workplace safety and health practices award constructi… · 1 site preparation (erect traffic...

Workplace Safety and Health

Practices Award:

Gammon Construction Limited Singapore Branch

Simplified Traffic Diversions and Safe Earth Retaining System

Workplace Safety & Health Awards 2007

Simplified Traffic Diversions and Safe Earth Retaining System

for the Construction of DTL Chinatown Station / Tunnels Roof

Slabs

Safety

Agenda

1. Introduction

2. Original & Innovative Safety Solution

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3. Comparisons

4. Evaluations

5. Conclusion

1. Introduction

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Gammon Construction Singapore Branch

• A1 Contractor in both Building & Civil Engineering

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Construction Project – Contract 909

- Design, Construction and Completion of Chinatown

Station and associated tunnels for Downtown Line 1

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• Client : Land Transport Authority of Singapore

• Design Consultant : Lambeth (Gammon’ wholly

Subsidiary Company)

• Main Contractor : Gammon Construction Limited

Contract 909 – Site Overview

Overrun Tunnels Retail Area and Tunnels

C909 | C908C909 | C908

Existing Underpass

Chinatown Station

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C909 Chinatown Station Layout PlanC909 Chinatown Station Layout Plan

Existing NEL Chinatown

Station

ShopHouses

Structural Arrangement

- Diaphragm wall - 2 rows Tension piles

- 3-level Slabs (Roof & Retail & Track) - Internal wall & Column

Roof

PermanentTemporary

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Roof

Retail

Track

D-wall

Column/WallStanchion

Construction Method

• Top-down construction

• 2-phase traffic diversion

• Early backfilling for road reinstatement

• Shallow cofferdam for roof construction

Work Area Work AreaDivert Road

Divert Road

Roof Cofferdam

Roof

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Phase 1 Phase 2

BackfillCofferdam

Roof Cofferdam

2a. Original Safety Solution

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2a. Original Solution - Sheet pile + Strutting – Stage 1©

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2b. Innovative Safety Solution

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2b. Innovative Solution – Precast Retaining wall©

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Construction Photos

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Pre-cast retaining wall installationStrutted cofferdam and

Construction of roof slab

Construction Photographs©

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Pre-cast retaining wall installation

Backfilling & Road reinstatementRemoval of Struts and waterproofing

Construction of roof slab

South Side Excavation©

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North Side Excavation©

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3. Comparisons

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Major Improvements

Works Involved Original Scheme Innovative Scheme

General Mobilisation /

Demobilisation of machineries 3 stages 2 stages

Site Preparation 3 stages 2 stages

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Major Traffic Diversions 3 stages 2 stages

Sheetpiles 4 rows 1 row

Struttings 3 layers 1 layer

Major Excavation Phases 3 stages 2 stages

Major Construction Joints 2 1

3a. Lesser Risk/Hazard Exposure

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Project Achievements

• No accident related to this Safety Solution.

• The project has no accident, stop work order nor fine.

• The project achieved over 4 million accident-free man-

hours.

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• Project received the following safety recognitions;

- WSH Council’ SHARP awards – 2009, 2010 and 2011

(submitted and pending outcome),

- LTA’ ASAC Safety Champion 2010,

- BCA’ Productivity & Innovation Award 2011,

- UK’ ROSPA Gold Award 2010 & 2011.

3b. Time Saving

- 90 Working Days

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3c. Cost Saving

- Closed to S$1 Million

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Cost Comparison:

Work Scope Cost for 3 phase S$ Cost for 2 phase S$

1 Site preparation (erect traffic barrier and hoarding) for 3 phase construction 275,000.00 200,000.00

2 Traffic diversion cost for traffic diversions 95,000.00 65,000.00

3 Road cutting & Road reinstatement cost for diversions (mobilization of rollers, material costs, road marking cost) 725,000.00 625,000.00

4 Sheetpiling cost for 2 rows of sheet pile ( mobilization cost of using silent piler, sheetpile cost, extraction cost) 800,000.00 400,000.00

5 Strutting works for North & South Cofferdam ( mobilization cost, machinery cost (lorry crane, mobile crane, generator

set for welding) material cost (walers, struts, struts, G30 concrete packing), labour cost) 1,000,000.00 500,000.00

Cost for having 2 construction joints on roof slab including (hy-rib formwork, hydrophilic water-stop, re-injectable grout

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Estimated Overall Cost Savings ≈ $1M

6Cost for having 2 construction joints on roof slab including (hy-rib formwork, hydrophilic water-stop, re-injectable grout

tube, labour cost, additional coupler costs, additional lapping bars cost, additional waterproofing cost – ie. Lapping of

waterproofing) 350,000.00 240,000.00

7 Additional Design cost - 707.50

8 Precast retaining wall - 529,000.00Sub-Total $3,245,000.00 $2,559,707.50

Estimated cost saving

9 Estimated Mandays cost = 30% of the cost savings

10 Therefore Total Cost Savings

$685,292.50

$364,500.00

$1,049,792.50

3d. Improved Productivity

- 4,500 man-days reduction

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3e. Other Benefits

-Client Satisfaction

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-Material Saving – Less Sheet-piles used

-Environmental Friendly – Less CO2 emission

Conclusion

• A comprehensive engineering solution that reduced hazard

/ risk and delivered good safety results.

• Cost saving of $1,000,000.

• Productivity improvement of 4,500 man-days.

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• Time saving of 90 working days.

• First of its kind in Singapore and favored by LTA for future

adoption.

• Successfully implemented and achieved the desirable

results.

ZERO HARMAcross our businesses by 2012

Thank You

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