PDA PIT Method's Statement IG 000 M 1000 0801 YA

NARUČITELJ / CLIENT:

REPUBLIC OF KOSOVO MINISTRY OF TRANSPORT AND COMMUNICATIONS PROJEKT / PROJECT:

MORINË TO MERDARE KOSOVO MOTORWAY PROJECT DIONICA / SECTION:

Sections 1, 2 and 3

METHOD'S STATEMENT

1. DYNAMIC PILE LOAD TEST

2. PILE INTEGRITY TEST

PROJEKTANT TEMELJENJA / FOUNDATION DESIGNER:

KREŠIMIR BOLANČA, M.Sc. (Civ.Eng.) VODITELJ ISPITIVANJA / TESTING MANAGER: OLINKA MIRKOVIĆ, B.Sc. (Physics Eng.)

DATUM / DATE: Srpanj / July 2010

OZNAKA DOKUMENTA / FILE CODE:

IG – 000 – M – 1000 – 0801 – YA REVISION YA

KONZULTANT / CONSULTANT:

INSTITUT IGH 10 000 ZAGREB, J. RAKUŠE 1

File Code: IG – 000 – M – 1000 – 0801 - YA INSTITUT IGH d.d.

Type: METHOD'S STATEMENT GEOTECHNICAL DEPARTMENT

Zagreb, Janka Rakuše 1

KOSOVO MOTORWAY PROJECT, SECTION 1, 2 and 3 PDA and PIT REPORT

methods statement.doc Page 2 of 6

1. DYNAMIC PILE LOAD TEST

The dynamic pile load test is based on measuring strain and pile acceleration caused by a

drop hammer with the minimum weight of 1.5% of the tested pile bearing capacity

(according to Rausche et el). The right structure for lifting and releasing the weight should

be used (Figure 1.).

Sensors are attached to the test pile for measuring deformation and acceleration. The

sensors are placed axially and symmetrically on 4 sides of the pile, approximately 1.2 m

below the pile head, as shown in Figure 2. The weight drop causes a compressive wave

which travels down the pile towards foundation, then causes a reflection, which then

travels back up the pile. The sensors detect a wave and transfer data onto the so-called

PDA device (Pile Driving Analyser), so that for each weight drop the change of force

(derived from the measured yield) and yield velocity (derived from the measured

acceleration) are displayed on the screen at the measuring location and in terms of time.

Based on strain measurements and the known modulus of elasticity of the pile concrete,

the dynamic forces in the pile are computed, whereas velocities are derived at by

integrating the accelerations.

Figure 1. Weight drop system used for testing Picture 2. Sensors attached to the pile, connected

to PDA device

All the data is saved onto the computer hard drive, so they may be analysed in detail after

the test is completed. The measuring method and procedure are covered under the ASTM






D4945-89 standard, and specified under the recommendation for dynamic pile tests of

Technical Committee 5 of the German Geotechnical Society.

Upon carrying out the dynamic load testing, the obtained analogue data on force and yield

are digitalised for computer analysis on a PC by way of the CAPWAP Programme (Case Pile

Wave Analysis Programme), with wave equation as its basis. The pile and soil model is

presented with one of the measured curves, whereas iteration (the change of pile and soil

model) is used to find the best fit between the measured and computed curves. Once a

satisfactory overlap of curves is achieved, the soil model properties become known as does

the ultimate bearing capacity of the tested pile. By gradual load of the model obtained in

this manner (computer simulation of the static pile load test), we also get a graphic

presentation of the force-yield for the tested pile.

The final result of these tests is the static pile bearing capacity established by way of a

method known as case method. This method has been developed by D.D. Goble and F.

Rausche during the late 1960’s and early 1970’s, and by the early 1980’s it was adopted

around the world as a valuable tool in engineering practice.

If the test is done according to standards the ratio between pile capacity from static and

dynamic load test is in 15% range (according to Bengt H. Fellenius).

The most important results of these tests are:

- static pile bearing capacity estimate

- determination of maximum dynamic compressive and tensile stress in a pile under

impact

- establishment of pile’s continuity

- determination of all the performances of the hammer-pile-soil system (for driven

piles)

THE EQUIPMENT FOR DYNAMIC PILE LOAD TESTING

12 ton weight drop system, with free fall height up to 3 m, will be used for dynamic pile

load test (Picture 1.). Pile Driving Analyzer (PDA, Picture 2.) acquires data from

acceleration and strain sensors attached to the pile, and processes these signals as the pile

is impacted by a drop weight.






Figure 3. Example of dynamic load test results

PREPARATION OF PILES

All the piles to be tested have to be properly prepared, ie. reinforced concrete follower

with the same diameter as the pile, and length of ≈ 2 m, should be produced on clean pile

head. Reinforcement cage is shown on drawing 3. The test can be carried out when all the

concrete (pile and the follower) is at least 14 days old.

- The top of the concrete follower has to be smooth and horizontal

- There has to be at least 1 m of free space all around the pile

- The pit around the pile has to be dry (with no groundwater)

- To unload, montage and lift the weight, suitable crane should be available on site.

Crane capacity should be at least 50t, depending also on distance between the

crane and the pile

- The ground on the site has to be prepared for the crane, please keep in mind that

the whole weight drop system weights 20 t, and has to be transported an unloaded

as close to the pile as possible (5 – 7 m)






2. PILE INTEGRITY TEST (PIT)

The design proposes integrity testing of all piles by the PIT method (Pile Integrity Test).

The integrity testing is carried out once a pile head is driven to the design elevation. This

testing is used to prove that the piles have all been driven in continuation, without voids in

concrete, and that there are no zones of lower quality or reduced diameter compared to

the designed pile dimensions.

PIT performs the wave equation-based non-destructive test known as Pulse or Sonic Echo

Test, or Low Strain Dynamic Test. The test consists of attaching one accelerometer to the

foundation, and using a small hand-held hammer to impact it. The PIT displays curves that

reveal any significant changes in cross section that may exist along the shaft.

Preliminary data on all implemented tests should be promptly delivered during

performance. After the testing is completed, a detailed analyses and reading of the results

should be submitted in the form of a final report. The Low Strain Dynamic Testing method

employed by the PIT complies with ASTM D5882-07.

In case damage is established, as well as voids in concrete of more significant proportions,

the piles will be remediated. This remediation may be carried out by drilling boreholes

through the piles and by grouting under pressure with an appropriate grout mixture.

Prepared by: Krešimir Bolanča, M.Sc. (Civ.Eng.) Olinka Mirković, B.Sc. (Physics Eng.)






Prepared by: INSTITUT IGH d.d. GEOTECHNICAL DEPARTMENT

Project: MORINË TO MERDERE MOTORWAY

Assignment:

PRELIMINARY GEOTECHNICAL DESIGN FOR MORINË TO MERDARE MOTORWAY SECTION 1 BRIDGE3

Type: GEOTECHNICAL DESIGN

3. FOLLOWER REINFORCEMENT

Place and date: Zagreb, July 2010

Documents

PDA PIT Method's Statement IG 000 M 1000 0801 YA