[CCH] BST22316 2012_2013 Sem B RW Assignment

7/28/2019 [CCH] BST22316 2012_2013 Sem B RW Assignment

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Semester B, 2012/2013

BST 22316

Construction Technology

Lecturer:

Mr. WONG Wai Man Raymond

Individual Assignment

Student Name: Cheung Chun Hin

Student I.D.: 52999911

Hand-in date: April 2, 2013


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Table of Content

1. Introductions / Assumptions / Overall View2. Stage 1 - Ground Stabilization Provisions3. Stage 2 - Cut-off Walling Provisions/Lateral Soil4. Support Provisions5. Stage 3 - Excavation Arrangement6. Stage 4 - Dewatering Arrangement7. Stage 5 - Spoil Removal Arrangement8. Stage 6 - Basement Construction Arrangement9. Conclusion10.References


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1.Introductions / Assumptions / Overall View1.1 Abstract

In building a deep and large-size basement, there are various elements and

considerations such as labor, space, material, machineries, basement design

requirement, etc. As for a successful project, a proper arrangement and control

is important, therefore we will focus on situation analysis, make appropriate

approach and problem solving methods in the each of the following parts.

In this report, there will be mainly focus on the basement construction with the

6-7 principle steps. By illustration of diagram and photos taken by me, it would

be explained in detail about the actual steps of construction sites and material

types. More than learning in text book through theories, it is learning in a more

realistic method and manner.


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Nature & Purposes

Project Aims: This project is to build up a building with a deep and large basement

1.2 Master Flow Chat

1.3 Common managerial problems identified in the construction of deep basement:1. Very expensive and time consuming in nature, often involved

huge amount of work resources.

2. Inconsistent and sensitive to the quality of planning and

management of individual projects.

3. Works are highly hazardous, both to human operatives

working within and the life and properties of third parties that

within the vicinity.

4. Works involved a lot of managerial challenges. Such as, in

the preparation of a highly efficient working programme,

monitoring and rectifying the progress of works in case

problems arising, or in resources planning where materials,

labours & plant equipment are involved.


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2.Stage 1 - Ground Stabilization Provisions2.1 Purpose

There are mainly 3 functions for ground stabilization, including strengthens

improvement (increase load-bearing capacity of soil), dust control (alleviate

dust generated by machinery operations), and soil waterproofing (to increase

waterproofing ability of soil from surface)

2.2 Situation AnalysisGiven that the site is large in size and the soil in weaker in nature, the main

function for ground stabilization is to strengthen soil load bearing capacity so

that the soil have sufficient stability to support the loading from the building(dead-load) and users (live load).

2.3 Possible Methods & ChoiceThe method of soil stabilization is broadly divided into 2 approaches, chemical

soil stabilization and mechanical soil stabilization. In Hong Kong, there is

mainly using grouting which is under chemical soil stabilization approach

1. Add quicklime / hydrated limeMechanism: absorb the water / moisture in soil

Advantages: easy transportation, cheap

Considerations: cannot reach deep underground, time-consuming


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2. Fly ashMechanism: reduce the air voids

Advantages: easy transportation, cheap

Considerations: cannot reach deep underground, time-consuming

3. GroutingMechanism: reduce the air voids, control water fillings, prevent sand

deification, reduce vibration, and reduce settlement.

Advantages: numerous varieties of functions, stable, effective

Considerations: comparatively expensive

Recommendation

Among the above options, it is recommended to take grouting as the way to

stabilize the ground, because it is relatively efficient, reliably stable.


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2.4 SequenceCement grout is formed by mixing water, cement, sand in a proper ratio (typical

proportion by weight is 1:0.5:3). It is intended that cement mortar is

constructed by placing, packing, or pressure pouring. Owing to the relatively

high water content, the mixing of cement with water produces a fluid

suspension which can be poured under base plates or into holes. Then to wait

some days for setting and hardening, this process is to create a good

performance. After the grouting is finished, a substantial proportion of load is

designed to be transferred by the bedding to other members.

2.5 Considerations of this Method2.5.1 Rainy weather may lengthen the time-requirement for setting, weaken or

even damage the grouting.2.5.2 Strong sunlight may damage the grouting quality2.5.3 It is necessary to control the voids in the soil, because excessive voids may

affect the strength, stiffness and permeability of grout

2.6 Solutions2.6.1 Ensure the soil quality by civil engineer2.6.2 Prepare the project time properly in avoid construction within rainy seasons.Calculate the mixture ratio of grouting carefully based on the soil data, and add other

chemicals whenever necessary.


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3.Stage 2 - Cut-off Walling Provisions/Lateral SoilSupport Provisions

3.1 PurposeTo withstand the lateral loading of the site, so that the site can be safe when

constructing basement or other works.

3.2 Situation AnalysisWe assumed that the soil is bad graded and soil content is wet in nature. There

are adjacent buildings nearby. We should consider the spacing and the sufficient

support to the side force.

3.3 Possible Methods & ChoiceThere are many ways to construct a cut-off wall. Despite of the methods are so

many, there are commonly 6 types of practices in Hong Kong which are as

follow:

1. Steel pile

[Photo taken ME @ 1/4/2013 Wu Hu Street]

Advantages: resist tension

Considerations: rusting may occur

STEEL PILE

Lateral Support


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2. Soldier pile

[Drawn by Me]

Advantages: reusable, reliable, relatively cheaper than steel pile

Considerations: rusting may occur, require accuracy jointing

3. Hand-dug caisson

Advantages: cheaper cost

Considerations: very dangerous to workers life


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4. Bore pile

Advantages: very stable

Considerations: expensive, permanent

5. Mini-pile or pipe pile

Advantages: suitable for small or medium construction site

Considerations: rusting may occur, limited to 12m depth

6. Diaphragm wall

Advantages: fully supported

Considerations: require more complex procedure and more support system


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Recommendation

After the choosing the above choices, it is better to use diaphragm wall with

steel struts and diagonal bracing in this situation (but not using anchor),

because it support deep excavation without using other underground

spacing.

Elevation:

[Photo taken by ME@1/4/2013 Intercontinental Hong Kong expansion work]

Illustration Drawings [Drawn by Me]:

Section:


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NOT USING ANCHOR (because buildings nearby)

[Photo taken ME @ 1/4/2013 Chatham Road North]

3.4 Case Example

Just like the basement work in Intercontinental Hong Kong expansion work

Anchors

Increase the slope stability


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() which owned by the New World Development

Company Limited. The basement used the diaphragm wall with lateral

supported by the steel struts and diagonal bracing. It is a common and

economic method which broadly adopted in large site construction.

3.5 Considerations of this Method1. Require more complex procedure2. Need more spacing3. Preparations require more time

3.6 Solutions1. Recruit more skilled labor2. Carefully planning the site spacing and use more


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4.Stage 3 - Excavation Arrangement4.1 Purpose

Before building a new structure at a specific site, excavation of the original spoil

above or below the ground is needed so that the building works are process

properly. There are several considering factors which are as follow:

1. Nature of subsoil affect type of machine used and the necessity of soilprotection.

2. Size of excavation affect type of machine used and method to excavate.3. Scale of work large volume of excavation may involve complicated phasing

arrangement and work planning

4. Ground water condition affect degree of protection (watertight sheetpiling or dewatering may require)

5. Surrounding condition impose certain restrictions and precautions (e.g.diversion of a government drain, or underpinning work to the nearby

building foundation)

6. Depth of excavation affect use of spacing and working platform4.2 Situation Analysis

In this site, the subsoil is loosely compacted, not much rock and there isnecessary to strengthen the soil. Since the site is large enough, large machines

with higher efficiency are available in use. In building a deep basement,

excavation machines are needed to work at the bottom of the designated site

with different level at each of the time. So, when the basement is not deep,

there would only need to use simple excavation machines; but when it is deep

enough, it would necessary to use machines support long distance carrying.


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4.3 RecommendationIt is recommended to take excavation in a way ofbencharrangement for open

site. Firstly, it excavate the central part of soil and make it similar to open-cut

method. Then it forms slopes at the surroundings and excavate the soil at the

side after the central part is clear. This is a pattern that the site would be

excavating into a shape like bench when we looking at the top of the site. This

has an advantage that the remaining soil can act as a support at the corners

while there is sufficient spacing provided for operation of work. About the edge

of the remaining soil, it would be good enough to have cut edge with step or

edge of cut, because these 2 shapes are safety enough. Even there is a heavy

rain, it would not easily collapse or slide down.


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5.Stage 4 - Dewatering Arrangement5.1 Purpose

It is a process to remove the over-saturated water in ground and keep the

subsoil within a non-saturated condition.

5.2 Situation AnalysisWe assume that there is no underground river crossing the expected working

space, high water table and there is a need of dewatering. In this case, we are

going to build a deep and large size basement, therefore we should dewatering

as a way to lower pore pressure in soil and avoid causing any damages by base

heave.

5.3 Possible Methods & ChoiceIn total there are 3 methods in dewatering, including:

[Active drainage method]

Dewateringby deep wells

Dewatering by wellpoints &

[Passive drainage method]

Dewatering by horizontal drainage.

1. Dewatering by deep wells

Advantages: drain large amount of water at a time

Disadvantages: uneven drainage over the whole construction site


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2. Dewatering by wellpoints

Advantages: very flexible arrangement, occupied less area

Disadvantages: not as efficient as the above method

3. Dewatering by horizontal drainage (e.g. sump pit)

Advantages: no need to exclusively excavate

Disadvantages: working condition is poorer, passive

Recommendation

After analysis the above methods, we will choose to take dewatering method

by well points. Because the site condition is assumed to have no underground

river which no need to drain large amount of water, but needed to drain evenly

over the whole site. Whenever necessary, we should also use dewatering by

horizontal drainage.

5.4 Precautions5.4.1 It has to be ensure the depth, number, distribution of wellpoints are

appropriate

5.4.2 The use of horizontal drainage should be ready when site level reached theoriginal water table level


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6.Stage 5 - Spoil Removal Arrangement6.1 Purpose

There are always spoils created by excavation, ground displacement work,

in-suit materials, etc. In order to protect the adjacent environment and to cope

with the regulations, it is necessary to remove the spoils in a proper method. In

addition, there are some special materials requires special treatment before

discharge (e.g. Asbestos). Therefore, it is undoubtedly that even removal

requires a plan.

6.2 Situation AnalysisIn the construction of a basement, there would probably have the followingspoils:

1. Soil2. Concrete materials3. Sewage4. Temporary non-reusable structures5. DustBut in the above, we will focus on soil removal arrangement. Because soil takes

the largest portion of spoil in nearly every site. When in considering soil removalmethod, we would make decision on using what types of excavator and why to

use them.

6.3 Possible Methods & ChoiceThere are many types of excavator, including:

1. Compact excavator [Photos taken by ME @1/4/2013 Chatham Road North]

Advantages: higher mobility

Disadvantages: lower weight can be carried (0.7-0.8 tones)


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2. Dragline excavator [Photo taken by ME@1/4/2013 Intercontinental Hong Kong expansion work]

Advantages: Able to transport 168 meters and 450 tones material

Disadvantages: extremely high capital cost

3. Long reach excavator

Advantages: support distance away carriage

Disadvantages: (same with Compact excavator)

4. Steam shovel


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Advantages: allow to install on the train

Disadvantages: Uncommon to be use

5. Power shovel

Advantages: very powerful in harrying weight

Disadvantages: not applicable in all types of construction

Recommendation

From the analysis of the above excavators, we decided that Compact excavator

and Dragline excavator will be used in the construction work. There will be

around 10 compact excavator working at the basement site and cooperativelywork with dragline excavator at the upper level of the site.

6.4 Considerations of this Method6.4.1 Accidents maybe happen during lifting the soil upwards6.4.2 Spacing is important for accessing6.4.3 Air pollution is serious in the site6.4.4 Air pollution and noise pollution may affects the surroundings6.5 Solutions6.5.1 All workers should equipped with safety protective equipment and supervise

by experienced manager

6.5.2 Keep area tidy6.5.3 Improve air ventilation of te site6.5.4 Cover the working site area with plastic curtain


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7.Stage 6 - Basement Construction Arrangement7.1 Purpose

Illustrate basement construction method within the common choice of

Open-cut arrangement, Bottom-up arrangement, Top-up arrangement

with considerations of efficiency and economy.

7.2 Situation AnalysisAs information given, the proposed basement site is large in size and deep.

Therefore 4 points can be deduced as follows:

1. Numerous large machineries are supported to work at the same time2. The lateral support is heavy3. Basement works working time requirement proportionally larger than

normal site, as in accounting the whole project time requirement

4. The basement can support complex construction environment5. System formwork may be used if the spacing can appropriately handled

7.3 Possible Methods & ChoiceConsidering using which of the methods in basement construction, factors like

construction environment, machineries, spacing and spoiling removal methodsare important and the following table shows the major comparison with each of

the methods.

Open- Cut

Top-down Bottom-up

Size of site Very large Large Medium to small

Site environment Unobstructed Adaptable to most

environment

Adaptable to most

complex environment

Lateral Protection Minimum Limited shoring

support

Complex lateral

support

Machineries

Support

All size

machinery

Only small size

machinery

All size machinery

Space provision Not much Not much Temporary vertical

support is needed

Spoil removal

method

Most Limited Limited, but more

choice


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Recommendation

After comparing 3 common practices in Hong Kong, it is affirmative that

Top-down method is the most appropriate one among the choices. The

reasons are as follow:

1. Support above ground construction carried out simultaneously2. Save the cost of formwork3. Settlement can be reduced4. Less time requirement

[Drawn by ME]

7.4

Considerations of this Method1. Accurate cost analysis or work study is difficult to carry out for there is

limited commonality to make comparisons.

2. A great number of random and uncontrollable variances are likely to ariseduring the courses of work. This makes planning and scheduling almost

cannot be exact.

3. The actual effectiveness of works is highly depended on the as-constructedsite environments.

4. Quality of the management and the executing parties, as well as theproblems solving ability of the frontline personnel, also seriously affects the

performance and effectiveness of works.

7.5 Problem Solutions1. Collecting the material data from the market and make use of bulk purchase

when prices are low, properly manage use of material and avoid wastage.

2. Make thoughtful building plan before the start of work3. Keep area tidy by place unnecessary equipment away the working area4. Recruit skilled managers and workers


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8.Conclusion

After the above 6-7 involvement principle, we can conclude that theconsiderations are broadly classified as cost, materials, working method, time, design,

structural properties and management. It is the utmost consideration of construction

in Hong Kong that, time and conveniences are more an essential factors in the whole

working process because the income on sales or rental of the building is a large

amount of pays, compared to the cost of constructing it.

Another point is that, compared to the past years, safety concerns are arising its

importance to any of the constructions in Hong Kong. In the past, building basement

is a difficult and dangerous job as accidents may frequently appeared, particularly

the cut-off method called Hand-dug Caisson1. This kind of method is extremely

dangerous as anything dropped into the hole almost killed the man as there are no

where he can escape. Therefore, I have check online and discovered that, it has been

strictly discourage and even prohibited to be applied in Hong Kong, unless it is

proved that no other way to construct without using this method and have a

convincing evidence about the safety in applying this method.

1Refer to Reference No. 6


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9.ReferencesWEB SITE

1. Basement Construction in Bottom-Up Methodhttp://deltacorp.vn/index.php?option=com_content&view=article&id=191&Itemi

d=340&lang=en

2. Construction of basement in Top-Down methodhttp://deltacorp.vn/index.php?option=com_content&view=article&id=192%3Ata

ng-ham-theo-phuong-phap-top-down&catid=72%3Acong-ngh-mi-ang-ap-dng&Ite

mid=339&lang=en

3. Essential Health and Safe Tips in Basement Constructionhttp://www.hse.gov.uk/pubns/cis66.pdf

4. Goodwood Residence Basement Construction Sequence by Steve R. Nebreshttp://www.authorstream.com/Presentation/stevenebres-598273-basement-con

struction-sequence/

5. Deep Underground Basements for Major Urban Building Constructionhttp://www.nicholsonconstruction.com/techresources/techPapers/PDF/Deep%2

0Underground%20Basements%20Final%20with%20edits%20-%2010-14-03.pdf

6. Hand-dug Caissonhttp://www.safetypartnering.com/smd/inside_c4_c.htm

7. Introduction to Soil Stabilizationhttp://china.cat.com/cda/files/408341/7/Soil%2520Stabilization%2520QEDQ122

9.pdf

BOOK

1. Puller, M., (1996), Deep Excavations: A Practical Manual, London: Thomas TelfordLtd.
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[CCH] BST22316 2012_2013 Sem B RW Assignment