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PPSSZZ 1199::1166 ((PPiinndd.. 11//9977))

UUNNIIVVEERRSSIITTII TTEEKKNNOOLLOOGGII MMAALLAAYYSSIIAA

BORANG PENGESAHAN STATUS TESIS***

JUDUL :ANALYSIS OF ELASTIC SETTLEMENT OF PETRONAS TWIN

TOWERS

SESI PENGAJIAN : 2005/2006

Saya _ MOHD RASDAN BIN ABDUL RAHIM _(HURUF BESAR)

mengaku membenarkan tesis *(PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan

Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut :

1. Tesis adalah hak milik Universiti Teknologi Malaysia.2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan pengajian

sahaja.3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran di antara institusi

pengajian tinggi.4. ** Sila tandakan ( )

SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentinganMalaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI1972)

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan olehorganisasi/badan di mana penyelidikan dijalankan)

TIDAKTERHAD

Disahkan oleh,

(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)

Alamat : LOT 1480 TAMAN SRI DEMIT,

16150 KUBANG KERIAN,

KOTA BHARU, KELANTAN

Nama Penyelia : PN FAUZIAH KASIM

Tarikh : 28 APRIL 2006 Tarikh : 28 APRIL 2006

CATATAN : * Potong yang tidak berkenaan.

** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihakberkuasa/ organisasi berkenaan dengan menyatakan sekali tempoh tesis iniperlu dikelaskan sebagai SULIT atau TERHAD.

*** Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjanasecara penyelidikan, atas disertasi bagi pengajian secara kerja kursus danpenyelidikan, atau Laporan Projek Sarjana Muda (PSM).

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I hereby declare that I have read this thesis and in my opinion this thesis is

sufficient is terms of scope and quality for the award of the Bachelor of Civil

Engineering *

Signature : ______________________

Name of supervisor : FAUZIAH KASIM______

Date : 28 APRIL, 2006

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ANALYSIS OF ELASTIC SETTLEMENT OF PETRONAS TWIN TOWERS

MOHD RASDAN BIN ABDUL RAHIM

This project report is submitted as a partial requirement for the award

of the Bachelor Degree of Civil Engineering

Faculty of Civil Engineering

Universiti Teknologi Malaysia

APRIL, 2006

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ANALISIS ENAPAN ELASTIK BAGI MENARA BERKEMBAR PETRONAS

MOHD RASDAN BIN ABDUL RAHIM

Laporan projek ini dikemukakan sebagai memenuhi sebahagian daripada

syarat penganugerahan Ijazah Sarjana Muda

Kejuruteraan Awam

Fakulti Kejuruteraan Awam

Universiti Teknologi Malaysia

APRIL, 2006

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ii

I declare that this thesis entitled Analysis of Elastic Settlement of Petronas Twin

Towers is result of my own research except as cited in the references. The thesis has

not been accepted for any degree and is not currently submitted in candidature of any

other degree.

Signature : _________________________________

Name : MOHD RASDAN BIN ABDUL RAHIM

Date : 28 APRIL, 2006

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iii

To my beloved family, friends and UTM lecturers

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iv

ACKNOWLEDGMENT

I am really grateful to all parties whom had given me encouragement, help

and permission to collect all the data and the details for this study directly or

indirectly. Thank you to Pn Fauziah Kasim, a lecturer of Universiti Teknologi

Malaysia, Skudai who was my supervisor for giving me a lot of help and guidance in

my study. Also to Ir Mohd Bin Jamal from KLCC Holdings Berhad who helped me

in lending the data needed and the related information for this study. Lastly I want to

express my sincere appreciation to my family for giving me a moral support and

strength toward me in achieving a success in this course.

MOHD RASDAN BIN ABDUL RAHIM

APRIL 2006

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v

ABSTRACT

The Petronas Twin Tower is 450 m tall and supported by pile raft system.

The type of foundation used is to minimize the differential settlement. It is aninteresting fact that the friction piles varying in depth from 40 m to 105 m below the

ground level. An approximate approach has been performed for the analysis of

elastic settlement for KLCC twin towers. Both elastic settlements of pile and of soil

have been determined using basic theory of elastic settlement of piles and Janbu

immediate settlement approach. The soil parameters were approximated from the site

investigation report and the soil profile below the tower. The result from the study

case proved that the total settlement value for the towers is 91.8 mm which was

within the tolerable value. Based on the soil profile and the soil properties,

consolidation settlement was not the major settlement effect to the structure.

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vi

ABSTRAK

Menara Berkembar Petronas (KLCC) adalah setinggi 450 m dan di galas oleh

gabungan sistem asas cerucuk dan asas rakit. Jenis asas yang digunakan adalah

bertujuan untuk mengurangkan enapan perbezaan. Satu informasi yang menarik bagi

sistem asas yang digunakan kerana ianya terdiri daripada cerucuk gesel yang ditanam

sedalam 40 m hinggalah 105 meter. Satu kaedah anggaran telah dibuat untuk

menganalisa enapan anjal untuk menara berkembar KLCC. Kedua-dua enapan anjal

iaitu enapan anjal oleh cerucuk dan enapan anjal oleh tanah telah di tentukan

menggunakan teori asas enapan anjal untuk cerucuk dan teori enapan serta merta

oleh Janbu. Parameter untuk setiap lapisan tanah ditentukan terlebih dahulu

berpandukan daripada laporan kajian tanah dan setelah itu bentuk latar belakang

tanah ditentukan. Keputusan daripada kajian kes membuktikan bahawa jumlah

enapan bagi menara adalah 91.8 mm, iaitu berada dalam julat yang dibenarkan.

Berpandukan kepada bentuk latar belakang tanah dan parameter tanah, enapan

pengukuhan bukanlah enapan utama yang memberi kesan kepada menara tersebut.

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vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

LIST OF CONTENT vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xii

LIST OF APPENDICES xiv

CHAPTER 1 INTRODUCTION

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Objectives of Study 3

1.4 Scope of Study 3

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viii

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 4

2.2 Consolidation Settlement 5

2.2.1 Total Consolidation Settlement 6

2.3 One Dimensional Consolidation Theory of

Terzaghi

8

2.4 Example of Structure Settlement 9

CHAPTER 3 METHODOLOGY

3.1 Introduction 14

3.2 Data Collection 15

3.3 Background of the Case Study 16

3.3.1 Geological condition 18

3.4 Elastic Settlement of Soil 19

3.5 Elastic Settlement of Pile 21

CHAPTER 4 ANALYSIS AND RESULTS

4.1 Introduction 27

4.2 Parameters 27

4.3 Soil Profile 29

4.3.1 Calculation for elastic settlement of soil 32

4.3.2 Calculation for elastic settlement of pile 33

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ix

CHAPTER 5 CONCLUSION

5.1 Introduction 35

5.2 Conclusions 36

5.3 Recommendations For Future Study 36

REFERENCES 38

Appendices A - C 40 - 74

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x

LIST OF TABLES

TABLE NO TITLE PAGE

2.1 Maximum allowable settlements of some structures

(Sower, 1962)

13

3.1 Elastic parameters of Various Soils (Das, 1999) 24

3.2 Typical Values of Cp (Das, 1999) 25

4.1 Liquid limit from Lot C borehole 30

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xi

LIST OF FIGURES

FIGURE NO TITLE PAGE

2.1 Westend 1 cross-section and finite element mesh of the

system

9 & 10

2.2 Messeturm cross-section (Reul and Randolph, 2003) 11

2.3 Torhaus Der Messe cross-section (Reul and Randolph,

2003)

12

3.1 Methodology for the study 15

3.2 KLCC Foundation Profile (Hamdan, 1994) 17

3.3 Layout Plan for Barrette Pile (Hamdan, 1994) 17

3.4 Kuala Lumpur geological schematic (Ooi, 1986) 18

3.5 Based Rock around Kuala Lumpur (Ooi, 1986) 19

3.6 a Correction factor for finite thickness of elastic soil layer

(Das, 1999)

20

3.6 b Correction factor for depth of embedment of footing, Df

(Das, 1999)

21

3.7 Types of unit friction resistance distribution along the

pile shaft (Das, 1999)

23

3.8 Values of, av and r 24

4.1 Soil Profile of the site 30

4.2 Schematic of foundation and soil profile for KLCC

towers

32

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xii

LIST OF SYMBOLS

Ap - area of pile cross section

B - width of rectangular loaded area of diameter of circular loaded area.

cv - coefficient of consolidation

cp - an empirical coefficient

Cc - compression index

D - width or diameter of pile

Ep - Youngs modulus of the pile material

Es - Youngs modulus of soil

eo - the initial void ratio

Gs - specific gravity of the soil

Ho - the initial height of the compressible layer

Iwp - influence factor for determination of s2.

Iws - influence factor for determination of s3

L - embedded length of pile

LL - liquid limit

m - number of layers above the depth on interestp - perimeter of the pile

Qwp - load carried at the pile point under working load condition

Qws - load carried by frictional (skin) resistance under working load

condition

Qwp - point load per unit area at the pile point

qp - ultimate point resistance of the pile

qo - load per unit area.

S - total settlement

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xiii

Si - immediate settlement

Sc - the consolidation settlement

Ss - secondary compression settlement.

s - total pile settlement

s1 - settlement of pile shaft (shortening)

s2 - settlement of pile caused by the load at the pile point

s3 - settlement of pile caused by the load transmitted along the pile shaft

Sr compressible soil layer

t - time

ue - excess pore water pressure

y - depth of consolidating layer

zj - thickness of thejth layer

- magnitude depends on nature unit skin friction

e - change in void ratio

v - vertical total stress

'vo - initial vertical effective stress

'vf - final vertical effective stress

j - unit weight of thejth layer

1 - correction factor for finite thickness of elastic soil layer

0 - correction factor for depth of embedment of footing, Df

s - Poissons ratio of soil

sat - saturated unit weight

w - unit weight of soil

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xiv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Summary of Borehole Test Results 40

B Strain Gauge Instrumentation Record 51

C Lot C Site Investigation Location Plan 73

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CHAPTER 1

INTRODUCTION

1.1Introduction

The construction of tall buildings or high rise structure is a big challenge in

construction industry.Building is a structure designed for commercial, industrial and

residential proposes. Tall Building is a building in which tallness strongly influence

planning, design and use or a buildings whose heights create different condition and use

than those that exist use in common buildings of a certain region and period (Abdul,

2004).

Tall buildings have a sensitive characteristic in settlement especially differential

settlement. The high of structure increase the differential in buildings characteristic. So

the design of foundation for tall buildings has to fulfill the settlement, geotechnical

capacity for piles, structural capacity for piles and the construction is without any

technical problem (Ooi, 1986).

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Foundation is the most important structure of a building. It is a part of the

structures that have a direct contact with the ground and transmits the load of the

structure to the ground. There are several types of foundations that are shallow

foundations and deep foundations. Shallow foundations include strip foundations, pad

foundations and raft foundations. Deep foundations include piles, piles walls, diaphragm

walls and caissons.

1.2Problem Statement

Settlement analysis is important before and after the construction especially for

super structure. Before the construction begin, prediction analysis of settlement is

important in choosing the right foundation to be used and also the correct design for it.

After the completion of the structure, the analysis used to evaluate the damage of the

buildings due to consolidation settlement. The damage cause by the consolidation

settlement can be classified based from architecture, function and structure. If the

settlement was over the limitation, it will risk the civil life and also can damage other

structures surrounding it. The settlement of the building would react to the settlement of

the soil, and as a result, many problems would arise. Some possibilities are cracked

foundations and cracked columns that support the weight of the building. The building

could also lean to one side as is the case in the Tower of Pisa. An extreme case of leaning

to one side could cause the building to topple over. All of these effects would not be

beneficial to the stability of the building. As an example, a case reported in 1980 in Pulau

Pinang, a 16-storey apartment building demolished after the structure settled over its limit

during the construction period.

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3

1.3 Objective of Study

The main purpose of the study was to determine the settlement behavior of the

Petronas Twin Towers at Kuala Lumpur City Centre (KLCC). Therefore the specific

objectives of the study were as follows:-

1. To determine elastic settlement of individual pile2. To determine elastic settlement of soil due to the loading of the KLCC

twin towers.

1.4Scope of Study

The studies only focus in elastic settlement of pile and elastic settlement of soil.

Analysis for consolidation settlement was neglected because it was not a major effect to

the towers.

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CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

In 1920, the consolidation for clay investigated by Terzaghi. Terzaghi One

Dimensional Theory used widely in settlement analysis and characteristic. During and

after construction, surface loads from structure are transmitted to the soil profile. Stresses

increase within the soil mass and the structure undergoes a time-dependent vertical

settlement. The total settlement, S is calculated as the sum of the following three

components of settlement that is:

S = Si + Sc + Ss (2.1)

where Si is the immediate settlement, Sc is the consolidation settlement and Ss is the

secondary compression settlement. Immediate settlement is the time-independent

component of total settlement that occurs at constant volume as the load is applied to the

soil. Consolidation settlement is the time-dependent component of total settlement that

results from the dissipation of excess pore pressure from within the soil mass. Secondary

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5

compression settlement results from time-dependent rearrangement of soil particles under

constant effective stress conditions.

2.2 Consolidation Settlement

Consolidation settlement occurs as the result of volumetric compression within

the soil. For granular soils, the consolidation process is sufficiently rapid that

consolidation settlement is generally included with immediate settlement. Cohesive soils

have a much lower hydraulic conductivity, and, as a result, consolidation requires a far

longer time to complete. In this case, consolidation settlement is calculated separately

from immediate settlement.

When a load is applied to the ground surface, there is a tendency for volumetric

compression of the underlying soils. For saturated materials, an increase in pore water

pressure occurs immediately upon load application. Consolidation is then the process by

which there is a reduction in volume due to the expulsion of water from the pores of the

soil. The dissipation of excess pore water pressure is accompanied by an increase in

effective stress and volumetric strain. Analysis of the resulting settlement simplified if it

is assumed that such strain is one-dimensional, occurring only in the vertical direction.

The consolidation settlement of a cohesive soil stratum is generally calculated in two

steps:

1. Calculate the total consolidation settlement, Sc, or corresponding to thecompletion of the consolidation process.

2. Using the theory of one-dimensional consolidation, calculate the fraction of Scthat will have occurred by the end of the service life of the structure.

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In actuality, the total amount of consolidation settlement and the rate at which this

settlement occurs is a coupled problem in which neither quantity can be calculated

independently from the other. However, in geotechnical engineering practice, total

consolidation settlement and rate of consolidation are almost always computed

independently for lack of widely accepted procedures to solve the coupled problem.

The formula for Terzaghi one dimensional settlement is,

2dy

duc

dt

du ev

e = (2.2)

where, ue = excess pore water pressure

t = time

cv = coefficient of consolidation

y = depth of consolidating layer

2.2.1 Total Consolidation Settlement

Total one-dimensional consolidation settlement, Sc, results from a change in void ratio,

e, over the depth of the consolidating layer. The basic equation for calculating the total

consolidation settlement of a single compressible layer is

o

oc

e

eHS

+

=

1(2.3)

where eois the initial void ratio andHo is the initial height of the compressible layer.

Consolidation settlement is sometimes calculated usingHofor the entire consolidatingstratum and stress conditions acting at the sidelight. This procedure will underestimate

the actual settlement, and the error will increase with the thickness of the clay. As e

generally varies with depth, settlement calculations can be improved by dividing the

consolidating stratum into n sub layers for purposes of analysis.

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o

on

i

ce

eHS

+

=

= 11(2.4)

where ei, is the change in void ratio,Hoiis the initial thickness, and eoiis the initial void

ratio of the ith sub layer.

The appropriate ei for each sub layer within the compressible soil must now be

determined. To begin, both the initial vertical effective stress, 'vo, and the final vertical

effective stress (after excess pore pressures have fully dissipated), 'vf, are needed. The

distribution of'vowith depth is usually obtained by subtracting the in situpore pressure

from the vertical total stress, v. Vertical total stress at a given depth is calculated using

the following equation

(2.5)j

m

j

jv z=

=1

where

j = unit weight of thejth layer

zj = thickness of thejth layer

m = number of layers above the depth on interest

The final vertical effective stress is equal to the initial vertical effective stress plus the

change of vertical effective stress 'v due to loading:

vvovf ''' += (2.6)

For truly one-dimensional loading conditions, such as a wide fill, 'vis constant

with depth and equal to the change in total stress applied at the surface of the soil stratum.

For situations in which the load is applied over a limited surface area, such as a spread

footing, 'vwill decrease with depth as the surface load is transmitted to increasingly

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2.4 Example of Structure Settlement

Several case that happen to small buildings is like at Shin-Ube power plant, where

Chugoku Electric Co was built in 1956. Takaneka (1956) reported that the settlement

amount measured was 1.46 m. The soil profile for this site was clay and silt. There were

also several cases for settlement of tower recorded in Germany. For an example, Westend

1, Frankfurt, built from 1990 to 1993. The height of this tower building is 208 m and with

60 m high section of complex. The bottom of the Frankfurt clay is assumed to be 68 m

below the foundation level, which lies 145 m below the ground level. From the testing

conducted by Frakie and Lutz (1994) which used the finite element analysis, after 2 years

of the tower completion the measured settlement is 109 mm.

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Figure 2.1: Westend 1 cross-section and finite element mesh of the system (Frakie and

Lutz, 1994)

The second example is Messeturm tower that was build in 1988 and was

completed in 1991.In the vicinity of the Messeturm the subsoil consists of fill and

quaternary sand and gravel up to a depth of 10 m below ground level, which is followed

by the Frankfurt clay up to a depth of at least 70 m below ground level.The calculated

settlement at the centre of the raft amounted to 174 mm, whereas the last documented

measurement (December1998) gave a value of 144 mm.

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Figure 2.2: Messeturm cross-section (Reul and Randolph, 2003)

The third example for settlement analysis for tall building is the Torhaus Der

Messe. It was constructed between 1983 and 1986. The 130 m high Torhaus was the first

building in Germany with a foundation designed as a piled raft. A total number of 84

bored piles with a length of 20 m and a diameter of 09 m are located under two 17:5 m3

24:5 m large rafts. The distance between the two rafts is 10 m. As the building has no

under-ground storey, the bottom of the 25 m thick raft lies just 3 m below ground level.

The maximum load is equal to 200 MN for each raft (Sommer, 1991) minus the weight of

the raft is successively applied by means of a uniform load over the whole raft area. The

weight of one raft amounts to 26.8 MN and is applied over the whole area of the raft

before the stiffness of the raft. From the last documented settlement measurement in 1988

(Sommer, 1991) an average centre settlement for the two rafts was 124 mm, whereas the

finite element analysis gave a value of 96 mm.

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Figure 2.3: Torhaus Der Messe cross-section (Reul and Randolph, 2003).

2.6 Limitations of Settlement

Significant aspects of settlement from static and dynamic loads are total and

differential settlement. Total settlement is the magnitude of downward movement.

Differential settlement is the difference in vertical movement between various locations

of the structure and distorts the structure. Many structures can tolerate substantial

downward movement or settlement without cracking The most famous case of

differential settlement is the Leaning Tower of Pisa, where the South side of the towersettled more than the North side. Sowers (1962) summarized his studies into three modes

of settlements :(i) total settlement, (ii) tilting and (iii) differential movement (Table 2.1).

It shows that simple steel frames can tolerate large differential settlements, whereas high

continuous brick walls are highly sensitive to movement.

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13

Table 2.1: Maximum allowable settlements of some structures (Sowers, 1962).

Type of movement Limiting factor Maximum Settlement

Total Settlement

Drainage

AccessProbability of nonuniform settlement:

Masonry walled structureFramed structures

Smokestacks, silos, mats

15-30cm

10-60cm

2.5-5cm5-10cm

7.5-30cm

Tilting

Stability against overturning

Tilting of smokestacks, towers

Rolling of trucks; etcStacking of goods

Machine operation cotton loom

Machine operation turbo generatorCrane rails

Drainage of floors

Depends on height and

width

0.004l

0.01l0.01l

0.003l

0.0002l0.003l

0.01 - 0.02l

Differential

movement

High continuous brick wallsOne-story brick mill building, wall

cracking

Plaster cracking (gypsum)Reinforced-concrete-building frame

Reinforced-concrete-building curtain

wallsSteel frame, continuous

Simple steel frame

0.0005 - 0.001l0.001-0.002l

0.001l0.0025-0.004l

0.003l

0.002l

0.005l

Note I = distance between adjacent column that settle different amounts, or between any

two point that settle differently. Higher values are for regular settlements and more

tolerant structures. Lower values are for irregular settlements and critical structures.

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CHAPTER 3

METHODOLOGY

3.1 Introduction

The methodology for the whole study case is important as it will help to underline

the activities and important issues that need to be solved earlier. It helps the study flow

smoothly and managing the time efficiently.

Several methods were introduced to measure and predict elastic settlement

analysis in geotechnical engineering. For this study case, the author analyzed the

foundation and the soil behavior so that elastic settlement of the pile and elastic

settlement of soil could be approximated.

All the information about the geological condition and method of foundation for

KLCC twin towers was collected and analyzed. The methodology used was to

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15

fulfill the objectives as stated in chapter 1. Figure 3.1 show the flow chart process for this

study.

Data Collection

Data for the case study will be find form the site- Investigation report

- Foundation properties- Pile properties

Analysis of the case study

Interpretation of results

Conclusions

Figure 3.1: Methodology for the study.

3.2 Data Collection

The Data needed for this study will be finding from several resources such as:-

i) Article.ii) Journaliii)Site Investigation Reportiv)Conference Paper

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17

Figure 3.2: KLCC Foundation Profile (Hamdan, 1994).

Figure 3.3: Layout Plan for Barrette Pile (Hamdan, 1994).

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3.3.1 Geological Condition

The tower geological condition referred to research by Ranhill Bersekutu Sdn

Bhd show that there are several soil layers formed by Metasedimentray formation such as

siltstone, shale and phyllite (known as Kenny Hill) followed by Kuala Lumpur

Limestone(Figure 3.4 and 3.5). Kenny Hill formation can be eroded because it is of soft

elements. To solve these problems, floating raft foundation was used to prevent or

reduce the differential settlement of the soils to happen (Hamdan, 1994).

Figure 3.4: Kuala Lumpur geological schematic (Ooi, 1986).

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Legend

Figure 3.5: Based Rock around Kuala Lumpur (Ooi, 1986).

3.4 Elastic Settlement of Soil

The immediate settlement of a structure on cohesive soil consists of elastic

distortion associated with a change in shape without volume change and, in unsaturated

clay, settlement from a decrease in volume (Das, 1999). The theory of elasticity is

generally applicable to cohesive soil. Janbu et al. (1956) proposed a generalized for

average immediate settlement for uniformly loaded flexible footings. Using Janbu

approximation,

0

0 1

s

q BHE

= (3.1)

Where,

1 = correction factor for finite thickness of elastic soil layer (refer Figure 3.6a)

0 = correction factor for depth of embedment of footing, Df(refer Figure 3.6b)

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B = width of rectangular loaded area of diameter of circular loaded area

qo = load per unit area

The 0 and 1 chart were modified by Christian and Carrier (1978) and were replaced

with A1 and A2 charts. Therefore,

0

1 2

s

q BH A A

E = (3.2)

Figure 3.6a: Correction factor for finite thickness of elastic soil layer (Das, 1999).

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21

Figure 3.6b: Correction factor for depth of embedment of footing, Df(Das, 1999).

3.5 Elastic Settlement of Piles

The settlement of a pile under a vertical working load (Qw) is caused by three

factors:

1 2 3s s s s+ += (3.3)

where,

s = total pile settlement

s1= settlement of pile shaft (shortening)

s2 = settlement of pile caused by the load at the pile point

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s3 = settlement of pile caused by the load transmitted along the pile shaft

The procedures for estimating the preceding three elements of pile settlement are as

follows:

a) Determination of s1

If one assumes the pile material to be elastic, then the deformation of the pile

shaft can be evaluated using the fundamental principles of mechanics of materials:

1( )wp ws

p p

Q Qs

A E

L+= (3.4)

where,

Qwp = load carried at the pile point under working load condition

Qws= load carried by frictional (skin) resistance under working load condition

Ap = area of pile cross section

L = length of pile

Ep = Youngs modulus of the pile material

= depend on the nature of unit frictional

The magnitude of will depend on the nature of unit frictional (skin) resistance

distribution along the pile shaft. If the distribution offis uniform or parabolic in nature as

shown in Figure 3.7a and Figure 3.7b, is equal to 0.5. However for triangular

distribution of (Figure 3.7c), the value of is about 0.67 (Vesic, 1977).

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25

The values of Cp for various soils given in table 3.2

Table 3.2: Typical Values of Cp (Das, 1999).

Soil Type Driven Pile Bored Pile

Sand(dense to loose 0.02-0.04 0.09-0.18Clay(stiff to soft) 0.02-0.03 0.03-0.06

Silt(dense to loose) 0.03-0.05 0.09-0.12

c) Determination of s3

The settlement of a pile caused by the load carried by the pile shaft can be given

by a relation similar to Eq. 3.5 or

32( ) (1 )

wss ws

s

Q DI

pL E= (3.7)

where,

p = perimeter of the pile

L = embedded length of pile

Iws = influence factor

The term Qws / pL in the equation is the average value offalong the pile shaft. The

influence factorIws can be expressed by a simple empirical relation as

2 0.35w sL

ID

= + (3.8)

Vesic (1977) also proposed a simple empirical relation similar to Eq. 3.6 for obtaining s 3

as

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3w s sQ C

sL q

= (3.9a)

where,Cs = an empirical constant = (0.93 +0.16(L/D)Cp (3.9b)

The values of Cp for use in Eq. 3.9a can be estimated from Table 3.2

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CHAPTER 4

ANALYSIS AND RESULTS

4.1 Introduction

From the site investigation report of the tower site, the analyses of the soil

characteristic were done. The site investigation report taken from KLCC Holdings

Berhad was the site investigation report for Lot 171 (Lot C), KLCC, i.e., is approximately

50 m from the actual tower area. Based on the information from the boreholes log, the

soil profile was drawn accordingly in order to have a schematic idea of the soil condition

at the tower site.

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4.2 Parameters

Parameters of the soil calculated were based from the site investigation report of

the site. The important soil parameters used to calculate the consolidation settlement of

group piles were the void ratio (), compression index (Cc) and saturated unit weight

(sat).The liquid limit obtained from each borehole distribute into its range and the

average reading. The average reading then taken to estimate Cc value for each layer.

Several equations that were used to determined the parameters for soil layer is as follows:

1. Void Ratioe = swG (4.1)

where, Gs = specific gravity of the soil

w = moisture content (%)

2.

Compression IndexThe value of Cc depends on the type of soil. Skempton (1944) made an empirical

correlation for the value of compression index which is

(4.2)cC = 0.009(LL - 10)

where, Cc = compression index

LL = Liquid limit

3. Saturated Unit Weight of SoilThe saturated unit weight of soil can be determined as

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s sat

satG +

=1 +

we

e

(4.3)

where, w = unit weight of soil =9.81

Gs = specific gravity of the soil

sat = saturated unit weight of soil.

e = void ratio

4.3 Soil Profile

Each parameter of each layer of soil was determined from the equation stated

above. The soil profile for the site was based from the borehole log and it was found that

3 types of residual soils laid under the tower, i.e., is that is sandy silt, clayey silt and silty

gravel. But silty gravel was only found in borehole 2, 8 and 10 and can be negligible. So

there were 3 layers of soils with 2 major type of soils (refer Figure 4.1)

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32

0.316 2.70

0.8532

e =

=

2. Compression Index0.009(41.0 10)

0.2790

cC =

=

3. Saturated Unit weight of soil

3

2.70(9.81) 0.8532(9.81)

1 0.8532

18.809 kN/m

sat+

=+

=

Figure 4.2: Schematic of foundation and soil profile for KLCC towers.

4.4 Settlement Analysis

4.4.1 Calculation for Elastic Settlement of soil

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CHAPTER 5

CONCLUSIONS

5.1 Introduction

Many different methods are used to estimate the settlement analysis. The classical

method of Karl Terzaghi that is Theory of One Dimensional Terzaghi which is used

widely for predicting consolidation settlement. The concept of this theory then is

modified by other researchers around the world. Several methods were introduced to

estimate settlement such as by Janbu (1956), Versic (1977), and Bjerrum (1972).

Settlement analysis is important before the commencement of a building

construction. It is used to determine the settlement and to design the right foundation for

the buildings. One of the most famous works on the topic of allowable settlements is by

Skempton and MacDonald (1956) who studied the performance of ninety-eight buildings

of load bearing wall, reinforced concrete and steel frame construction founded on various

foundation systems.

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37

meshing method. Analysis of differential settlement also important for towers because of

the large loading and the conditions of the soil profile can give a high value of differential

settlement that can cause the towers to tilt. So it is necessary for the consultants and

contractors to make an analysis of the total settlement and also the differential settlement

before any constructions.

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39

Patrick, J. F (2003), Consolidation And Settlement Analysis. CRC Press LLC.

Reul, O. & Randolph, M. F. (2003), Piles Rafts in Overconsolidated Clay: Comparison

of in situ measurements and numerical analysis. Gotechnique 53, No. 3, 301-315.