Finger 1 Project_ERSS Report for Temporary Drain Diversion_24 Sep 2014

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GEOTECHNICAL DESIGN REPORT

ON

PROPOSED TEMPORARY WORKS FOR TEMPODIVERSION

FOR

PROPOSED RECLAMATION AT TUAS FINGER O

BCA Project Ref. Number: ?????

h


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Geotechnical Design Report for Proposed Temporary Works

On Temporary Drain Diversion for Proposed Reclamation at Tuas Finger One

for Penta-Ocean Construction Co., Ltd

TABLE OF CONTENT

1. INTRODUCTION .....................................................................................1.1 Background.................................................................................................

1.2 Design Codes ..............................................................................................

2. GENERAL DESIGN CONSIDERATION .............................................2.1 Site Investigation Boreholes ........................................................................

2.2 Assumed Soil Model...................................................................................2.3 Proposed Design Parameters .......................................................................

2.4 Ground Water Table ...................................................................................

2.5 Surcharge Load Condition...........................................................................

3. LIMIT STATE EQUIBRIUM OF PROPOSED SHEETPILE WALL3.1 Stability against Piping Failure....................................................................

3.2 Stability against Toe Failure ........................................................................

4. GEOTECHNICAL DESIGN OF PROPOSED SHEETPILE WALL..4.1 Assumptions ...............................................................................................

4.2 Results of FEM Analysis .............................................................................

4.3 Risk Assessment to Surrounding Buildings................................................

5. STRUCTURAL DESIGN OF PROPOSED SHEETPILE WALL........

6. STRUCTURAL DESIGN OF STRUT AND WALER...........................6.1 Proposed Strut Spacing...............................................................................

6.2 Strut and Waler Design...............................................................................7. OPEN CUT SLOPE..................................................................................

8. PROPOSED INSTRUMENTATION PLAN..........................................

APPENDIX

A BOREHOLE LOGS IN VINICITY OF PROPOSED DRAIN

B RESULTS OF SEEPAGE ANALYSIS OF PROPOSED SHEET

TEMPORARY DRAIN BY SEEP/W

C TOE STABILITY CALCULATION ON PROPOSED SHEETP

D RESULTS OF FEM ANALYSIS OF PROPOSED SHEETPILE

TEMPORARY DRAIN BY PLAXIS


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LIST OF FIGURES

Figure 1 Schematic Plan of Proposed Temporary Work on Temporary Dra

Figure 2 Location Plan of Boreholes in vinicity of Proposed Temporary D

Figure 3 Proposed Soil Model

Figure 4 Schematic Sketch of Proposed Strutting System

Figure 5 Results of Slope Stability Analysis of Proposed 1V: 2H Cut Slope

Drain

Figure 6 Plan View on Schematic Sketch on Interface between Sheetpile W

Cut Slope

LIST OF TABLES

Table 1 Proposed Geotechnical Parameters for Temporary Works

Table 2 Results of Toe Stability for Temporary Sheetpile Wall

Table 3 Summary on FEM Results on Proposed Temporary Works for Te

Table 4 Proposed Strut and Waler Members for Temporary Sheetpile Wa

Table 5 Results of Open Cut Slope Analysis for the Outlet of Temporary

Table 6 Proposed Instrumentation and Review Level


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STANDARD CERTIFICATION BY THE QUALIFIED PERSON

WORKS

1. In accordance with Regulation 9 of The Building Control Regulations

Qualified Person for structural works appointed under section 8(1)(a) or

Control Act, hereby submit the detailed structural plans and design calcul

certify that they have been prepared in accordance with the provisions

Regulations, the Building Control Act and any other written law peconstruction for the time being in force

2. I further certify that these detailed structural plans and design calculations

Project Ref No: .

3. Total number of structural plans submitted : ___.and total number of pag

in this book 1 ___

__________________________________________ SE

QUALIFIED PERSON FOR STRUCTURALSIGNATURE & STAMP


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1. INTRODUCTION

1.1 Background

In this ST??? submission, this report describes the temporary work

sheetpile wall for the drain diversion for the above-captioned projec

about 5m deep by 4m wide and according to the construction stage

Penta-Ocean Construction Co., Ltd, a 5m high sand surcharging wi

awy from the edge of the temporary sheetpile wall once the drain

However, the outlet of the drain facing the sea will be constructed by

are no sand surcharging planned at this area as shown in Figure 1.

Typical details of the sections in the QPs design is summarized as fo

Proposed ERSS Proposed

Platform

Level

(m CD)

Final

Formation

level for

Drain

Diversion

(m CD)

Excavation

Depth (m)

Proposed

Sheetpile

toe

CD)/Slop

system

Type 1 :FSP IV

(S275) sheetpile

wall with 1-

level strut

+6.0m +1.0m 5m -6m CD

(12m

penetratio

length)

Type 2: Open

Cut slope at

Drain Outlet

+6.0m +1.0m 5m 1 V: 2H

Note: ERSS Earth Retaining Stabilizing System

* Assuming sand unit weight of 17 kN/m3for the sand surcharging


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2. GENERAL DESIGN CONSIDERATION

2.1 Site Investigation Boreholes

There are no boreholes conducted at the proposed drain diversion

boreholes TBH-35 and TBH-36 located in the vinicity as shown in Fi

these 2 boreholes, the ground condition comprises of reclaimed sand

the Jurong Formation. No Kallang Formation is found at these tw

presents the two boreholes.

2.2 Assumed Soil Model

Based on the above nearby boreholes and the information that the arelocated within the exising sandkey, we inferred that the reclaim

throughout the entire site for the proposed drain. The assumed soil m

diversion is as depicted in below Figure 2.

Reclaimed Sand

(N=19 to 35)


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2.3 Proposed Design Parameters

The geotechnical design parameters proposed for the temporary w

Table 1.

2.4 Ground Water Table

The groundwater table is assumed:-

Seawater level : +3.0m CD (HWMS)

2.5 Surcharge Load Condition

Surcharge load of 10kPa was adopted behind the proposed sheetpile w

3. LIMIT STATE EQUIBRIUM OF PROPOSED SHEETPIL

3.1 Stability against Piping Failure

The proposed 12m penetration length FSP IV sheetpile wall is checke

stability due to piping. For an excavation depth of 5m, the embedded wall is therefore 7m.

The factor of safety, FSpipingagainst piping is calculated using the follo

FSpiping = Downward total weight of soil mass

Average Upward Seepage pressure

The average upward seepage force us is estimated using a seepage pr


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3.2 Stability against Toe Failure

The stability against toe failure is calculated using strength factor m

parameters are used. The minimum factor of safety obtained using the

summarized in Table 2. Appendix C presents the toe stability cal

sheetpile wall.

4. GEOTECHNICAL DESIGN OF PROPOSED SHEETPILE

The design of the proposed Type 1: FSP IV sheetpile wall is carr

program PLAXIS version 9 .The typical construction sequences for

follows:-

(i) Install FSP IV sheetpile wall to toe depth of 6m CD. Platform

(ii) Excavate to +5.0m CD and then install strut @ +5.5m CD.

(iii) Final excavation to formation level +1.0mCD.

(iv) Construct a 150mm thick lean concrete at the formation level

(v) Placement of +11.0m CD high sand surcharging at 11m

sheetpile wall after the completion of the drain excavation to +

4.1 Assumptions

The assumptions made in the retaining wall analysis by PLAXISar

i) 0.5m unplanned excavation is considered.

ii) Drained parameter is used for Reclaimed sand.iii) Surcharge of 10 kPa is considered.

iv) Preload to +11m CD is considered as surcharge in the FEM as

weight of 17.5 kN/m3.

v) 90%EI is considered for the FSP IV sheetpile wall


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4.3 Risk Assessment to Surrounding Buildings

There are no nearby structures within 2 times the excavation depth o

work. Therefore, there is no impact assessment of the proposed

surrounding ground and structures.

5. STRUCTURAL DESIGN OF PROPOSED SHEETPILE W

The ultimate bending moment capacity, Mc, of the FSP IV sheetpile w

follows:-

Mc= py . Zxx = 624 kNm

Where, py= Yield stress of steel = 275 N/mm

Zxx= Section Modulus of FSP IV sheetpile = 2270 cm3/

From Table 2, the maximum unfactored bending moment of FSP IV s

works is 154kNm. Using a load factor of 1.4, the ultimate bending m

to be:-

Mult= 1.4 x 154kNm = 216 kNm < Mc -----------

6. STRUCTURAL DESIGN OF STRUT AND WALER

6.1 Proposed Strut Spacing

The proposed strut spacing for the temporary sheetpile wall is 5m

schematic sketch:-

5m

Sh


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6.2 Strut and Waler Design

The steel strut is designed as compression member to resist the lat

temporary retaining wall while the waler is designed as bending elem

earth loads from the temporary retaining wall to the steel strut. Bo

waler member are designed in accordance to BS 5950 : 2000 and

design considerations are taken into the steel and waler design:-i) Increase of axial force arisng from 10 degree increase in tem

accordance to TR26 : 2010 Technical Reference for Deep E

SPRING Singapore.

ii) Eccentricity of axial load at the connection. For waler of sing

shall be about 10% of the overall dimension of the strut in the

iii) Accidential impact load of 50 kN as in accordance to Reference for Deep Excavation published by SPRING Sing

iv) One strut failure is also considered in the strutting design usi

in accordance to TR26 : 2010.

The proposed strut and waler members are summarized in Table 4. Th

the strut and waler are presented in Appendix E.

7. OPEN CUT SLOPE

The open cut slope for the outlet of the temporary drain will be const

horizontal slope with a 150mm thick lean concrete lining (Grade 15)

mesh. Weep holes are to be provided along the slope surface of the co

We used a slope stability program SLIDE version 3 developed by

the factor of safety for the proposed cut slope.

Based on the modified Bishops method, the mimimum factor of safe


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We propose the inclinometers and ground settlement markers locate

proposed temporary work. For the open cut slope, we propose on

markers. Table 6 summarizes the proposed review levels for the abov


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On Temporary Drain Diversion for Proposed Reclamation at Tuas Finger One for Penta-Ocean Construction Co., Ltd

Our Ref No: SNP 27-09R1

Figure 1 Schematic Plan of Proposed Temporary Work on Temporary Drain


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On Temporary Drain Diversion for Proposed Reclamation at Tuas Finger One for Penta-Ocean Construction Co., Ltd


Figure 2 Location Plan of Boreholes in vinicity of Proposed Temporary Drain

Boreholes TB

TBH-36 in vi

proposed Dra

Proposed Drain


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Table 1 Proposed Geotechnical Parameters for Temporary Works

Effective ShearStrengthGeological

FormationSPT N-value

BulkDensity(kN/m

3)

UndrainedShear

Strength, cu(kPa) c',

(kPa)'

(deg)

UnDeMo

Reclaimed Sand 19-36 20 - 0 30

JurongFormation(30


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Table 2 Results of Toe Stability for Temporary Sheetpile Wall

Proposed

Ground

Level (m

CD)

Proposed Final

Excavation level (m

CD)

Toe Pentration length

from proposed

ground level (m)

Factor of safet

Strength Facto

Method

+6.0 +1.0 12.0 1.8 > 1.0 (allo


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Table 3 Summary on FEM Results on Proposed Temporary Works

Stage Condition Max. sheetpiledeflecton

Max. bendingmoment

AExcavation to FEL +1.0m (with0.5m unplanned excavation) fortemporary Drain

16.5mm (RHS)16.0mm(LHS)

132kNm/m (RHS132kNm/m (LHS

B

Sand surcharge placed behindRHS Sheetpile after completionof excavation for temporarydrain

33.5mm (RHS) 132kNm/m

Note: (i) RHS : Right Sand Side Sheetpile wall and LHS: Left Hand Side Sheetpile

* Ultimate axial stress on 250mm thick concrete slab = 1.4 x 39x103/(250x1000) = 0.2

BRC A-10 for the reinforcement for 250mm thick lean concrete

Stage A: Excavation for the construction of temporary drain

Stage B: Placement of Sand surcharging @ 11m behind the RHS sheetpile


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Table 4 Proposed Strut and Waler Members for Temporary Sheetp

Member Type Steel section/Grade

Steel Strut 1 H300, 94kg/m (S275) @ 5m c/c*

Steel Waler 1 H400, 172kg/m (S275)

* With splay member


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Table 5 Results of Open Cut Slope Analysis for the Outlet of Tempo

Proposed SlopeLevel at Crest

of SlopeLevel at Toe

of SlopeMinimum fact

1 vertical to 2horizontal with 150mmthick lean concrete

(with BRC A8)**

+6.0m CD +1.0m CD 1.96 > 1.5 (allow

* Based on Modified Bishop Method


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Figure 5 Results of Slope Stability Analysis of Proposed 1V: 2H Cut Slo

150mm thick lean concrete (Grade 15) w

BRC A8 mesh. Weep hole to be provide1.5m c/c


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Figure 6 Plan View on Schematic Sketch on Interface between Sheetpile

1V: 2H

concre

1.5n c

FSP IV sheetpile Wall

Strut @ 5m c/c with splay

member


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Finger 1 Project_ERSS Report for Temporary Drain Diversion_24 Sep 2014

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