this type of damage detection technique.

Difficulties may arise not only in the evaluation of where responsibility for repair of

damages lies or how severe of damages, but also in the determination of whether the repair work is required and in the repair work itself. Accordingly, if the damage detection system for the structures such as foundations as shown in the figure is required, this type of piles are expected to be put into practical use in future considering their importance/use and user’s expectation to reusability. Unfortunately, such piles are not commonly used. In the case where any of construction methods, where piles and other members are built on site, such as the cast in-place concrete pile methods the procedure may be the following: two or more inspection windows

定点マーカー

Photo 1.1.2 Marker put the periphery of the house foundation for settlement monitoring

Photo 1.1.3 Example of PHC piles damage device survey method using optical fibers. Any cracks are checked by the bending test on piles with optical fibers attached

Fig. 1.1.2 Example of pile foundation damage detection system

Marker

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(steel pipes or PVC pipes) are buried inside the pile bodies along reinforced concrete baskets and then a transmitter/receiver is inserted into each of the inspection windows as in the case of non-destructive integrity surveys (see Annex 1) such as borehole sonar detection and ultrasound or gamma logging to evaluate the integrity of the pile bodies between two windows at each of predetermined depths. It is assumed that the actual state of the foundation will be confirmed at the completion of construction through this survey. The result of the confirmation may allow for easy recognition of the integrity and deterioration of the existing foundation when it is reused later. 1.2 Survey on the ground surface

In the survey on the ground surface, 1) any differential settlement/inclination and 2) crack/defect in the foundation are checked. To check for any differential settlement and inclination, a level tube is used in many cases. Recently, an auto level may be used to check to see if any differential settlement and inclination have occurred in a short period of time. In an example of settlement restoration done in a foreign country introduced in Section 2.4, the leveling tube or manometer is used to manage and display the presence of differential settlement using contours. It is required that on the ground surface, not only the foundations but also the floors and columns to be checked for any inclination (Photo 1.2.1).

Photo 1.2.1 Example of method for measuring foundation integrity (simple measurement, for example, visual check or non-destructive test) Inclination measurement using a auto level or leveling tube, crack width measurement using a crack gauge, repulsive strength measurement, etc.

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In most of standard buildings, the rising element of the foundation can not be visually checked. On the other hand, for small-sized houses such as detached houses, cracks or flaws of the external portion of the foundation are used as an indicator of possible defects. Accordingly, it is important that the survey on the element of the foundation, which may be visually checked, to be conducted. To check to see if defects have occurred for confirmation of the integrity of the concrete foundations on the ground surface, simple instruments such as an insert clearance gauge, as well as magnifying mirrors for check the widths of cracks, repulsive strength measuring devices, and reinforced concrete exploration devices may be used.

In recent years, any soft coating material has been applied to the external elements of the foundations in some cases and therefore, it is required that the widths of cracks and other flaws to be measured fully considering the kind and properties of a finishing material. 1.3 Survey on the underground foundations

One of the direct foundations structure representative damage is inclination of rigid members witch is usually evaluated to be minor, even if the building differentially settles. This type of damage is not representative for pile foundations. For direct type, the underground part of the foundation is buried near the surface and can the ground can be excavated to check the integrity of them visually.

It may be difficult to visually check the foundation integrity for the old buildings because the survey require dig-out the piles and loading test. Recently for direct and piles foundations much frequently are used soil improvements technique. Accordingly it is more important than ever to evaluate the integrity of the improved soil if differential settlement or any other damage occurs.

During the Miyagi Prefecture Earthquake (1978) and Southern Hyougo Earthquake (1995) many piles have been damaged. The damages were found not only at the heads but also in the middle portions of the piles. To estimate or visually checked for any damage in the middle portions and heads of piles, surveys and tests are conducted from the heads of the piles or through the hollow portions or bore holes, which have been opened in the piles.

The terms of survey are classified largely into 1) those on the foundations directly beneath the building and 2) those on the underground foundations. For the direct type, the survey on the directly beneath the building is generally conducted, while any other inspection is required depending on the pile type if soil improvement or reinforcement such as the deep mixing method of soil stabilization have been employed to protect the piles.

Table 1.3.1 summarizes the individual surveys. In conducting the survey, it is always required to allow for determining whether the damages to the foundation have been caused due to insufficient bearing capacity of the foundation or due to the defect in the pile, as well as checking to see if the precast piles may be reused for selecting appropriate restoration method. To determine whether the precast piles may be reused, the survey on the integrity of the pile bodies as foundation members by the non-destructive test and the bearing capacity of the foundation by the loading test must be conducted in some cases.

One of the methods for roughly examining the states and positions of the damages of the underground piles is the non-destructive test. The non-destructive methods use low-strain elastic undulation, or earthquake generating equipment installed at the top of the pile produce vibration or an impact given on the top of the pile to measure the force exerted and vibrations. Another

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method, where various types of sensors are inserted into a bore holes formed in the hollow portions of the piles or in the piles themselves, or inspection windows previously formed during construction, may be included in the non-destructive test.

Table 1.3.1 Underground survey method (mainly pile foundations, see Annex 1)

Method Description Drilling survey Visually checks the states of foundations. Leveling survey Measures inclination or differential settlement of

underground foundations and others. IT test (PI test) Surveys the integrity of the pile bodies by carefully

hitting the heads of piles. Borehole camera Observes piles through their hollow portions, boreholes,

and gaps/cavities and others. Borehole radar Surveys the positions of damages in the piles, if any,

through boreholes and others. Borehole sonar Surveys the integrity of pile bodies through the boreholes

and the hollow portions of the piles. Ultrasonic measurement Surveys the integrity of pile bodies through the hollows

of the pile bodies. Caliper logging Measures any variation in diameter of minute holes of the

hollow portion at the cracks or cross sections of pile bodies. Used in conducting the surveys on damages/integrity through the hollow portions of piles.

Gamma-ray density logging Identifies gaps, if any, in the concrete elements using the dependency of the result of measuring the gamma-ray dose density. It is difficult to detect such a variation in density that may be caused by a crack.

AE measurement (acoustic emission)

Detects damages to pile bodies, if any, through an elastic wave induced by a crack.

Inclinometer Used in estimating the positions of the damages to pile bodies based on L-discontinuous points for inclination.

Loading test Estimates bearing capacity (static, quick, impact, etc.) Others Estimates the positions and sizes of the damages through

surface wave measurement.

(1) Survey from the heads of piles IT test. This method uses elastic undulation in a low-strain region to estimate the lengths and

damaged portions of piles based on the profile of its reflected wave. If a survey can be conducted on the piles after being removed from the footing, the result may be easily obtained. In contrast, even if the piles remain attached to the footing, this method enables the test to be conducted.

With the footing attached to the tops of the piles, an impact is generally applied on the footing or the anchors installed on pile heads. With the pile heads being not open, a signal reflected from the lower portion of the pile, as well as a signal reflected from the footing or

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column in the upper part is mixed into the resulting signal. Alternatively, another method (stereo measurement method) may be used. This method involves the following steps: 1) installing sensors at two test points on the piles, 2) separating a falling wave and arriving wave based on the phase contrast between elastic undulations measured at these points, and 3) evaluating the integrity of the piles based on information from the arriving wave.

(2) Survey through the hollow portions of piles The non-destructive tests conducted from the heads of piles, such as the IT test, is

effective as a primary method for estimating actual states of the damages to pile bodies. In some cases, however, any more direct method for grasping the damaged positions and the actual states of damages is required.

Various types of measurements may be conducted through the hollow portions for precast piles and core holes formed in the pile bodies for cast-in-place piles, respectively, which gives deeper insight into the actual states of the piles. These survey methods, however, are generally effective only when the heads of piles are open. If a footing or any other member has been constructed, boreholes need to be drilled in it. In this type of measurement method, sensors (or cameras) and others are inserted into the hollow portions of piles, where measurements are conducted.

In this method, 1) borehole cameras, 2) inclinometers, 3) gamma-ray densiometer, 4) caliper (hole or diameter) gauges, 5) ultrasound (acoustic intensity) measuring devices, 6) borehole sonars, etc., may be used. When the devices listed in 2), 3), and 4) are used, the sensors should be brought into contact with the sides of the holes and then slid on them for measurement (Photo 1.3.1, Annex 1).

One, which allows for most direct measurements and give distinctive results, is

observation of hole walls using 1) the borehole cameras. The borehole camera is a kind of video camera and several types have been developed including those integrating a fiber scope. Some enables measurements at an angle of 360° all at once. If the boring step is required in making measurement on the cast-in-place piles and others, the states of the concrete elements may be determined to some degree by observing core samples collected. Cracks, however, may occur in

Fig. 1.3.1 Example of a survey on the underground foundation (borehole camera, IT test, and bore sonar)

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boring and thereby, it is difficult to correctly distinguish between the cracks caused by the earthquake and those occurring later by boring in some cases.

If there is no information about the construction of pile or foot foundation, methods like the borehole radar and surface wave exploration should be used and after a rough inspection with these method, the integrity of the piles need to be checked by another method.

Some of the individual survey methods are described in Annex 1. See “Damage to Building Foundations and Their Restoration” (Kenchikugijyutsu, 1995, Special Issue, 1) and other literatures as the need arises. 1.4 Survey on Bearing Capacity

Possible causes for differential settlement of buildings and the damages to the pile bodies, is insufficient bearing capacity. Once differential settlement has occurred, the loading test may be used to ensure the direct understanding of the bearing capacity of existing piles.

In some cases, before the loading test on the existing piles, the load supported by the piles must have been temporarily up borne by some way. In the commonly used method (the steel pier technique), steel pipe piles are pressed into the bearing stratum using jacks by means of reactive force from the footing to support the load applied on the footing. The reactive force will be supported by the load on the footing and the piles in the vicinity of it in the loading test.

Photo 1.4.1 shows an example of the static loading test, which is most commonly used. The loading test includes the static loading test (the reactive pile method), as well as the rapid loading test and the impact loading test. Among them, the test, which recently has attracted attention, is the rapid loading test. Photo 1.4.2 shows an example of the rapid loading test, where almost all the load－displacement relations may be obtained.

Photo 3.4.3 is referred only for reference instead of exemplification. In this figure, a kind of pile construction method commonly used in China, by which piles are pressed in by applying static force. In the case where the pile diameter is small, it may be possible to conduct the test under press-in force for complementing the loading test. The steel pier technique commonly used in restoring the settled pile foundations is similar to this static steel pier technique, by which the bearing capacity is estimated, confirmed, and managed based on the relation between the press-in force and the amount of settlement and other parameters, if applicable.

載荷装置(5000kN 級) 載荷装置(50000kN 級)

Fig. 1.4.1 Vertical loading test on repulsive force piles (see Annex 2-1)

Loading equipment (5000kN class) Loading equipment (50000kN class)

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1.5 Evaluation of degrees of damages 1.5.1 Outline

The integrity of the building foundations is basically evaluated by checking for any differential settlement or inclination of buildings and for any crack or defect in their foundations. The parameters including an angle of inclination and a crack width may be used.

The criteria for determining whether any defect has occurred are applicable only to the members, on which visual check may be easily done, such as the raising portions of the continuous footing foundation of a detached house. For underground piles, it is important to evaluate their integrity and the degree of damages to them depending on the type of piles. Similarly, for pile caps and foundation slabs, may need to be evaluated considering the type of piles, the location of piles, and the effects of the technique used for attaching the pile heads.

As an institutional method for evaluating the degree of damages and severity of disaster damages to foundations, an evaluation method using the parameters such as the state and angle of deformation of foundation and the state of settlement in surrounding ground as indexes has been proposed for determining rapidly the risk level and severity of disaster damages of buildings after an attack of earthquake.

Only a few studies have been conducted on the degree of damages to the underground slabs and piles of buildings and thereby, definitive data is almost not available.

モンケン

クッション材

H

試験杭

GL

光学式変位計 OD-SYSTEM

光学式変位計ターゲット

杭体内歪ゲージ

加速度計

動歪ｱﾝﾌ゚ ﾌ゙ ﾘｯｼ゙ ﾎ゙ ｯｸｽ ADｺﾝﾊ゙ ｰﾀ

ADｺﾝﾊ゙ ﾀー

ロードセル

500tf実施例

モンケン５ｔｆ

チェラストバッファー

（緩衝材）

ロードセル

（１０００ｔｆ）

光学式変位計

（ターゲット部）

杭体内応力

Fig. 1.4.2 Example of the quick loading test method (see Annex 2-3)

Monogen

Pile strain gauge

Accelertor

Load cell

Cussion material

Bridge box

Dynamic strain amp

AD converter

Optical displacement gauge target

AD converter

Optical displacementgauge CD system

Test pile

Cellasto buffer

Load cell (1000tf)

Optical displacement gauge

Pile stress

Exampleof 500tf

Fig. 1.4.3 Static steel pier technique (Push piles, Shanghai, China)

13

It should be noted that it is possible to evaluate the degree of damages to building foundations and the integrity of them based on the state of piles and the result of structural calculation in a certain way, while unlike the foundations of structures constructed by public works, the necessity of restoration and recovery and the intent and degree of restoration may be dependent on a case-by-case basis in determining the severity of disaster damages to buildings and handling the result of determination. In the case where not only an earthquake but also settlement damages due to consolidation settlement have occurred, if the damages to the upper structures are not severe, inclination, if any, is perhaps restored only by replacing the floor materials with new ones to flatten in many cases because restoration of the settled foundations requires a large amount of money. Also, it should be noted that the pile heads are seldom dug out to make closer inspection unless serious building settlement or inclination occurs.

The guideline2) mentioned above assumes that the conditions (condition A) described below may be applicable to the buildings, of which foundations was damaged. For the buildings including those which satisfy the condition A, those for which settlement or inclination was detected in the rapid determination the dig-out survey it is require to be conducted.

Conditions which implicitly indicate damages to foundations 2)

1. Buildings situated in the area where a geotechnical flow due to the land slide or liquefaction was observed.

2. Buildings without being damaged, which are situated in the area where a earthquake with a magnitude of VI+ or larger attacked and their surrounding buildings were seriously damaged.

3. Buildings with an aspect ratio of 2.5 or higher, which are situated in the area where an earthquake of a magnitude of V+ or larger attacked.

1.5.2 Evaluation of degree of damages to foundation slabs

Table 1.5.2.1 and Figure 1.5.2.1 show the degrees of damages to foundation slabs. Any crack width was evaluated by ranking in four levels: 0.2 mm or less, 0.2 to 1 mm, 1 to 2 mm, and 2 mm or more. On the other hand, the severity of damages was evaluated by roughly ranking in five levels: rank I (mild), rank II (minor), rank III (moderate), rank IV (serious) and rank V (destructed).

14

Table 1.5.2.1 Scheme of degree of damages to foundation slabs 2)

Degree of damage

Symptoms

I ･0.2 mm or less of fine crack occurred. ･No concrete material fallen off.

II ･Approx. 0.2 to 1 mm of crack occurred. ･No concrete material fallen down. ･Concrete material slightly fallen off with reinforcing steels not visible.

III ･Approx. 1 to 2 mm of crack occurred. ･Concrete material very slightly fallen off. ･Reinforcing steels may be slightly visible.

IV ･2 mm or more of crack occurred. ･Concrete material significantly fallen off. ･Reinforcing steels seriously exposed.

V ･Reinforcing steels have bent and internal concrete structure collapsed. ･Foundation slabs deformed in the direction of its height. ･Settlement and/or inclination detected. ･In some cases, reinforcing steels broken.

15

1.5.3 Evaluation of degree of damages to pile foundations

Fig. 1.5.2.1 Example of degrees of damages to foundation slabs 2)

Degree Symptom

0.2 mm or less

Approx. 0.2－1 mm Minor peeled surface No reinforcing steel observed

Approx. 1－2 mm

Minor peeled concrete No reinforcing steel

2 mm or more of reinforcing steel observed

reinforcing steel not bent 2 mm or more

Reinforcing steel observed

Deformation in height Settlement/ inclination

Broken reinforcing steel

Internal concrete completely broken

Reinforcing steel bent and internal concrete completely separated

Broken reinforcing steel

16

Table 1.5.3.1 and Figure 1.5.3.1 show the scheme for evaluating the degree of damages

to cast-in-place concrete piles and examples of evaluation. As in the case of foundation slabs, crack widths were ranked at four levels: 0.2 mm or less, 0.2 to 1 mm, 1 to 2 mm, and 2 mm or more. Precast concrete piles (e.g., PHC piles), as shown in Table 1.5.3.2, were ranked at three levels: 0.1 mm or less, 0.5 mm or less, and 1 mm or less. Smaller crack widths were used in evaluating the degree of damages when the degree of damages were at the same level considering that the effects might exert on a prestressed, high-strength concrete material.

Table 1.5.3.1 Scheme for evaluating the degree of damages to cast-in-place concrete piles 2)

Damages due to axial tension

or bending (in the case where a crack has occurred at an angle of 45° to

almost the horizontal line)

Damages due to axial tension or shearing stress (in the case where a crack has occurred at an angle of 45° to almost the vertical

line)

Damages due to axial tension(in the case where only a

horizontal crack occurred)

I ･0.2 mm or less of fine bending crack (horizontal crack) occurred.

･0.2 mm or less of fine bending shearing crack (at an angle of 45°) occurred.

･One to three cracks occurred within 1.5D on one side. ･No concrete material fallen off.

･0.2 mm or less of fine crack occurred. ･One or more cracks occurred within 1 to 3D. ･No concrete material fallen off.

･0.2 mm or less of fine horizontal cracks occurred.

･Cracks occurred at an interval of approx. 1D or more.

･No concrete material fallen off.

II ･1 mm of horizontal crack occurred. ･Approx. 1 mm of crack occurred at an angle of 45°. ･One to three cracks occurred within 1.5D on one side. ･No concrete material fallen off, or only the surface material fallen off. ･Reinforcing steels not visible.

･Approx. 1 mm of fine crack occurred. ･One or more cracks

within 1 to 3D occurred.･No concrete material fallen off.

･1 mm or less of fine horizontal crack occurred. ･Cracks occurred at an interval of 0.5 to 1D or less. ･No concrete material fallen off.

III ･Approx. 1 to 2 mm of horizontal crack occurred. ･1 to 2 mm of crack occurred at an angle of 45°. ･Three or more cracks

occurred within 1.5D or cracks occurred at an interval of approx. 20 to 30 cm.

･Surface concrete material locally fallen off (approx. 10 cm in height, or within 0.2D)

･Reinforcing steels may be slightly visible.

･Approx. 1 to 2 mm of crack occurred. ･One or two cracks occurred within 1 to 3D. ･Oblique crack occurred

with concrete material fallen off from its top.

･Horizontal reinforcing steel not visible.

･Approx. 2 mm of horizontal crack occurred.

･Cracks occurred at an interval of 0.5 to 1D or less.

･Only 10 cm-width of concrete material fallen off along crack.

･Reinforcing steels are slightly visible through a gap left after concrete material was fallen off.

17

IV ･2 mm or more of horizontal crack occurred.

･2 mm or more crack occurred at a angle of 45°. ･Five or more cracks occurred within 1.5D. ･Cracks occurred at an interval of approx. 20 to 30 cm. ･Surface concrete material fallen off. ･Approx. 20 to 30 cm of

crack occurred or crack occurred within approx. 0.5D.

･Concrete material remains inside reinforcing steel members.

･Local buckling found in reinforcing steels.

･Vertical crack occurred.

･2 m or more crack occurred. ･Two or three cracks occurred within 1 to 3D. ･Concrete material fallen

off along oblique crack. ･Reinforcing steels are

visible along oblique crack.

･Buckling not found in reinforcing steels.

･Concrete material fallen off along crack (approx. 10 cm in width). ･Reinforcing steels exposed along gap left after concrete material was fallen off. ･Clearance left between pile head and footing, through which fixed concrete material is visible.

V ･Pile axially compressed. ･Concrete material broken down and buckling found in all the reinforcing steels. ･Reinforcing steels broken down.

･Buckling found in reinforcing steels along oblique crack. ･Vertically compressed. ･Reinforcing steels broken down.

･Buckling found in reinforcing steels. ･Axially compressed. ･Pile clinched. ･Reinforcing steels broken down.

Note) D indicates the diameter of a pile in the table.

18

Fig 1.5.3.1 Example of evaluation of degrees of damages to cast in place concrete piles 2)

Degree

Foundation slab Foundation slab Foundation slab Foundation slab Foundation slab

A

Foundation slab Foundation slab Foundation slab Foundation slab Foundation slab

1-3 cracks within 1.5D

0.2 mm or less

1-3 cracks within 1.5D

App. 1mm

Peeled surface, No reinforcing steel observed

3 cracks within 1.5D

Approx. 10 cm or 0.2D

Approx.1-2 mm

Local peeled concrete, reinforcing steel partiallyobserved

Peeled surface concrete

Vertical crack

Reinforcing steel partially bucked

All the reinforcing steel bucked

Vertically contracted

B

Pile foundation

C

0.2mm 1mm or less

Peeled concrete, No reinforcing steel observed

Approx. 1-2mm

Peeled concrete

Reinforcing steel observed, not buckled

Axially contracted

Reinforcing steel buckled, reinforcing steel broken

Foundation slab Foundation slab Foundation slab Foundation slab Foundation slab

Axially contracted

Peeled concrete Exposed reinforcing steel

Separated from footing, fixed reinforcing steel

Approx 2mm

Peeled concrete Approx. 10 mm (minor)

Reinforcing steel slightly observed

0.5-1D or less

1 mm or less

0.5-1D or less

0.2 mm or less Approx. 1D

Bent pileReinforcing steel buckled

2 mm or more

A=Damages due to axial force and bending force C=Damages due to axial force B=Damages due to axial force and shear force

19

Table 1.5.3.2 Scheme for evaluating the degree of damages to precast concrete piles (PC, PHC, PRC) 2)

Degree

of damage

Type of damage

Damages due to axial tension or bending stress. (in the case where crack occurred at an angle of

horizontal line to almost 45°)

Damages due to axial\tension or shearing

stress. (in the case where crack

occurred at an angle of 45° to almost vertical line)

Damages due to axial tension.

(in the case where only horizontal cracks

occurred)

I

･0.1 mm or less of fine bending crack (horizontal crack) occurred. ･0.1 mm or less of fine

bending shearing crack occurred (at an angle of 45°).

･Two or three cracks occurred within 1.5D on one side. ･No concrete material fallen off.

･0.1 mm of fine crack occurred. ･One or more cracks occurred within 3D on one side. ･No concrete material fallen off.

･0.1 mm of fine horizontal crack occurred. ･Cracks occurred at an

interval of approx. 0.5D or more.

･No concrete material fallen off.

III

･Approx. 1 mm or less of horizontal crack occurred. ･Approx. 1 mm or less of crack occurred at an angle of 45°. ･Three or more cracks occurred within 1.5D on one side. Or, cracks occurred at an angle of approx. 20 to 30 cm or less.･Local surface concrete

material may be fallen off (10 cm in height or within 0.2D).

･Steel material may be slightly visible.

･0.5 mm or less of fine crack occurred. ･Three or less cracks occurred within 3D on one side. ･No concrete material fallen off.

･Approx. 1 mm of horizontal crack occurred. ･Cracks occurred at an

interval of 0.5D or less. ･Concrete material slightly fallen off along crack (10 cm in width).

V

･1 mm or more of horizontal crack occurred.

･1 mm or more of crack occurred at an angle of 45°.

･0.5 mm or more crack occurred. ･Three or more cracks occurred within 3D on one side.

･Concrete material fallen off along crack (10 cm in width). ･Steel material exposed

along gap left after

20

･Five or more cracks occurred within 1.5D on one side. ･Cracks occurred at an interval of 20 to 30 cm or less. ･Local buckling or breakage found in copper material. ･Vertical crack occurred. ･Pile axially compressed. ･Concrete material broken down.

･Concrete material fallen off along oblique crack.

･Buckling or breakage found in steel material along oblique crack. ･Pile axially compressed.

concrete material was fallen off.

･Clearance formed between pile and footing, through which fixed reinforcing steels are visible. ･Buckling or breakage

found in steel material. ･Pile axially compressed. ･Pile clinched.

2. Restoration and reinforcement of building foundations 2.1 Outline

To restore and reinforce foundations, first of all it is necessary to determine whether the damaged elements will be restored for reusing, whether they are replaced with new ones, and whether the damaged elements will be left with no restoration for retrofitting using additional piles. If differential sedimentation occurred, needs to be corrected. For the foundations, the restoration of damages are usually done in parallel with the correction of differential sedimentation without an exception of repairing works on the raising elements of foundations and cracks and defects on foundation slabs because the differential sedimentation occurs in most cases.

Generally, the foundation members (composed mainly of concrete) are repaired in the same way commonly used as that for the structural members on the ground. On the other hand, at deep points under the ground, usually, repair works are not easily done and thereby, the use of additional piles may be basically useful in repairing when the members have been apparently damaged. If no other methods are available, such a method may be used that the surrounding area around the damages member is compacted by improving the ground (e.g., the grouting technique). This method is difficult to apply to structural computation and usually, is considered to be a quick fix or reserve-capacity one. Resin injection (the automatic low-pressure grouting technique) may be essentially used in repairing cracks in concrete materials and cross-section repairing with high-strength mortar or concrete in repairing defects. In some cases, however, steel pipes are attached to the damaged piles to restore or reinforce depending on the degree of damages and the type of piles.

The methods for restoring settlements may be classified mainly into two: jack up and grouting. Herein, the outline and basics of settlement restoring methods will be described. The

21

individual rearing, reinforcing, and settlement restoring methods are introduced in Annex 3. In addition, they are also described in References 1 and 2.

2.2 Repair, retrofitting, settlement restoration

To restore damaged foundations, various types of methods are used depending on the factors, such as the foundation form, building size, and desired restoration level, especially mainly on the foundation form (pile foundation/direct foundation).

It is unlikely that broken direct foundations lead to functionality deterioration even if the foundation members themselves incline to the same extent as in the case of pile foundations. In many cases, insufficient bearing capacity tends to incline the entire building together with its foundation and therefore, differential sedimentation needs to be restored from the standpoint of the functionality and dwelling performance. Expectation on restoration considerably varies on a case by case basis. To restore the settled buildings, the most commonly used methods are jacking-up or grouting and the level is adjusted to use the existing bearing layer with no modification. In some cases new piles may be used, depending on the state of the ground.

In the case where the buildings incline with minor damage, a simple method, by which the upper part above the foundation of its settled portion is jacked up and mortar is filled in clearances, or a method, by which differential sedimentation is restored using the grouting technique. On the other hand, in the case where settlement or differential sedimentation is severe with many cracks in the foundation, the upper side of the foundation may be jacked up construct a new foundation. If it is difficult to jack up the foundation due to the site condition or any other factor, it may be jacked down to adjust the level. Note that methods for restoring settlement commonly used in foreign countries are introduced in Section 2.5. Among them, one of the methods used in China involves digging out soil under the foundation on the raised side (on the not-settled side) by boring to restore to the horizontal level. To prevent middle size of detached houses and RC buildings from settling in the future, new piles are pressed into the ground to modify the form of the foundation. To press piles into the ground for stabling the entire ground under the foundation by means of improvement, various methods are used; for example, 1) actual piles are used, 2) mortar is injected into the ground to form pile-like cement bodies, small-diameter of steel pipes are pressed into the ground, or 3) post ground improvement (in the methods 1) to 3), virtual piles are used). The jack-up and grouting techniques are described below.

4.2.1 Jack-up technique

The jack-up technique, by which buildings are lifted, is the most used method for restoring the settled buildings and may be classified into several groups depending on the size of a building, site conditions, actual damages, and actual factors. The jack-up technique involves lifting up the settled portion of a building or the entire building using jacks literally. Hydraulic jacks are commonly used. The jacks with capacity two to three times the building load should be correctly inserted so that the same level of post load is applied on each of jacks. The jacks are usually inserted beneath the foundation footing supporting the posts. In some cases, however, they may be inserted beneath the underground beams. A special important factor is the capacity and arrangement of jacks to be used.

22

For jacking-up the building, reaction force is requiring. The reaction force can be obtained in three ways described below depending on the size of a building and the ground state around it:

1) The existing foundation is used as reaction force as it is. 2) A mechanical jacking is used to ensure reaction force. 3) New piles are pressed into the ground to ensure reaction force. The method 1) is used to easily and speedy restore settlement in the relatively small-sized

buildings (detached houses, steel-structured warehouses, etc.) with minor damages. This technique does not restore substantially the settled building and thereby, the building may settle again depending on the cause of the initial settlement. The method 2) is useful in the case where the ground around the settled building is relatively stable and the possibility of resettlement is low. The method 3) is used when reaction force can not be ensured on the existing foundation or ground, or when future settlement needs to be prevented in any way possible.

The most commonly used method for restoring differential sedimentation of buildings using jacks is the steel pier technique. This technique involves a process, in which steel pipes with φ 200 to 400 mm in diameter, 1 m in length, are pressed into the ground one after another, up to the bearing layer using the building load as reaction force. It may be assumed that 1/2 to 1/3 times the maximum press-in force is set for long-term permissible bearing capacity. When the piles are pressed into the ground, the pressing-in force can be read using a manometer. This means that the technique has an advantage in that most of bearing force may be verified as in the load test (note that it is not complete unlike the standard load test). Moreover, construction is made only under the foundation and thereby, the building can be used as usual. The working space under the foundation is about 1.5 m.

Photos 2.2.1.1 and 2.2.1.2 show the states of the steel pier technique and the building restored by this technique in Niigata Earthquake in 1964. Photo 2.2.1.3 shows the building restored by the mechanical jacking technique.

In addition to the steel pier technique, typical jack-up techniques include the techniques of mechanical jacking, saddle technique, shed restoration technique, and nekagami technique, of which outlines are described in Fig. 2.2.1.1. For more information, refer to Annex 3 if necessary.

Photo 2.2.1.1 Example of construction by steel pipe press-in technique

23

Photo 2.2.1.3 Example of settlement restoration by pressure board technique The ground in the vicinity of the periphery of the building was dug out and concrete was cast on a suitable natural

ground. Then, jacks were inserted between the concrete board and the bracket attached to the side wall of the periphery of the foundation to lift the foundation.

Photo 2.2.1.2 Examples of settlement restoration by steel pier technique and lifting technique Examples of settlement restoration of direct foundation type buildings settled by an

attack of Niigata Earthquake by steel pier technique while being used. As a part of construction management in settlement restoration, any vertical and horizontal displacement was automatically

measured using a slide meter and a seismometer.

24

Fig. 2.2.1.1 Outline of jack-up technique (Supplied by: Mase Construction)

Steel pier Pressure board Sandle

Shed restoration Negarami

Support jack Hydraulic jack Hydraulic jack

Pressure board

Steel pipe piles are cast to reinforce the foundation and use as a repulsive force in restoration. Prevents re-settlement from occurring.

Concrete board (pressure board) is cast under the foundation to use as a repulsive force in restoration.

In many cases, used for prefabricated and reinforced concrete houses. Uses the ground as a repulsive force in restoration.

Base

Bracket

Reinforcing steel post

Negarami steel

Hydraulic jack

Often used for buildings constructed by conventional methods such as timbered axis. Note that it is prerequisite that the ground is stable.

Often used for large-scale reinforced concrete buildings (factories and warehouses). It is also prerequisite that the ground is stable.

25

2.2.2 Grouting technique

Most of restoring techniques basically involves a mechanical process for lifting the foundation up using jacks, ensuring high certainty. In some cases, the grouting technique, by which grout is injected into the ground for raising it, lifting the building, is also used for direct foundation buildings. This technique has a reduce reliability and certainty; however, it may be useful when easy and speedy restoration is required. The grouting technique is largely classified into two types: in one type, the grout is permeated into the ground and in the other type it is solidified by itself without permeating. To improve safety of the entire foundation ground, the former may be used under the foundation or around piles. To restore differential settlement, the latter is suitable. Cement grout is used as grout because of its excellent durability (Photo 2.2.2.1). The chemical grouting technique involves a process for injecting a chemical (for jacking up, cement flash-set chemical), which requires a given time for curing when injected, to compact the ground (the chemical can not permeate into the viscous soil layer and thereby, it enters into the ground in the form of nervation). Recently, a new grouting technique has been put into practical use by which highly illiquid grout with a slump of almost zero is pushed into the ground under high pressure (Photo 2.2.2.2).

To restore differential settlement by grouting, it is required that the impermeable grout be pressed into the ground on the depressed side to increase the volume of the ground causing the ground to rise. This results in the raising ground. In the chemical grouting technique, several grouting works are used. To restore settlement, the simple rod technique or the double packer technique, which allows for close construction management, is used. The chemical is in a liquid state and has high fluidity, when injected, even if an impermeable one is used and therefore, it tends to travel in the form of nervation or layer. Accordingly, it is difficult to artificially control the degree to which the ground is raised. Depending on the ground condition, no effect of grouting is observed.

On the other hand, unlike chemical grouting, in compaction grouting, illiquid (slump being almost zero) cement mortar is pushed into the ground under high pressure (approx. 100 kgf/cm2 of max. discharge pressure) and so, it is unlikely that the grout travels in the form of nervation or layer and a mass (bulb-like) of cemented bodies are usually formed. Note that if the ground, into which the grout is injected, is heterogeneous, the injected grout deforms. Since for the grout is hard to travel out from a given area, the degree to which the ground is raised can be easily controlled. Accordingly, the settled building may be restored if construction is carefully made while the lifting condition and effects of lifting on the periphery of the building are being monitored. Determining from the past results, the foundation form, to which compaction grouting is applicable, is the direct foundation (especially, raft foundation). For a larger size of building, the vertical load under the foundation is also large. This means that the ground tends to expand laterally when the foundation is raised. In this case, simply the ground around the building may be raised without the building itself being lifted. This technique is only applicable to a moderate size of buildings.

It should be sufficiently noted that compared with the jacking up technique, the grouting technique has an advantage in time for completion and construction cost, while depending on the ground condition/foundation form/size of building, no effect of grouting is expected. It is required to consider the ground environment because: 1) the grout may enter the neighboring sites across the boundary; 2) a water survey is conducted when a grouting work is made in the

26

civil engineering field, and 3) it is difficult to conduct the ground survey or evaluate the ground itself when the site is reused for housing rehabilitation.

Photo 2.2.2.1 Example of settlement restoration using cement grout The direct foundation-type of building is being restored from settlement by injecting a cement

grout.

Photo 2.2.2.2 Example of compaction grouting The direct foundation type of building include due to liquefaction caused by an earthquake is being restored by compaction grouting. Some of Slamps 2, 3, and 4 is used for the grout. This is an example pf applying compaction grouting to a Japanese house. This technique has not been usually used in settlement restoration in Japan.

27

2.3 Restoring the settled detached houses

For the detached houses, basically, the steel pier technique is used to restore settlement (Photos 2.3.1 and 2.3.2). In the case where the continuous footing foundation has been used, the working space can be ensured by digging a fox hole. For the raft foundation or the foundation with piles jointed, construction is difficult and careful attention must be paid because of working space and steel pipe arrangement. The form of the foundation after the steel pile was pressed in resembles a pile foundation (since rolling compaction under the ground is difficult, almost no ground bearing capacity can be expected). Depending on the interval between steel piles, the foundation needs to be reinforced.

The grouting technique (Photo 2.3.3) is also used in some other cases. Since no design and construction methods for grouting have been established, its effects may vary on a basis of case-by-case and improvement of design and construction methods and accumulation of data is required. Compared with the continuous footing foundation, the raft foundation is easily lifted. If the periphery of the building is surrounded to limit grouting to the inner area, this technique is useful. On the other hand, it is also important to discuss the effects on the surrounding environment (the grout may travel the neighboring sites and enter the discharge layer of the backside of the retailing wall) and the ground environment.

Furthermore, it is also important that the cost of settlement restoration varies depending on the conditions such as design/construction techniques and the assurance system to be used.

28

(f) Inclination measurement instrument (g) Joint (h) Vertical precision management (i) Loading test Fig. 2.3.1 Steel pipe press-in technique for detached houses

(d) Joint welding (e) Pressed-in steel pipes

(a) Panorama view of test site

(b) Used steel pipes (1 m in length)

(c) Pressure management

29

Photo 2.3.2 Steel pier technique for detached houses

(b) Steel pipes used by steel pipe press-in technique

(c) Steel pipe head treated

(a) Steel pipe pressed into the ground under the foundation

Photo 2.3.3 Example of settlement restoration by steel pier technique for detached houses By injecting flash-set type cement grout, a detached timbered house is lifted. The construction management is performed using an auto level in settlement restoration.

30

References 1）Foundation and Method of Restoration of Damaged Building, Masahito TAMURA, Kenchiku Gijutsu, vol.9, 1995. 2）Damage Grade Classification Manual of Building Foundations and Some Examples of Repair Techniques by Mikio Futaki, Takashi KAMINOSONO and Shinsuke NAKATA, Kenchiku Kenkyu Shiryo vol.90, Building Research Institute, 1997.8

1

Annex 1 – Integrity Investigation Techniques

1. Borehole radar 2. Borehole radar II 3. Borehole sonar I 4. Borehole sonar II 5. Cavity/Gap investigation 6. Elastic wave test on pile integrity 7. Ultrasonic test on pile integrity 8. Inclinometer test on vertical pile precision 9. Borehole camera test on pile integrity 10. Surface wave search I 11. Surface wave search II 12. Carbon fiber monitoring technique for pile integrity 13. Optical fiber pile damage detection system 14. CT scan quality evaluation

2

1. Borehole radar I

Measurement of interval between foundation piles of bridge base by inserting borehole antenna Two-way antenna reflection measurement Double antenna cross hole measurement transmission type TUBEWAVE100 type antenna: Center frequency 100-400 MHz, antenna mass weight approx. 2 kg, outer diameter 37 mm, length 1200 mm

References: Toshioka, Nakamura et al: Examples of borehole radar search for bridge base foundation piles, 104th Academic Presentation Proceedings, Society of Exploration Geophysics of Japan, 2001

Data supplied by: OYO Corp.

Tim

e[ns

ec]

Oblique distance [m]

Opening

Opening

Channel Channel A

A A A

(Road)

Bridge base

Byway

B

B

Byw

ay

(bridge base)

Estimated foundation pile position

Unknown buried structure

E

D

A=road B=embankment C=boring hole D=planned route by promotion/management E=oblique boring, 21.0m in length F=vertical boring, 12m in length G=amplitude H=To control cable (to instrument main body)

F

Planned magnitude of earthquakeΦ

850mm GL-10m

Unknown buried structure

Brid

ge b

ase

(Road)

Fig. 21 Borehole radar configuration and measurement schematic diagram

Display Instrument main body

Center Antenna

Instrument (SIR-10H)

Earth surface

Borehole antenna

Bottom

Oblique distance Opening

Tim

e G

Bridge base

H

Hole bottom Ti

me[

nsec

]

Oblique distance [m]

Hole bottom

C

3

2. Borehole radar II

The investigation bore is drilled in the vicinity of the target structure (0.5-1.0 m) and PVC VP65 (inner diameter, 65 mm) for hole wall protection is cast to insert the radar. Measurement accuracy is improved by measuring the degree of curving of the hole. approx. 230 MHz, interval between antennas: 1200 mm, diameter of measurement tube: 50 mm, 2300 mm in length measurement depth: up to GL-30 m, measurement: 10-20 cm The searching accuracy deteriorates in the order of steel pipe pile/steel pipe plank, precast concrete pile, cast-in-place pile, and wooden pile.

Data supplied by: Kiso-jiban Consultants Corp.

Optical cable Transmission antenna

Fig. 2.1 Circuit configuration

PC

Timing pulse generator

Transmitter

Amp

Receiving antenna

Coaxial cable

Trigger

Oscilloscope

Photo 1. Bore measurement tube

Photo 2. Being measured (right)

A

B

C Fig. 2.2 Radar waveform

(Upper: straight hole, Middle: in the vicinity of searching area, Lower: oblique hole) Photo. 3 Being investigated

Enlarged drawing

3. Example (steel pipe pile Φ300mm)

depth(m)

A=delay in optical cable B=delay in coaxial cable C=trigger delay in oscilloscope

4

3. Borehole sonar I

The sensor is inserted into the boring hole formed in the foundation pile or improvement member, or the investigation hole formed at the construction stage and radial diameter and shape are estimated at a given depth to evaluate the pile integrity.

Reference: Tamura, M.Futaki, and A.Abe,: Use of Non-destructive method for the evaluation of reclaimed soil-column、 IS-Tokyo 96, 1996. 2nd international conference of Ground Improvement

5

4．Borehole sonar II

Investigation of pile shape for enlarged cast-in-place concrete bottom The enlargement of the bottom is estimated using the sensor vertically inserted and actual measured values are

compared. Experimental overview: piles to be tested (enlarged-bottom piles: plain type Fc＝18N/mm2）, elastic wave

velocity Ｖp≒4000m/s（actual value） Data supplied by: TAKENAKA Corp.

反射波測定

直達波測定

発信制御部

孔壁圧着装置

測定ケーブル

窒素ガスパイプ

200

30 発信子

反射波受信子 直達反射波受信子

圧着ピストン

圧着プレート

Pressure plate

A

B Receptor

Reflected wave receptor

A=pressure piston B=direct reflected wave receptor

Measurement cable

Nitrogen gas pipe

Reflected wave

Hole wall pressure device

Direct wave measurement

Wave trans. control

Fig.7 Waveform at each depth

Rel

ativ

e pa

rticl

e ve

loci

ty

Time Fig. 6 Example of measured waveform (N direction)

6

5. Cavity/Gap investigation (CCD camera, fiber scope）

Investigation of the presence of cavities or cracks in the concrete layer, checking for any gap between the concrete layer and its surrounding ground, back filled concrete, observation of the improvement member and outer surface of the concrete core through the investigation hole with no core, quality check of damaged pile bodies CCD camera (φ25 mm）, micro CCD camera (φ12 mm) Industrial fiber scope (φ13 mm, length:6 m)

Data supplied by: Kiso-jiban Consultants Corp.

Example of cracks

Example of hole

2)CCD camera (outer diameter: Φ25 mm)

1) Cavity/gap investigation device

Upper: CCD type Lower: scanner type Right: CCD type enlarged tip

3) Micro CCD camera (Outer diameter: Φ12 mm)

4) Industrial fiber scope (Outer diameter: Φ13 mm length: 6 m)

7

6. Elastic wave test on pile integrity

Method: Integrity test (IT test, PI test) The test technique using elastic wave with low strain for checking pile integrity are called the integrity test or low strain test method and it is one of non-destructive tests. A sensor is attached at the pile head and then the pile head is gently hit to generate elastic wave. The elastic wave reflects at the top of the pile and the length of the pile may be estimated based on the time when the reflected wave reaches back the starting point. Since if any defect or crack is detected in the cross section, an elastic wave reflects at the point, abnormal point may be detected. An accelerometer is commonly used as the sensor. For buried piles, the test may be conducted directly after the construction, while for cast-in-place piles it can be conducted only approx. 24 hours after construction because the strength of them must reach the level at which the test can be done. In the test for determining whether the piles may be reused, no accurate result of the test may be obtained for long piles because of their periphery friction resistance in some cases. The characteristics and differences of waveforms may be understood by carrying out the test on all the piles. When the test is carried out with the slab or structure on the precast pile, it is required at least to attach a sensor directly on the pile body; otherwise the effect of the upper structure is reflected in the result of measurement. Alternatively, by attach two sensors on the pile at the different depths to use a difference in waveform phase recorded by each sensor, any effect of the upper structure is offset and only the reflection from the lower structure may be extracted. Data supplied by： Tokyo Soil Research Corp.

打撃

鉄筋等

ボイド管等

センサー

杭

ＴＩ

打撃時

先端反射

Impact Steel member

Wave reflected at top

Accelerometer Hammer

Void tube

Sensor

Pile Rel

ativ

e ve

loci

ty a

mpl

itude

Impacted

Pile length (m)

PV

Measurement instrument

Impact

8

7. Ultrasonic pile integrity test

Method: Ultrasonic wave quality evaluation of pile bodies and structures (Ultrasonic wave) The oscillator and receptor are inserted into the measurement holes to measure ultrasonic wave for evaluation of the quality of pile bodies and the presence of defects in cross sections. In European countries such as England and Netherlands, is known to be the cast-in-place pile quality evaluation technique, however, in Japan, less tests have been carried out. The method include two types; the single hole method, by which one measurement hole is used and the multi-hole method, by which several holes are used. In the former, the oscillator and receptor are inserted at a depth of approx. 1 m to examine the actual state of concrete layer in the vicinity of the measurement hole. In the latter, the presence of defects in the cross section may be detected by forming measurement holes in the vicinity of the pile. Data supplied by: Tokyo Soil Research Corp.

測定管

受信子発信子

杭

プリアンプ

測定装置本体構真柱

鉄筋かご

測定管③

測定管② 測定管①

測定管④

杭

AB

Initial vibration t1

A=initial vibration t0 B=propagation time T

Concrete strut

A

Reinforcing steel net

A

A A

A

A=measurement pipe

Pile Oscillator Receptor

Pile

Instrument main body

Preamp

9

8. Inclinometer test on vertical pile precision

Method: Investigation of precision of pile casting and check for bent points of piles under ground using a inclinometer.

By inserting the inclinometer in the hollow part of the buried pile, not only the precision of pile casting may be evaluated but also the presence of bent points of piles may be verified based on summed inclined angles. By detecting disconnecting inclination points, the damaged points may be fund. At present, to insert the inclinometer in the hollow part of the pile, the spring-activated system for pressing a plate and the pantograph system for pressing a rod.

Data supplied by: Tokyo Soil Research Corp.

Inclined angle

Depth

10

9. Bore camera pile integrity test

Method: Borehole camera pile observation A hole is formed in the pile using an excavator, a CCD (Charge Coupled Camera) camera is inserted in the hole, and the quality of the pile and the actual damages to it such as cracks are observed directly from the inside of the pile in real time through the monitor screen of the instrument. The acquired image data are always recorded in the recording device. At present, several types of borehole cameras are used, largely classified into three; BIP (Borehole Image Processing) system, BSM (Borehole Scanner type M) system, PIC (Profile Inspection Camera) system. Data supplied by: Tokyo Soil Research Corp.

Crack

BIP System

ビデオ収録

音声入力 映像入力

映像入力

マイク

ＴＶモニター６インチＴＶ８㎜ﾋﾞﾃﾞｵﾚｺｰﾀﾞ

内蔵

コード

杭

体

370

73

水中ライトカバー

カメラ本体

ジョイステックコントローラー（カメラレンズ回転操作フォーカス調整）

カメラレンズ（回転可）

（単位：㎜）

BSM 方式のボアホールカメラ

BSM System P.I.C

Cord

Mic F

Pile body A B

Cove C

D

G

E H

I

A=camera body B=camera lens (rotary) C=underwater camera D= unit (mm) E=audio input F=TV monitor, 6in., internal TV 8 in. video recorder G=video recording room H=image input I=joystick controller (camera lens rotation, focus adjustment)

Compound cable

Direct control unit

Compound cable

Compound cable

Direct control unit

Direc. control unit ・Azimuth sensor

Fisheye lens

TV camera

Sonde

Sonde Camera Lighting fix.

Sonde Camera Lighting fix.

Crack Crack

Crack

Lighting fix Azimuth

Upper hole wall

Upper hole wall

Upper hole wall

Lower hole wall

Lower hole wall

Lower hole wall

11

10．Surface wave search I (Kakeya system, multi-channel)

The surface wave runs along the interface between the ground and the air. The propagation velocity of the short wave is affected by the effects of the shallow ground layer and that of the long wave by the deep ground layer. Thus, the surface wave develops such a phenomenon that variation in the propagation velocity occurs depending on the wavelength. This variation is determined depending on the distribution of S wave propagation velocities and therefore, by reverse-analyzing the wave phenomenon, the distribution of S wave propagation velocities may be obtained. Using the analyzer, which measures and analyzes data on vibration data at multiple points through multi-channel system, the 2D distribution of S wave propagation velocities may be easily output at the test site. It takes about 40 minutes to obtain the result of analysis after the measurement. Reference: Hayashi & Ijuin: Two-dimensional investigation of housing site using a surface-wave method, “Actual situation and issues of detached house foundation design” symposium, Architectural Institute of Japan, Feb. 2003. Data supplied by: OYO Corp.

起振 長い波長の表面波

短い波長の表面波

12

10

8

6

4

2

0

-2

-4

(m)

深

度

0 5 10 15 20 25

(m)距 離 程

(km/s)

S波速度

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

縮尺＝１／250

C B AD

5 10 15

2

4

6

5 10 15 5 10 15 5 10 15

Short-length surface wave

Long-length surface wave

Excited vibrations

Depth

Distance

S wave velocity

12

11. Surface wave search II (Exciter, Rayleigh wave）

Measurement method: An exciter and two detector are installed at measurement points and the ground surface is excited upward and downward. Upward and downward vibrations of the surface wave are detected by two detectors and based on the result, the Rayleigh wave component is calculated.

Method: Assuming that Rayleigh wave velocity=S wave velocity (Vs), a Vs-N value (standard penetration test value) or Vs – qu （single-axis compression strength） correlation equation is used to estimate geotechnical values for them.

Data supplied by： VIC Corp.

電力増幅器

A B

発

振

部

地

震

計

部

通

信

部

A/D 変 換 部

起振機 E

Power amplifier

B

A=Oscillator B=Seismometer C=A/D converter D=Communications unit

Exciter E

A C D

13

12. Carbon fiber pile integrity monitoring technique

Photo: monitoring sensor being attached to actual structure

Sensor attached to PHC pile Sensor attached to cast-in-place pile Attached measurement terminal box

20

炭素繊維束 ガラス樹脂シート

2

信号ケ－ブル

杭頭部

地震

テスタ

Carbon fiber monitoring sensor Explanation diagram of measurement using sensor

By an attack of South Hyogo Earthquake, so many underground structures such as piles were damaged. To verify

the damages to the piles, the method, which involves steps of excavating the ground and making visual check is usually used. This method requires a large amount of cost and long time and hereby, it is not useful if quick determination of the degree of damages is required. To solve this problem, a new technique, by which the degree of damaged to the piles may be rapidly determined immediately after the earthquake, has been developed.

A variation may occur in electric resistance of the carbon fiber with conductivity depending on strain when pulling force is applied. This variation is kept after the load has been removed. A sensor as shown in the figure above, which such a property of the carbon fiber is adopted, is attached to the point in the concrete layer where any damage to the pile head is predicted in advance. In addition, the signal cable is laid in the structure and the terminal box for resistance measurement is installed at an appropriate point. Then, after an attack of earthquake, the electric resistance is measured by testers to determine whether any damage to the pile head and if any, its degree.

This method has been applied to five cases. Base on these cases, the usefulness of this method is being verified in terms of attaching the sensor to precast piles, cast-in-place piles, and underground beams, and installing measurement system.

Kiyoshi ISII, Hiroshi INADA & Yoshihiro SUGIMURA: Development of Sensor using Carbon Fiber and Evaluation of Performance (Development of techniques for monitoring integrity of piles (Part I)), Journal of Structural and Construction Engineering (Transactions of AIJ), No.557, pp.129-136, 2002.7.

Hiroshi INADA, Kiyoshi ISHII, Yoshihiro SUGIMURA, & Kenichi SASAKI: Performance Evaluation of Carbon Fiber Sensor to Detect Damage to Piles (Development of techniques for monitoring integrity of piles (Part II)), Journal of Structural and Construction Engineering (Transactions of AIJ), No.563, pp.91-98, 2003.1.

Hiroshi INADA, Kiyoshi ISHII, Keiichi OKADA, & Yoshihiro SUGIMURA: Practical Application of Monitoring Techniques to Detect Damage to Concrete Piles, AIJ Journal of Technology and Design, No.18., pp.79-84, 2003.12.

Data supplied by: Shimizu Corp.

Schematic diagram：

Signal cable Carbon fiber flux

Glass resin sheet

Tester

Pile head

Earthquake

14

13. Optical fiber pile damage detection system

The system uses optical fibers to detect any damage to underground structures such as piles.

Any preset damages may be detected base on the states of optical fiber cutting mechanism and protection. Optical fibers are externally or internally attached t the pile heads (tend to be damaged) at four corners of a building to evaluate the degree of damages. The upper photo shows the detection reliability of the optical fiber sensor This is verified by attaching the optical fibers to the PHC piles and a bending test is conducted to measure the width of a crack.

Reference Tamura, Katoh, Teshigawara et al.: Damage Control Technology of Concrete Piles Using Optical Fiber (Part 1 Bending Test of A PHC Pile embedded Optical Fiber), Proceedings of the 35th Japan National Conference on Geotechnical Engineering, The Japanese Geotechnical Society, June 2000

15

14. CT scan quality evaluation

Summary: A medical CT scan device was used to examine the state inside the pile body or improvement member (deep

chemical mixing method (DCM)) and the applicability and reliability of this method was discussed. The result showed that the state of the pile head with defect inside might be correctly detected.

The specimen, which soil mass or slime was artifically inserted in the improvement member or concrete layer, was used in the experiment. The state of the crack inside the pile was completely consistent with the result of the vusual check on the cross section of the cut pile.

These results of the experiments demonstrated that when the soil mass or slime was solidified inside the pile, gap might be formed due to evaporation of water contained in it.

It should be noted that if any steel material is contained inside as in PHC piles, the result of CT scan beconme complicated due to reflection.

Reference Tamura, Ogawa, et al: The Quality valuation of mixed column by Electric Resistivility and CT Scan, Symposium of Architectural Institute of Japan, Oct.1999

(a) CT scan image (b) Cross section

1

Annex 2 – The Techniques of Restoration, Reinforcement and Settlement Restoration

1. Steel pier construction method 2. Steel pipe attach method 3. Steel pipe replacement, repress fit construction method 4. Simplified rising method, shed restoration method 5. Pressure resistant slab method 6. Grouting method I (Cement composite grout) 7. Grouting method II (Compaction grout) 8. Example: Restoration from settlement caused by Niigata Earthquake in 1964

2

1. Steel pier method

This method involves a step of pressing approx. 1.0 to 1.5 m steel pipe piles sequentially down to the nearing layer the self-weight of the building as a repulsive force. Steel pipes approximatelyφ100-φ200 in diameter are commonly used for detached houses.

The Kenchiku Gijutsu Issued in Sept. 1995 P.86-99 Data supplied by Mase Construction Co., Ltd. http://www.masecom.co.jp/mk

Steel pipe pressed in (A detached house)

Steel pipe pressed in (RC structure) Welding

A steel pipe

A hydraulic jack

Press-in

Existing foundation

3

2. Steel pipe attachment method

Longitudinally halved steel pipes are attached around the damaged part of an existing pile. Expand mortar is filled into the gap left between the existing pile and the attached steel pipes. You can start the construction process, you must have well maintained and repaired any cracks and/or defective parts of the existing pile.

Kenchiku Kenkyu Shiryo No.90 August 1997(Building Research Institute) P.53,P.68 The Kenchiku Gijutsu Issued in Sept. 1995 P.56 Data supplied by Mase Construction Co., Ltd. http://www.masecon.co.jp/mk

An existing pile Pile, around which halved steel pipes are attached

steel pipe longitudinally

Expand mortar being filled

Un-reinforced pile

A longitudinally halved steel pipe

A halved steel pipe welded

4

3. Steel pipe replacement, repress fit method

This method involves a step of removing defective part from the existing pile damaged only at its head and a step of replacing them with steel pipe. Then the pile is inserted into the ground using a hydraulic jack and the bearing capacity is confirmed to fix the pile head.

The Kenchiku Gijutsu Issued in Sept. 1995 P.56 Data supplied by Mase Construction Co., Ltd. http://www.masecon.co.jp/mk

Damaged bearings before the reinforcement work

A hydraulic jack

Re-press fit Steel pipes

Un-reinforced pile

5

4. Simplified rising method＋Shed restoration method

Part of the foundation around the base of a column settled down is chipped, a hydraulic jack is inserted there, and then the foundation is jacked up. This combined method is commonly used for the buildings constructed by the conventional timber axial construction method provided that the foundation is in a stable state. It has advantages in that the construction cost is lower and the construction period is shorter.

The Kenchiku Gijutsu Issued in Sept.1995 P. 110-111 Data supplied by Mase Construction Co., Ltd. http://www.masecon.co.jp/mk

Part of the foundation being chipped A jack inserted

The foundation jacked-up working state

The foundation restored from settlement

Sill

Jacking-up

Foundation A hydraulic jack

6

5. Pressure-resistant member method

This method involves: a step of constructing a RC structural pressure-resistant member under the foundation; placing a hydraulic jack on it; jacking-up an existing building together with its foundation. This method can be applicable to the firm ground because the plate is heavy and therefore, it does not have much of actual achievement records.

The Kenchiku Gijutsu Issued in Sept. 1995, P.100-101 Data supplied by Mase Construction Co., Ltd. http://www.masecon.co.jp/mk

RC structural pressure-resistant plate being cast

Temporary bearings

Jacking-up

An existing building

Jacking-up A hydraulic jack

A saddle

Pressure-resistant concrete plate

7

6. Grouting technique I (Example of cement grout)

Method: Eye lift technique (settlement restoration method using cement flash-set chemical liquid) 1) Gtouting sequence: Injecting grout into the layer under the foundation to be lifted up and then into the lifted-up layer to restore from settlement. 2) Grouting management: Mesurement devices such as a leveling tube are attached at four corners of the house to read automatically measured values during and after the construction, Successful achievements have been widely got in restoring settled houses using the cemenet grouging technique as mentioned above in Japan. The methods for grouting and manamenent depend on the working technique used. It should be noted that the effect of grouting depends on the grouting sequence and the amount of grout.

Data supplied by: Soil-Design Co., Ltd

A=[Grouting for bearing] B=Grouching machine C=Bearing Disk D=Bearing layer E=[Lift-up grouting] F=being grouted while lifting-up G=Grouting for foundation reinforcement H=Lifting disk

E

FC

D

B

A

G

H

8

7. Grouting technique II (compaction grout)

Supplied by: Sanshin Const

In foreign countries including US, thie method, which is also referred to as mudjacking or pressure grouting, is widely used for settlement restoration. Several centimeters slumps are used. The beiding degree of the guide tube is also an important indicator for smooth grouting. Reference: Tamura, Shibata et al.: Strengthening of Building Foundation by Compaction Grouting, Soil and Foundation, Vol.43, 1995

Guide tube

Lifting vector

Guide tube

Water valve

Pressure gaugeJack

Guide hose

Pressure gauge

Pressure piston

Jack

60 degrees

Diam. (mm)

Fig. 2 Altitudinal granularity distribution

Fig. 7 Experiment apparatus

Range of effect

Injection tank

Consolidated bodyFig. 1 Schematic of grouting

Table 2 Test resultA B C D E F

G

A=Composition B=Slump C=Amount of grouting D=Volume after grouting F=Volume after grouting G=Schematic

Tran

sien

t mas

s per

c. (%

)

9

8. Case of restoring the building settled by an attack of 1964 Niigata Earthquake

The case of restoring the building settled by an attack of Niigata Earthquake. In this case, the building was restred while the building was being used. This material is valuable in that the press-in, sunddle setting, and jacking-up processes may be visually recongaized. Automatic vertical/horizontal measurement management in restoring the settled building was performed using a landslip meter and a seismometer. Data supplied by: Ando Corp.

1

Annex 3 – Countermeasure Techniques Against Differential Settlement

1. Countermeasure against differential settlement (prediction, measurement, restoration, and alleviation) 2. Settlement restoration technique using steel bases 3. Hybrid foundation structure combining beating piles and a direct foundation 4. Control piles (Mexico) 5. Ground woks using light-weight materials 6. Principle of long/short pile hybrid foundation design

2

1. Countermeasures against differential setlement (prediction, measurement, restoration, and alleviation)

■ Sedimentation prediction technique A computer-based analytical method enables the mount of sedimentation to be predicted correctly and effectively. ■Automatic measuring technique of differential sedimentation There are the methods, by which a laser beam is received by laser fivers and a leveling tube is used to detect the degree of level. ■Differential sedimentation restoration technique This jack-up system enables the amount of differential sedimentation to be restored any time (during or after construction) by inserting the jacks between the upper structure and foundation of the building. ■Differential sedimentation alleviation technique Any countermeasure for alleviating differential sedimentation of the foundation/building is adopted and a system best suited for the characteristics of the building is incorporated in design.

Data supplied by: TAKENAKA Corp.

Hydraulic jack

Hydraulic unitLifting-up cart

●laser beam

● Example of measure for alleviating differential sedimentation

Central control panel Monitor panel

Central control panel Monitor panel

laser beam generator

Level measurement Laser beam receiver

Base Leveling tube method (patent pending) Water filling

valve

Sedimentation amount detector

Reference height detector

Leveling tube Base

Light-weight roof

Absolute RAMEN frame

Dry-worked external wall

Automatic measurement/restoration system of Differential sedimentation

Steel beam

Base Soil filled

layer

Sand compaction pile

Clay layer

Gravel layer

3

2. Sedimentation restoration technique using steel bases

To restore very soften ground with N value= 0 or 1 or new soil-filled ground, for which any other effective countermeasure against settlement can not be adopted from the techncal and economical standpoint, this method is often used. To facilitate jucking-up against differential sedimentation, steel bases are used instead of the standard type of bases.

Data supplied by: Sekisui House Corp.

4

3. Foundation Structure composed of beating piles and a direct foundation 1/2

基礎スラブ

支持杭

鉛直変位 杭頭反力調整装置

鉛直変位

鉛直荷重

ギャップ

鋼管杭

1500

028

0010

050

ひずみゲージ

支持層

二重スラブ

フィルサンド

フィルコンクリート

-19500

杭頭反力調整装置

フィルサンド

27600

GL

(単位: mm)

PN

杭頭反力調整装置Vertical displacement

Pile head repulsive force adjuster

Vertical load

Foundation slab

Pile head repulsive force adjuster

Bearing pile

Gap Vertical displacement

Fill concrete

Fill sand

Loading

Movable plate

Presser plate Fixed plate

Compacting force

PC steel rod

Fill sand

Double slab

Pile head repulsive force adjuster

Strain meter

Bearing layer

Steel pipe pile

Unit: mm

5

Hybrid Foundation Structure combining Bearing Piles and a Direct Foundation 2/2 1. Principle of hybrid foundation combining piles and direct foundation

A new type of hybrid foundation, which combines piles and a direct foundation to supplement their bearing capacity each other, has been proposed. The principle of this type of foundation is shown below. The foundation structure is composed of a few number of bearing piles and foundation slabs, as well as a pile head reaction control device connecting the bearing piles and the foundation slabs penetrating through them. When a load equal to or less than a given value is transferred to the bearing piles, causing a load more than a given upper limit to be applied, formation (sliding) is induced with the upper limit of load retained.

2. Pile head reaction control device In this example, this method was applied to a material storage (The construction was started in December 1999 and

finished in June 2000). The storage was a two-store reinforced concrete building, the span-wise elements were frame-worked and the ridge-wide elements were brace-worked. The plane size of the building was 15.0 m (span-wise) × 27.6m (ridge-wise), the height was approx. 10 m, the foundation was double-slab structured, and the self weight of the building was 30.5MN (with no load). When a standard pile foundation (pile: φ500 mm, t=12 mm, long-term bearing capacity 0.83MN) is used, approx. 40 piles are required. On the other hand, in this building, a hybrid foundation, which accepts a certain level of settlement, has been adopted and four piles were installed in the vicinity of the corners of the building, one sitting at each corner. The piles penetrate through the double-slab foundation base and the pile heads were connected to the foundation base through the pile head reaction control device in the same way as that in the previous section. Before the foundation base was cast, a 1 mm layer of rubber asphalt had been applied t the peripheries of the piles at the points where they penetrate through the foundation base.

1. Yutaka Fujita, Kiyoshi Ishii, Eiji Ogisako, Takaki Sakurai, Kazutaka Nakayama and Atsuo Onoue “Full-scale Testing of New Hybrid Foundation” Soils and Foundations, Vol.43, No.3, pp.11-22, 2003.6

2. Yutaka Fujita, Kiyoshi Ishii, Takaki Sakurai, Kazutaka Nakayama, Atsuo Onoue and Eiji Ogisako “Characteristics of Reaction Control Device for New Hybrid Foundation” Soils and Foundations, Vol.43, No.3, pp.23-31, 2003.6

3. Yutaka Fujita, Kiyoshi Ishii, Kazuhiko Yamazaki, Eiji Ogisaki, Takaki Sakurai and Kazutaka Nakayama “Characteristics of Reaction Control Device for New Hybrid Foundation” Journal of Technical and Design, Architectural Institute of Japan, Vol.17, pp.113-116, 2003.6

Data supplied by Shimizu Corp.

杭基礎 杭頭荷重制御機構を組み込んだ併用基礎

建物 建物

支持杭

軟弱地盤

支持杭 地盤反力

基礎スラブ

杭頭反力調整装置基礎スラブ直下の地盤の沈下による空間

支持層 杭の支持力

Pile foundation Combined foundation integrating pile head load controller

Gap left due to ground settlement directly under foundation slabs

Building Building Pile head repulsive force adjuster

Foundation slab

Soft ground

Bearing pile Bearing pile Ground repulsive force

Pile bearing force Bearing layer

6

4. Control Pile

Supplied by : Tsutomu Hirade

This method is useful in restoring from differential settlement or inclination due to ground settlement or in extending or reconstructing buildings because of modified usage. It involves 1) adding a pile to the existing one, 2) adding new piles, and 3) accommodating the piles inside the building to alleviate differential settlement or increase the bearing capacity. In the example of extending or reconstructing the building, new holes for piles penetrating through the foundation slabs, where control piles are added. The building load acts on the pile heads through the side frames of the control piles with the piles and slabs not connected. Between the pile bodies and ends, 1 m of precast piles are pressed in one by one for connecting them in many cases. These types of piles are difficult to be designed, though they are intended to maintain and manage the foundation and therefore, importance is put on past experiences and achievements.

Structural calculation for horizontal capacity has not been considered.

Building Research Institute conducts the IT test on control piles in collaboration with CENAPRE (Mexico city) and UNAM in Mexico city. 1) J. Mendoza: Foundation Engineering in Mexico City: Behavior of Foundation, Proceeding of the international symposium on geotechnical engineering of soft soils, SMMS,1987,351-367 2) M.Alcocer, RMendosa, J.Mendoza, L.Dominguez and T,Hirade: Possibility of Integrity test as Damage investigation method of pile Foundation in Mexico city. Survey Method of earthquake Disaster related with Buildings and Houses, Eqtap, B.R.I Report, March, 2001,pp85-90

Loading frame

Foundation slab

7

5. Foundation Works using Light-weight Materials (Direct Foundation)

Method: Columbus Method Light-weight resin form soil material is placed under or on the sides of the foundation to alleviate/prevent

differential settlement, reduce earthquake shock, insulate the foundation, and protect against frost damage. When the foundation is cast, it may be used as a framework. It has been used in more than 200 houses. It should be noted that some foam materials may tend to dissolve or swell when coming in contact with oil or solvent, or the like. In some cases where piles can not be used because of protection of ruin or leased land, as well as no effect of friction piles can not be expected, this method may be used. Building Engineering Examination Certification (The Building Center of Japan), NETIS of National Land and Transportation Ministry. Data supplied by: Nakamura Bussan

A=foundation load B=countermeasure against liquefaction C=pressure spring action D=building load control panel E=ground reaction F=light-weight soil (building bearing layer) G=load split control panel H=light-weight soil ground I=earthquake source J=underground water level K=protective wall, shock insulating material with space RC panel L=load P1 M=factory vibration N=load P2 O=subsurface layer (water) P=ground spring Q=sway control panel

Cause for differential sedimentation

Snow cover Covered snow load

Tripping moment calculation

Bias in building load Insufficient ground reaction Variation in ground reaction Variation in residual consolidated amount of sedimentation Liquefaction due to earthquake

Seismic movement

Building load

Resin form draining member

A

B C D E

F G H B

F G Q H

IJ

Environmental vibrations

K L

M N

Compression spring action

Resin foam draining member O

P

Wind pressure

Light weight soil

Resin form draining member

8

6. Long-short pile combined foundation design (design principle)

Method: Long-short pile combined technique In Shanghai, the intermediate layer sandwiched between soft soil layers lies in the ground structure. When short piles are used in the intermediate layer to support the entire foundation, the amount of settlement becomes far larger than as in long piles being used (Left: shot piles: 186mm, long piles: 71mm). In contrary, by combining long-short piles, the amount of settlement may be suppressed to the middle level between long and short pile levels, achieving higher economical efficiency.

Data supplied by: Pile Foundation Laboratory, Underground Construction Course, Tongji University, Changhi, China Prof. Yang Min, GS. Wang Wei, GS Yang Hua

地面

弱土软 层

(上 持力层 层)

弱土软 层

硬土 或基岩层

硬土层

(下 持力层 层)

Fig. 1 Soil distribution suitable for long-short pile foundation

图1 适于长短桩基础的土层分布示意图

地面

弱土软 层

(上 持力层 层)

弱土软 层

硬土 或基岩层

硬土层

(下 持力层 层)

Fig. 1 Soil distribution suitable for long-short pile foundation

图1 适于长短桩基础的土层分布示意图

短桩

长桩

浅 持力层 层

深 持力层 层

建筑物

图2 长短桩组合桩基础示意图

Fig.2 Sketch of long-short pile foundation

短桩

长桩

浅 持力层 层

深 持力层 层

建筑物

图2 长短桩组合桩基础示意图

Fig.2 Sketch of long-short pile foundation

mm

图3 全短桩基础布桩图

Fig.3 Location of short pile foundation

mm

图3 全短桩基础布桩图

Fig.3 Location of short pile foundation

0 1 2 3 4 5 6 7 8 9 10

X/m

0

1

2

3

4

5

6

7

8

9

10

Y/m

图4 全短桩基础沉降等值线图

Fig.4 Displacement contour of short pile foundation

0 1 2 3 4 5 6 7 8 9 10

X/m

0

1

2

3

4

5

6

7

8

9

10

Y/m

图4 全短桩基础沉降等值线图

Fig.4 Displacement contour of short pile foundation

mm图5 全长桩基础布桩图

Fig.5 Location of long pile foundation

mm图5 全长桩基础布桩图

Fig.5 Location of long pile foundation

0 1 2 3 4 5 6 7 8 9 10

X/m

0

1

2

3

4

5

6

7

8

9

10

Y/m

图6 全长桩基础沉降等值线图

Fig.6 Displacement contour of long pile foundation

0 1 2 3 4 5 6 7 8 9 10

X/m

0

1

2

3

4

5

6

7

8

9

10

Y/m

图6 全长桩基础沉降等值线图

Fig.6 Displacement contour of long pile foundation

mm

1

2

短桩长桩

图8 长短桩基础布桩图

Fig.8 Location of long-short pile foundation

mm

1

2

短桩长桩

图8 长短桩基础布桩图

Fig.8 Location of long-short pile foundation

0 1 2 3 4 5 6 7 8 9 10

X/m

0

1

2

3

4

5

6

7

8

9

10

Y/m

图9 长短桩基础沉降等值线图

Fig.9 Displacement contour of long-short pile foundation

0 1 2 3 4 5 6 7 8 9 10

X/m

0

1

2

3

4

5

6

7

8

9

10

Y/m

图9 长短桩基础沉降等值线图

Fig.9 Displacement contour of long-short pile foundation

长桩

短桩

图14 沉降计算区域划分示意图

Fig.9 Sketch map of settlement calculation

长桩

短桩

图14 沉降计算区域划分示意图

Fig.9 Sketch map of settlement calculation

全 短 桩 基 础

3 .4 3

3 .9 0

3 .9 1

1 5 4 .5 8

2 2 .7 1

5 5 .7 2

5 4 .2 7

2 0 .5 6

4 5 .3 2

3 8 .5 4

3 8 .4 8

1 8 6 .5 1

7 1 .4 6

9 8 .1 6

9 6 .6 6

全 长 桩 基 础

长 短 桩 基 础 1

长 短 桩 基 础 2

Δ 1 Δ 2 Δ 3 总 沉 降

1 1 .3 7全 短 桩 基 础

3 .4 3

3 .9 0

3 .9 1

1 5 4 .5 8

2 2 .7 1

5 5 .7 2

5 4 .2 7

2 0 .5 6

4 5 .3 2

3 8 .5 4

3 8 .4 8

1 8 6 .5 1

7 1 .4 6

9 8 .1 6

9 6 .6 6

全 长 桩 基 础

长 短 桩 基 础 1

长 短 桩 基 础 2

Δ 1 Δ 2 Δ 3 总 沉 降

1 1 .3 7

表 1 各 计 算 区 域 及 总 沉 降 结 算 结 果 (mm )

T a b le 1 R e su lt o f se tt le m e n t c a lc u la t io n

Ground

Soft soil layer

A

Hard soil layer or base rock (lower bearing layer) Shallow bearing layer

Building

BB

C C

Shallow bearing layer

6

A=hard soil layer (upper bearing layer) B=short pile C=long pile

Soft soil layer

1

Annex 4 – Bearing Capacity Evaluation Techniques 1. Vertical loading test (static) 2. Rapid loading test I 3. Rapid loading test II 4. Shock loading test 5. Static press fit method (Pile construction method)

2

1. Vertical loading test (static, reaction pile)

Vertical loading test (reaction pile) This method is the most basic technique for pile vertical loading test. When the reaction piles have approached approx. 2 to 3D (D: pile diameter) each other, they may affect each other. For more information on the test methods and the interpretation of the tests, see the standards defined by the Society of Geotechnology.

Photo by System Measurement

Loading device (5000kN class) Loading device (15000kN class)

Loading device (15000kN class) Loading device (50000kN class)

Loading device (50000kN class) Loading device (5000kN class)

3

2. Rapid loading test I

A steel spring is attached to the pile head and up to 200 kg of weight is dropped down on it to measure the settlement.

Reference Kubota, Kuwabara, Tamura, Inoue, & Abe: Stresses and strains in soil around model pile subjected to Quasi-static vertical loading, Journal of Structural and Construction Engineering No.551, Architectural Institute of Japan, p.75、2002

4

3. Rapid loading test II

Cushion material (any of various type of materials, such as rubber and urethan resin) is attached to the pile head and a weight is fakken on it to exert impact. An optical displacment gauge is used to measure the amount of settlement. Data supplied by System Measurement

ロードセル

杭頭補強キャップ

重錐架台

落下重錐の重量

下部チャック

転倒防止フレーム　H鋼　 250*250*5500　 4本使用

台座　1100*1100*400 1.25tf

クッションチェラスト

支柱 l=5500 φ 165.2

2,500

700

台座　φ 970*350 0.50tf

ﾚｯｶｰ重

φ 250

上部チャック

PC鋼棒(φ 36)

重錐架台　3.5tf

合計　15tf

50tf　ジャッキ　4台使用

重錐ブロック　5tf*2=10tf

重錐プレート 5tf*2=1.5tf

モンケン

クッション材

H

試験杭

GL

光学式変位計 OD-SYSTEM

光学式変位計ターゲット

杭体内歪ゲージ

加速度計

動歪ｱﾝﾌ゚ﾌ゙ ﾘｯｼ゙ ﾎ゙ ｯｸｽ ADｺﾝﾊ゙ ﾀー

ADｺﾝﾊ゙ ﾀー

ロードセル

Drop

Ham

mer

Strain gauge inside pile body

Accelerometer

C

Load cell

Cushion material

Optical displacement gauge target

Optical displacement gauge CD-SYSTEM

1 2 3 4 5 6 7 8

A

B C D E F G H I J

1) Upper chuck 2) PC steel rod (Φ36) 3) Lower chuck 4) Column support I=5500

Φ165.2 5) Weight frame 6) Cushion cellasto Φ250 7) Loading cell 8) Pile head reinforcing cap

A=wrecker weight B=mass weight of falling weight

C=weight block 5tf*2=10tf

D=weight plate 5tf*2=1.5tf

E=weight frame 3.5tf F=Total 15.tf

G=base 1100*1100*400 1.25tf F=base Φ970*350 0.50tf G=tip-resistant frame H steel 250*250*250 Four wires used H=four 50tf jacks used

Test pile

Bridge box Dynamic strain amp

AD Converter

5

4. Shock loading test

図１ 上昇波のマッチング解析例 鋼管杭、杭径Φ1,000mm 杭長 44, [(t9/2,000+t1 Fig. Example of matching between rising waves Steel pipe pile, diameter Φ1,000mm Pile length 44,500mm

[(t9/2,000+t12/9,500]+(t9/11,000+t9/11,000)+(t9/11,000)) Design bearing capacity 2.738MN Note) In the figure, a light blue line indicates the time required for one round trip by the wave

Dynamic impact is exerted on the pile head using a hydraulic hammer and the pile weight-displacement relationship is obtained to estimate the bearing capacity. This method has been used since 1995 and successfully applied to 220 cases.

Data Supplied by Geotop Corp.

0

1

2

3

4

5

0 10 20 30

変位量　S0(mm)

荷重　P0(M

N)

Fig.2 Pile head-displacement relationship Steel pipe pile, pile diameter Φ600mm

Pile length 4,500mm[(t12/3,000+t9/6,500)+(t9/10,000))] Design bearing capacity 1.400MN Note) Obtained by the weight transfer method.

-1

0

1

2

3

0 10 20 30 40 50

時間　(ms)

力　(M

N)

計測上昇波

計算上昇波

杭一往復の時間

加速度計

ひずみゲージ

ブ リ ッ ジ

ボックス

Time

力

Measured rising wave Calculated rising wave Pile round trip time

Wei

ght

Displace.

Accelerometer

Bridge box

Strain gauge

6

5. Static press fit method (PUSH piles, China, precast concrete piles)

Method: Static press fit pile The precast piles are pinched and pressed fit into the ground by static weight. The reaction force used for pressing piles is ensured by the weight of stacked steel sheets. For large buildings, PHC piles are mainly used, though square reinforced concrete piles (in some cases, cast-in-place piles) may be used. In Shanghai, for standard buildings, the length of pile used is 60 to 70ｍ and even for three-store buildings, 50 m of piles may be used in some cases. Even 40 to 50 cm length of φ600 piles are statistically pressed in the ground. In this statistic press fit method, it takes 20 to 30 minutes to completely press in the ground a 100t of 14 m rod for cottages (low-rising buildings) and a 400~500t of 14 m rod for 30-store buildings. Up to 900t class of machines are available. Since 7 to 8 yeas ago, this method has been used instead of cast in pile as part of vibration/noise countermeasure. In Shanghai, it is considered that this method can be more easily quality-controlled and has better quality and performance than those of cast-in-place piles. Vibration/noise may be lower than those of cast-in piles or buried piles in Japan. Protection has been attached to the pile top to prevent the pile body from being damaged when coming in contact with debris. In some cases, the piles have cross-shaped tops. The machine has a function enabling it to move as if it is an inchworm. To facilitate penetration into the ground surface, the ground where the piles are pressed in, may be excavated using an auger. When the piles are pressed in the ground, the ground shifts horizontally, causing damage to the structures in the surroundings. Accordingly, soil around the site may be discharged out to prevent the ground from deforming.

Cooperation: Shanghai 岩土工程勘察工程院有限公司 (Shanghai, China, 張富根理事長)

1

Annex 5– Earthquake-resistance Improvement Techniques (1) Pile head joint 1. Pile head joining device I 2. Pile head joining device II 3. Pile head joining device III 4. Pile head joining device IV 5. Pile head joining device V 6. Pile head joining device VI 7. Pile head joining device VII 8. Pile head joining device VII 9. Pile head joining device IV 10. Pile head joining device X 11. Pile head joining device XI 12. Pile head joining device XII (2) Pile bodies 1. Pile skin buffer material I 2. Pile skin buffer material II (3) Earthquake resistant techniques 1. Countermeasure against liquefaction 2. Detached house I 3. Detached house II (Vibration Instruments Inc.)

2

(1) Pile head joint

1. Pile head joining device I

Schematic drawing

(1) When pile head stress is low (pile head comes in contact） (2) When it is high (pile head rises)

Method: Cap ring pile technique Applicable piles: All types of piles including precast piles, cast-in-place piles, and steel pipe piles Materials: Steel, concrete, mortar, polyethylene foam sheets for isolating from unwanted concrete Construction: A precast concrete ring (PC ring), in which a steel sheet has been inserted, is attached on the pile head.

The PC ring is selected from the standard products for each type, diameter, and shear stress of the piles. Cement paste is filled into a gap left between the PC ring and the pile body.

Features: Easy construction, 0.7 to 0.8 of fixing capacity for short-term design, behaves as in a pin at terminal stage. Shear stress is carried by the PC ring.

Achievement：3116 piles were constructed at 54 sites (as of August 2004) Reference: Yoshimatsu, Miyata et al: Development of Semi-rigid joint between pile head and footing Parts 1-10，Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan，2001 to 2003

http://www.kajima.co.jp/news/press/200301/17a1fo-j.htm Data Supplied by Kajima Corp.

Pile

PC ring

Pile cap

Pile

PC ring

Pile cap

PC ring made in PC factory is being carried in the site.

→ Mortar applied

around the pile

↓

PC ring attached

Joining work finished ←

3

2. Pile head joining device II (Cast-in-place pile)

Method: Semi-hard pile joining technique (SOHP technique) The head of a cast-in-place pile or a cast-in-place steel pile concrete pile is taper-formed to reduce its area. An intermediate degree (between pin joining and fixed joining) of fixing is ensured between the pile and the foundation. The pile main reinforcing steel and steel pipes are fixed at the head and a joining reinforcing steel inserted into an area, of which cross section is reduced instead of being fixed to the foundation footing. By evaluating the effect of the extracted reinforcing steel by means of a rotary spring at the head, the hardness of the head can be assessed. General certification was granted by The Building Center of Japan. This technique was applied to the apartments in Aichi and Tottori.

Experimental Study on Semi-rigid Pile Head Connection for Cast-in-place Concrete Pile (Parts 1-3), Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan 2002 and 2003 Data Supplied by Konoike Corp.

Diameter

Min. diameter of taper of head

Main reinforcing steel

Joining reinforcing steel

Column Footing

Underground beam

Joining rein. steel Shear rein. steel

Unwanted concrete

Taper of head

Head of main reinforcing steel

B

Pile main rein. steel

B=Taper mold frame Lower hoop rein. steel

Upper hoop rein. steel

4

3. Pile head joining device III

Method: Head Pin technique (Super Pin technique) To reduce damages to the pile heads and foundations by an attach of earthquake, the pile heads are joined in a

manner similar to that of pin bearing by a joining device (super pin) shown above is installed between the foundation and the pile heads. Two members, the top cover and the ring seat come in contact with each other on the spherical plate and then rotate on it, minimizing a bending moment at the joining point. Compared with the conventional hard joining method, this method reduces the cross sections of the pile body and the foundation beam, as well as construction cost of the foundation. The top cover and the ring seat are made of ductile cast iron, which has higher strength and durability (Certification of designated building material was granted by the minister of land, infrastructure and transportation) and special surface finishing is not applied to them, achieving cost saving. There are two types; 4MN type for constant axial tension 400 tf and 8MN type for 800 tf.

In June 2004, in addition to cast-in-place piles, certification of general construction method, which is applicable to steel pipe piles, PHC piles, etc., was granted by The Building Center of Japan (BCJ certification：FD0050-02).

Data Supplied by Shimizu Corp.

Top cover (ductile cast iron)

Ring seat (ductile cast iron)

High-tension bolt

Protective cover Foundation beam

Anchor bolt O ring

Top cover

Ring seat Pile

Center of curvature

Anchor bolt

Spherical plate

5

4. Pile head joining device IV (precast pile)

Method: DYNACAP Rotary elastic spring joining (three spring types; vertical, horizontal, and rotary) General certification was granted as a pile head joining device by The Building Center of Japan. This method is applicable to all the precast concrete piles with a diameter less than φ1000.

The support has a single-layer (or multi-layer) rubber sandwiched, of which horizontal shear deformation (3 cm of clearance) is allowed. If the inclined angle of the head exceeds 1/100, it may be adjustedby a self-leveleing rod. Miyazaki & Nishimura: Swiveling pile head joining device—Adaptive to the secondary design, Kisoko, Vol. 12, 2001

Data Supplied by Dynamic Design & Asahi Kasei Corp.

写真６ ＤＹＮＡＣＡＰ設置状況（１分）

写真７ ＤＹＮＡＣＡＰ向き調整（１分）

写真８ ＤＹＮＡＣＡＰ設置後傾斜角確認写真９ ＤＹＮＡＣＡＰ設置状況 写真１０ ＤＹＮＡＣＡＰ周囲埋戻し完了

写真２ 工場出荷前の杭頭接合装置ＤＹＮＡＣＡＰ 写真３ 杭頭傾斜角測定状況（θ≦1/100rad）

写真４ 杭頭上面補修後の状況（θ＞1/100rad）Adjustment by a self-leveling bar.

図３ 杭頭接合装置ＤＹＮＡＣＡＰの断面構成図４ 杭頭接合装置ＤＹＮＡＣＡＰの力学モデル

Dynamic model of joining device Construction of joining device

Pile joining devices before shipment DYNACAP

Inclined angle of head being measured (θ ≤ 1/100rad)

DYNACAP being attached (1 minute) The orientation of DYNACAP being

adjusted (1 minute)

Inclined angle of attached DYNACAP being checked

DYNACAP attached DYNACAP buried back

Rotary spring

Vertical spring

Stopper

Clearance

Horizontal spring

Urethane form

Pile body

Middle connecting members

Lower connecting members

Stopper

stud bolt

Upper base plate Upper connecting members

Connecting steel plate

Connecting steel plate

Lower base plate

Auxiliary element

Connecting steel plate

6

5. Pile head joining device V (cast-in-place pile)

Method: BP-CAP (Ball point pile cap) Universal pile head joining technique for cast-in-place piles using rolling motion. Contact mechanism of two spherical surfaces with different curvature radii, reducing friction due to sliding induced by the same curvature. Horizontal movable distance between 凹 and 凸 members: 12 to 20 mm Clearance : Rolling deformation angle 1/10 to 1/16 (soft urethane form) General certification was granted as a pile head joining device by The Building Center of Japan.

Miyazaki, Nishimura, and Sugawara: Development of a Ball Point Joint for Cast-in-place Concrete Piles (Part 1), Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, September 2003 Data Supplied by Dynamic Design

Ｒ

ｒ

Ｒ －ｒ

Ｗ

杭 杭

（接触部機構）（マクロな概念） （実際の形状）

Ｂ Ｐ － Ｃ Ａ Ｐ の 原 理 説 明 図

上部 凸部材

発泡 材

クリアランス充 填材

コンクリー ト充填部

(軟質発 泡ウレタンなど )

(発泡 スチ レンなど )

吊下げ用 アイボル ト

アンカーボルト

下部凹部材

ＢＰ－ＣＡＰの断面構成図

Cross section of BP-CAP Explanatory drawing of BP-CAP principle Anchor

bolt

Hanging eye bolt

Form material (e.g., urethane

Clearance filler (e.g. soft urethane

form)

Lower member

Concrete filling portion

Upper member

Pile(Schematic view) (Contact mechanism) (Actual shape)

Pile

7

6．Pile head joining device VI (head joining/quake absorbing device)

Method: BSL(Ball Point Slider) Sliding bearing with rolling mechanism for cast-in-place piles, spherical surface contact rolling mechanism ＋ sliding mechanism is serially aligned. Rolling mechanism (凹 and 凸 spherical surfaces), sliding plates (fluorine-coated stainless steel), sliding plates (polyamide resin), 凹 and 凸 spherical surface material (ductile cast iron), Either of pile head joining device or quake absorbing device may be used. Performance certification as a quake absorbing device and general certification as a pile head joining device were granted by The Building Center of Japan.

Miyazaki, Nishimura, & Sugawara: Development of a Ball Point Joint for Cast-in-place Concrete Piles (Part 5), Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, September 2003

Data Supplied by Dynamic Design & Asahi Kasei Corp.

上部凸部材

下部凹部材

上部すべり板

クリアランス充填材

コンクリート充填部

(軟質発泡ウレタンなど) 発泡材

アンカーボルト

ＢＳＬの断面構成図

Ｗ

杭

（変形時の状態）

Ｒ

ｒ

（実際の形状）

基礎フ ーチング 水平力

（基本構成）

回転機構

すべり機構Ｗ

杭

（変形時の状態）

Ｒ

ｒ

（実際の形状）

基礎フ ーチング 水平力

（基本構成）

回転機構

すべり機構

ＢＳＬの原理説明図

コンクリート スタッドボルト

すべり受材裏板

すべり板

コンクリート

上すべり

柱頭に使用 柱脚に使用

上すべり

杭頭に使用

下すべり

スライダー

Cross section of BSL Explanatory drawing of BSL principle

Upper sliding plate Anchor bolt Upper 凸 member

Form material

Clearance filling material(soft urethane form)

Lower 凹 member

Concrete fill. portion

Foundation foot. Hor. force

Rolling mechanismPile

Actual shape Original Deformed

U. slidingPile head

L. sliding

Concrete

U. sliding

Pier stud Pile head

D

Slider

Concrete

Sliding mechanism

stud bolt

8

7. Pile head joining device VII (precast pile)

Method: PSL （Pre-cast pile slider） Sliding bearing with rolling mechanism for precast piles, spherical surface contact rolling mechanism＋sliding

mechanism are serially aligned. Rolling mechanism (凹 and 凸 spherical surfaces), sliding plates (fluorine-coated stainless steel plates)

Sliding material (polyamide resin), 凹 and 凸 spherical material (ductile cast iron) Data Supplied by Dynamic Design & Asahi Kasei Corp.

既製杭用回転機構付すべり支承

PSL

既製杭

すべり板の塩水噴霧試験結果

材質：SS400表面処理：なし

材質：SS400表面処理：溶融亜鉛メッキ

試験前

２４時間後

試験前

５０００時間後

材質：SUS304表面処理：フッ素コーティング

試験前

１０００時間後

Sliding bearing with rolling mechanism for precast piles

Result of saltwater spraying test on sliding plates

Material:SS400 Surface finishing: none

Material:SS400 Surface finishing: hot dip zincing

Material:SUS304

Surface finishing:

fluorine coated

before before before

Precast pile

24 hours after 1000 hours after

5000 hours after

9

8. Pile head joining device VIII （cast-in-place）

Method: Rubber Sheet Universal Rolling Pile Head Joining Universal pile head joining for cast-in-place piles. The vertical load is carried by means of bearing stress of the rubber body. Rolling hardness may be adjusted by declined rubber body. The foundation footing and the pile body are fixed by a shear key. Shear stress is carried by the shear key.

Miyazaki, Saiki, & Oowa: Practical Research for Seismic Upgrading of Piles (Part 1), Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, 1999 Data Supplied by Dynamic Design

Footing

High-power mortar Rubber

body

Pile body Shear key

10

9. Pile head joining device IX (small-diameter steel pipe pile)

Method: BP-CAP (small-diameter steel pipe pile) Data Supplied by Dynamic Design

11

10. Pile head joining device X

Method: Pile head structure allowing its rising (stepping structure) Construction: A reinforcing steel pier is inserted into a steel box base to ensure pile head’s upper and lower motion. Seismic control: Compared with fixed pile head, 20 to 30% of shock may be reduced. Examples: The entire pile risen (8-store reinforcing steel framed building, CFT column), The partial pile risen (7-store reinforcing steel framed building) Data Supplied by TAKENAKA CORP.

8650 7100 86507100

31500

地震力

地震波：BCJレベル２

7

6

5

4

3

2

1

階

20x10-3 1050

層間変形角 Ry(rad)

固定モデル 浮き上がりモデル

マットスラブ

差込み鉄骨

箱状ベース

場所打ちRC杭

浮き上がり部

立体フレームCG

マットスラブ

差込み鉄骨

箱状ベース

場所打ちRC杭

マットスラブ

差込み鉄骨

箱状ベース

場所打ちRC杭

浮き上がり部浮き上がり部

立体フレームCG

Rising portions

3D frame CG

Mat slab

Inserted reinforcing steel

Box base Cast-in-place RC pile

Fixed model Rising model

Seismic shock

Store

Angle of deformation between layers RY (rad) Seismic wave: BCJ level 2

12

11. Pile head joining device Ⅺ

Method: P/R piling Clarified joined pile head state, Alleviated damage to pile heads by an attack of earthquake, reduced cross sectional area of the upper element, applicable to a wide variety of pile types and diameters, streamlined design of pile foundation. General certification (BCJ certification-FD0013) was granted by The Building Center of Japan in March 2001. Additional certification (BCJ certification-FD0013-02) was granted for improved method. Data Supplied by Yasui Architectural & Design Corp.

Sealing

RA-type bearing (sliding bearing) RA-type bearing (hermetically closed rubber bearing)

Anchor steel

Upper shoe

Dust seal

Sliding member

Lower shoe

Packing

Crushed stone

Elastomer

Lower shoe

Base plate

Crushed stone

Upper shoe

Ground

Ground

Precast concrete pile (also applicable to cast-in-place concrete piles)

Sealing

13

12. Pile head joining device (energy absorption considered) XII

Method: Stud with lead dumper

Reinforcing steel for joining the foundation slab is stud-welded on the end steel plate anchoring the PC steel member. Lead used in quake absorbing devices is attached around the stud reinforcing steel to ensure time-history effects of lead elastic deformation involved with the reinforcing steel motion.

To ensure reductions in response of the building and pile stress at an attack of earthquake, seismic energy is absorbed (namely, reduced) at the pile junction by means of building locking and pile head rolling.

Energy may be absorbed by means of shear deformation of lead involved with reinforcing steel motion inside the lead member. Almost all the energy absorbed by the lead member is consumed as heat.

Experimental Study on Pile Head Joint for Energy Absorbing Method (Parts 1-5), Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, 2000 & 2001 Data Supplied by Tsutomu Hirade, Building Research Institute

① ②

鉛ダンパ付き スタッド鉄筋

基礎スラブ

PHC 杭

(負)(正)

試験体No.2(軸力980kN)

-300

-200

-100

0

100

200

300

-80 -60 -40 -20 0 20 40 60 80変位(mm)

荷重(kN)

杭体(軸力980kN時）の設計破壊曲げモーメント（Mu）レベル

反力壁 250

フレーム

950

1750 2700

1250

正加力方向

Stud reinforcing steel with lead dumper

After the experiment

Side of pile end plate being welded

スチールパイプ（鉛外周部）

加力方向

歪みｹﾞｰｼﾞ

歪みｹﾞｰｼﾞ

Horizontal load and displaced loading point

Frame

Positivepower-applying direction

Stud reinforcing steel with lead dumper

Foundation slab

PHC pile

positive negative

Reaction w

all

Load (kN)

Test piece Nb.2 (axial force 980kN)

Displacement (mm)

Rubber cap

Force applied

End plate

Lead wire

Strain gauge

Welded Steel pipe (lead around it)

pile (under axial force 980kN) design breaking bending moment (Mu) level

Lead Lead wire

Strain gauge aluminum pipe (Φ32)

Schematic view of force applying

TC

14

(2) Pile bodies

1. Pile periphery buffer materials I

Pile periphery buffer materials (buffer materials, which are not destroyed under ground pressure in uneventful state, but compressed and deformed by an attack of earthquake) ・ Precast pile: sponge-like soft resin board ・ Cast-in-place concrete pile: Styrofoam molded board (with surface protective layer） Name of construction method: DYNASOFT method Protection of a pile body from the forced deformation caused by foundation displacement Attachment of soft buffer material layer (pile cover) around the pile body

Data Supplied by Dynamic Design Co., Ltd

写真１ 杭中間部の応力低減工法＝ＤＹＮＡＳＯＦＴ工法の施工状況Example of application to a precast pile

Example of application to a cast-in-place concrete pile

15

2. Pile periphery buffer materials II

Name of the construction method: Columbus pile construction method To minimize and protect against adverse effects of earthquake shock, a lightweight resin foam soil supplement is attached around the outer ground. Some applications to minimize traffic vibrations have been reported. Above photos show the application to the cast-in-place concrete pile. Exemplified by the foamed polypropylene material, which acts as a buffer in occurrence of ground deformation by an earthquake. The performance requirements include resistance to plastic deformation by ground vibrations and durability. Reference: Vibration characteristics of foundation structure using lightweight resin foam soil supplement， Takuzo Nakamura, The investigation committee for new technologies on the prediction of environmental vibrations and the countermeasures against them, Proceeding, The Japanese Geotechnical Society, Data Supplied by Nakamura Bussan Inc.

16

(3) Earthquake resistant techniques

1. Countermeasures in case of liquefaction

The construction method: Combined TOFT and Piled Raft Foundation

Name of the construction Method: TOFT method, Combined TOFT and Piled Raft Foundation method To reduce and protect against liquefaction, any layer possibly liquefied is grid improvement members. The effectiveness of this method in protecting against liquefaction has been also confirmed even in the event of Hanshin Earthquake Disaster. The conventional Piled Raft Foundation (PRF) is a technique, by which two bearing elements of building load are used: 1) direct foundation and 2) piles. On the other hand, Combined TOFT and PRF add one more bearing element to PRF: grid improvement members. It have a number of advantages such as achievement of a minimized number of piles and a miniaturized pile diameter at a time, as well as reduced construction period and environment-friendliness. Received The 4th National Land Engineering Development award and “The 4th National Land Engineering Development award” in 2002 Data Supplied by Takenaka Corporation

液状化の恐れがある層

固い地盤

建物全重量

直接基礎

TOFT杭

液状化の恐れがある層

固い地盤

建物全重量

直接基礎

TOFT杭

Total building weight

Direct foundation

Pile

Firm ground

Possibly liquefiable layer

17

2. A detached house (The seismic isolator using sliding bearings and Pca continuous footing)

Method: The seismic isolator using sliding bearings and buffer materials for Pca continuous footings. This isolator has double layer Pca continuous footing; a fluoropolymer-coated steel plate is sandwiched between

two bases as a sliding bearing. The buffer materials placed on both sides of reverse T-shaped continuous footing suppress its sliding.

Reference Iiba and Tamura et al: Introduction of Slip Base Isolation System for Houses and the Results of Shaking Table Test, Soil and foundation, No.45,1999

Buffer materials

(Foaming materials) Fluoropolymer -coated steel bearing

(Outside) A shed (inside)

Pca continuous footing

(Outside)

Fig. 1 Floor plan of Pca base-isolated foundation

Cross section of a test body Plane of a test body Fig. 3 Section view of Pca base-isolated foundation Fig. 2 Plan view of Pca base-isolated foundation

Sliding bearing: at 29 points

Fluoropolymer-coated steel plate: 45 cm square Fuuoropolymer-coated steel plate: φ10 cm Buffer material: at 36 points Repulsive wall

Repulsive wall

Excitation direction

3000

Excitation direction

Buffer materials

Fluoropolymer-coated steel plate: φ10 cm 175 175

A B C D E F

Fluoropolymer-coated steel plate: 45 cm square

Continuous footing Continuous footing

Weight: approx. 6tf

Pca continuous footing approx. 3tf

Buffer material Base

Excitation station

18

3. A detached house II

Applicable structures: Small-size buildings such as detached houses (The houses adopting a vibration damping system), Structure: The vibration damping foundation composed of a sliding bearing, a damper and, upper and lower parts of foundation concrete, Features: No restoration mechanism integrated and ordinary structural calculation is used. Restoration: To restore a displaced house back to its original position after an earthquake, hydraulic jacks are inserted into pre-formed openings under floor.

Data Supplied by VIBRATIONIN INSTRUMENTS CO., LTD.

Continuous footing

Damper

Raft foundation Vibration damper unit

Vibration damping unit absorbs earthquake energy

Drastically damped vibration

B

D

C A

B

D

A: Vibration damper unit B: Continuous footing C: Damper D: Raft foundation

A C

Earthquake vibaration Depending on the magnitude of an earthquake

some displacement may occurs.

1

Annex 6 – Evaluation of Foundation Defects

To evaluate any damages and defects of the foundation, the indications for qualitatively determining various types of events in the foundation are required. Almost no study on this issue has been conducted. In this material are described the principle of defects which may occur in the foundation defined in Housing Quality Assurance Law.

“Law concerning the promotion of housing quality assurance” (hereinafter, simply referred to as the law), which is applicable only to dwelling houses (detached and apartment houses) rather than all kinds of buildings, was established in 2001 and stipulates the referential measure for the guarantee period against defects and the house performance certification mark system 3),4).

According to the referential measure, the definition of the old guarantee period against defects by the civil law was revised to 10 years for main components, which are important from the aspects of structure and durability including foundations and piles and foundations. The old guarantee period for defects defined by the civil law was 5 years for wooden houses and 10 years for reinforced concrete houses. On the other hand, a contract has precedence under the legal system and in almost all the cases, the guarantee period has been determined under the agreed contract. In this context, the period might be about one year in many cases. It should be noted that the law defines the defects and other problems mentioned above and thereby, it is necessary that not only the presence/absence but also of defects is quantitatively discussed. Accordingly, in accordance with the provision under Article 70 of the law, Notification No. 1665 announces the criteria for determining the possible defects.

Among the criteria defined in the Notification mentioned above, one criterion, which is related to the performance of foundations, is used to determining cracks and defects of the foundations. Any differential settlement and inclination of houses seriously affect the functions of houses. On the other hand, the evaluation is not applied to any inclination of the foundation alone. The inclination of the foundation will be discussed together with those of floors and columns. In the notification mentioned above, the conditions of the structure to be evaluated are ranked into three levels; 1) low possibility (level 1) 2) mediate possibility (level 2), and 3) high possibility (level 3). At level 3, the foundation has; 1) 0.5 mm or more wide cracks its concrete structure and 2) 20 cm or more deep defects (Figures 2 and 3). For differential settlement of the foundation, at level 3, the floors or columns have inclined at an angle of 6/1000 or more. To evaluate the inclination of floors, measurement shall be made over an interval of 2 m or more, avoiding any effect of the interval. Figures 1 show the examples of the levels of possible cracks of the foundation and their actual states. The criteria for determining the possibility of defects in accordance with the performance mark certification are applicable only to the houses, for which inspections and verifications were made and the building performance certification described later was given. These criteria are not applicable to other kinds of houses and standard buildings, as well as those, which were attached by a natural disaster in rare cases, although practically, they are used in evaluating the integrity of standard buildings in many cases. It should be noted that the criteria are applicable only to newly constructed houses and the evaluation system for the existing houses has been established according to that for the newly constructed houses.

2

傾斜角θ

ひび割れ幅Ｗ 建設住宅性能評価書の交付住宅

表 床の傾斜に対する瑕疵の存在する可能性 住宅の種類

レベル 木造住宅、鉄骨造住宅、鉄筋コンクリート造住宅又は鉄骨鉄筋

コンクリート造住宅

構造耐力上主要な部分に

瑕疵が存在する可能性

1

3/1000 未満の勾配の傾斜 凹凸の少ない仕上げによる床の表面における２点（３ｍ程度以上離れて

いるものに限る）の間を結ぶ直線の水平面に対する角度をいう。

低い

2 3/1000 以上 6/1000 未満の勾配の傾斜 一定程度存する 3 6/1000 以上の勾配の傾斜 高い

注：建設住宅性能評価書が交付された住宅を対象とした場合。

表 基礎のひび割れに対する瑕疵の存在する可能性（湿式の仕上げ材の場合） 住宅の種類

構造耐力上主要な部分に瑕

疵が存在する可能性

レベル 木造住宅、鉄骨造住宅、鉄筋コンクリート造住宅又は鉄骨鉄筋

コンクリート造住宅

1

レベル 2 及びレベル 3 に該当しないひび割れ

低い

2 仕上材と構造材にまたがった幅 0.3mm 以上 0.5mm 未満のひ

び割れ（レベル 3 に該当するものを除く） 一定程度存する

3

①仕上材と乾式の下地材にまたがったひび割れ ②仕上材と構造材にまたがった幅 0.5mm 以上のひび割れ ③さび汁を伴うひび割れ

高い

注：建設住宅性能評価書が交付された住宅を対象とした場合。

図-16 住宅品質確保法における瑕疵の可能性を判断する目安の例

Fig. 1 Example of an indicator for determining any possible defects defined in the law “Descriptions of Technical Standards to be Considered in Housing Dispute Settlement

Procedure”, Center for Housing Renovation Dispute Settlement Support, 2000

Defect

House with built house performance certificate given

Table Possibility of defects involved with inclined floor

House type Level

Wooden, reinforced, reinforced concrete, or steel framed reinforced houses

Possibility of defects in main components from the aspect of durability

1 Inclination at an angle of less than 3/1000 An angle of a straight line connecting two points (3 m or more apart from each other) on floor surface with less undulation relative to horizontal level

Low

2 Inclination at an angle of more than 3/1000 and less than 6/1000 Moderate

3 Inclination at an angle of 6/1000 or more High

Note: The houses with the built house performance certificate certification given were evaluated

Table Possible defects due to inclined floor

House type Level

Wooden, reinforced, reinforced concrete, or steel framed reinforced houses

Possibility of defects in main components from the aspect of durability

1 Cracks not ranked in levels 2 and 3 Low

2 More than 0.3 mm and less than 0.5 mm in width cracks across finishing and structural members

Moderate

3 1) cracks across finishing and dried substrate members 2) 0.5 or more in width cracks across finishing and structural members 3) Cracks with rust dripping

High

Note: The houses with the built house performance certificate certification given were evaluated

Inclined angle θ

Crack width W

3m or more

Inclination

3

Fig. 2 (a) Examples of cracks in foundation classified into level 3 “Descriptions of Technical Standards to be Considered in Housing Dispute Settlement Procedure”, Center for Housing Renovation Dispute Settlement Support, 2000

Example of crack with width ≥0.5mm across wet finishing material and structural materialExternal wall finishing

Underfloor ventilating opening 0.5mm or more in width

Foundation finishing (mortar: wet material)

0.5mm or more in width

Structural member (base)

Structural member (footing foundation)

Damp-proof concrete

Examples of cracks classified in level 3 Example of crack across wet finishing material and dry base material

External wall finishing

Underfloor ventilating opening

Foundation finishing (mortar: wet material)

Base material (adiabatic board: dry material)

Structural member (base)

Structural member (footing foundation)

Damp-proof concrete

Example of crack with rust drip

External wall finishing

Cracks with rust drip

Structural member (base)

Damp-proof concrete

Structural member (footing foundation)

Underfloor ventilating opening

Cracks with rust drip

Foundation finishing (mortar: wet material)

4

Fig. 2 (b) Examples of cracks in foundation classified in level 2

Fig. 2(c) Examples of cracks classified in level 1 “Descriptions of Technical Standards to be Considered in Housing Dispute Settlement Procedure”, Center for Housing Renovation Dispute Settlement Support, 2000

Example of crack with width ≥3mm, 0.5mm> across wet finishing material and structural material

External wall finishing

Structural member (base)

Structural member (footing foundation)

Foundation finishing (mortar: wet material)

0.5mm> width ≥0.3mm

Underfloor ventilating opening

0.5mm> width ≥0.3mm

Damp-proof concrete

Example of crack with width <0.3mm across finishing material and structural material

External wall finishing

Structural member (base)

Structural member (footing foundation)

Foundation finishing (mortar: wet material)

0.3mm> width

Underfloor ventilating opening

0.3mm> width

Damp-proof concrete

Example of crack classified in level 1 Example of crack only in finishing material

External wall finishing

Structural member (base)

Structural member (footing foundation)

Foundation finishing (mortar: wet material)

0.5mm or more in width.

Underfloor ventilating opening

Damp-proof concrete

5

Fig. 3(a) Examples of defects in foundation classified in level 3 “Descriptions of Technical Standards to be Considered in Housing Dispute Settlement Procedure”, Center for Housing Renovation Dispute Settlement Support, 2000

Examples of cracks classified in level 3 Defect across wet finishing material and dry base material

External wall finishing

Structural member (base)

Base material (adiabatic board: dry material)

Foundation finishing (mortar: wet material)

Underfloor ventilating opening

Damp-proof concrete

Example of defect with depth ≥20mm External wall finishing

Structural member (base)

Structural member (footing foundation)

Defect with depth ≥20mm

Foundation finishing: exposed concrete (structural material)

Underfloor ventilating opening Damp-proof concrete

Example of defect with rust drip

Damp-proof concrete

External wall finishing

Structural member (base)

Underfloor ventilating opening With rust drip

Defect with depth <5mm

Foundation finishing: exposed concrete (structural material) Structural member (footing

foundation)

6

Fig. 3(b) Examples of defects in foundation classified in level 1 “Descriptions of Technical Standards to be Considered in Housing Dispute Settlement Procedure”, Center for Housing Renovation Dispute Settlement Support, 2000

Defect with depth <5mm

Examples of defects classified in level 2 Example of defect with depth ≥5mm, 20mm> in structural material

External wall finishing

Examples of defects classified in level 1 Example of defect with depth <5mm in structural material

Damp-proof concrete

Structural member (base)

Underfloor ventilating opening

Defect with depth ≥ 5mm, < 20mm Foundation finishing: exposed concrete (structural material)

Structural member (footing foundation)

External wall finishing

Defect with depth <5mm

Structural member (base)

Structural member (footing foundation)

Damp-proof concrete

Underfloor ventilating opening

Defect with depth <5mm

Foundation finishing (mortar: wet material)

External wall finishing

Structural member (base)

Damp-proof concrete Foundation finishing: exposed concrete (structural material)

Underfloor ventilating opening

Examples of defects classified in level 1 Example of defect with depth ≥5mm, 20mm> in structural

t i l

Structural member (footing foundation)

7

This law stipulates the Japanese housing performance certification mark system, which requires that the certification marks to be acquired for not only the technical standards for defects and problems described above but also fire-proof and facility performances including structural performance. Adherence to this system is at the discretion of the constructors. It requires that when piles are used, diameters and lengths of the piles to be indicated. There are two types of performance evaluation; 1) design performance evaluation only at the design stage and 2) construction performance evaluation including field investigations at the construction stage. In each case, the mark may be indicated shown in Fig. 4.

For moderate earthquakes, it is defined the system, in which housing performance against three levels of shear stress (standard shear stress coefficients Co=0.2, 0.25, and, 0,30) is ranked at three levels (lowest standard (Co=0.2) is class 1, Co＝0.25 and 0.30 are class 2 and class 3, as defined in Construction Standard Law) in earthquake-resistance performance evaluation. The performance evaluation is made on the entire structure for ranking and thereby, in such a case where the upper structure is ranked class 3 and the foundation is ranked class 1, the result of evaluation on the entire structure becomes class 1.

For large earthquakes, however, only the structure on the ground is evaluated and its structural safety is ranked (Co=1.0 is class 1, Co＝1.25 and 1.50 are class 2 and class 3). In this case, no underground structure including the foundation is evaluated and in some cases, the structure on the ground has enough structural safety to be ranked Co=1.5, however, the underground structure satisfies only the moderate-earthquake standard but not the large-earthquake standard (Co=0.2, short-term allowable stress). The relationship between earth surface acceleration and Co used in considering liquefaction and the criteria for determining liquefaction have not been established by the law. Accordingly, basically, liquefaction must be evaluated by the allowable stress calculation based on Co=0.2 defined by the law and it is at the discretion of the designer whether any other measure is taken.

This means that the evaluation system of building foundation earthquake-resistance performance, in which in addition to the evaluation in the general primary design stage (Co＝0.2), the evaluation is more strongly focused on the standard shear

Fig. 4 Marks given to the performance certification under the housing performance certification mark system

Left: Construction performance evaluation including field investigation, Right: Design performance evaluation only at the design stage

8

stress for the moderate earthquake than that stress-resistance calculation in examining the foundation state for large earthquakes (Co=1.0), has been clearly established by the law.

The law also stipulates that as part of the housing performance certification mark system, the documents and materials necessary for performance evaluation shall be kept. Generally, they always need not to be kept, however, the law stipulate that the documents and materials necessary for performance evaluation shall be kept by the designated performance evaluation bodies for 20 (construction performance evaluation) or 10 years (design performance evaluation) as shown in Fig. 4. To accurately conduct integrity evaluation of buildings, earthquake-resistance diagnosis, and earthquake-resistance reinforcement works, it is important that design documents are kept. On other words, the provisions defined in the law are useful.