Finger 1 Project_ERSS Report for Temporary Drain Diversion_23 Sep 2014

8/11/2019 Finger 1 Project_ERSS Report for Temporary Drain Diversion_23 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: ?????

d


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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

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

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 WaTable 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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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 5m deep excavation using the proposed 15m penetratio

wall is checked against the loss of stability due to piping. Embedded dis therefore 10m.

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 FSP IV sheetpile wall is carried out u

PLAXIS version 9 .The typical construction sequences for the drain

(i) Install FSP IV sheetpile wall to toe depth of 9m 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) 90%EI is considered for the FSP IV sheetpile wall.

v) Groundwater table taken to be +3.0mCD behind the sheetpile w

side of the sheetpile wall.

vi) Seepage analysis is considered in the PLAXIS analysis


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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:-


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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. Ththe 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. Based on the modified Bishops method, the mimimum facto

cut slope is summarized in Table 5. Weep holes are to be provided

the concrete lining of the drain.


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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 K

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

Our Ref No: SNP 27-09R1 K

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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Our Ref No: SNP 27-09R1

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 15.0 2.2 > 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 (with 0.5munplanned excavation) fortemporary Drain

16mm (RHS)17mm(LHS)

132kNm/m133kNm/m

BSand surcharge placed behind RHSSheetpile after completion ofexcavation for temporary drain

35.5mm (RHS) 154kNm

Note: (i) Elastic modulus of Sand assumed to be E=13000kPa

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

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 150mm

thick 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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Finger 1 Project_ERSS Report for Temporary Drain Diversion_23 Sep 2014

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