ABSTRACT

ThispaperdescribesthestrengthanddeformationbehaviourofJurongFormationsedimentary rocks in Singapore. In this study, uniaxial and triaxial compressive tests as well as indirect tensile tests had been carried out on different sedimentary rocks, i.e. siltstone, limestone, sandstone and mudstone. During the tests, the axial and lateral deformations of the rocks were monitored against the stress level. In addition, acoustic emission and change in ultrasonic velocities during loading wererecordedaswell. Variousaspectsoftherockbehavioursuchasstressthresholds identification,effectsofconfiningpressureonstressthresholds,acousticemissiontests, ultrasonic tests, Young's modulus and Poisson's ratio and failure criteria were elaborated in this paper.

1 INTRODUCTION

Duetothescarcityandhighcostoflandsurfacearea, Singapore has looked into expanding its infrastructure to the underground. A well known example of such project isthe UndergroundAmmunitionFacility(UAF)(Fig. 1 &2),developedbyDefenceScience&Technology Agency(DSTA)in April1999(Innovation,2002). The UAFisbuiltintoaformergranitequarryinMandai (Bukit TimahGranite),whichhassixtimesthestrength ofnormalconcrete. Inaddition,byconstructingthe facility underground, the builders saved 300 hectares – a land area equivalent to 400 soccer fields, or half the size of Singapore's Pasir Ris New Town.

(Figure in full paper)

Underground space could offer advantages such as the following:-

  • more efficient use of land;

  • better environmental quality;

  • strategic storage of essential resources; and

  • a higher degree of safety.

Suchspacecan beutilizedforsewagetreatment plants, oil and gas storage, shelter and recreation centers, water collection and storage, power stations, underground pumpedstorage,militaryinstallationsandindustrial waste repositories. With all these added advantages, itis worthwhiletodevelopundergroundfacilitiesinother rock formations of Singapore.

Thetwo mainformationsconsideredsuitabletohost underground caverns are the Bukit Timah Granite and the JurongFormation(sedimentary). Severalotherstudies were done,including a study onthe feasibility of cavern developmentintheJurongFormation(1995)andthe feasibility of developing the Underground Science City at KentRidge(1997). Afterthesuccessfulcompletionof theUAF,thefeasibilityofanundergroundpetroleum storagefacilitiesinrockcavernbelowJurongIsland (2001)wasinvestigated(CivilEngineeringResearch, 2002).

2 JURONG FORMATION

The Jurong Formation covers the western and southwestern part of Singapore Island. It is mainly made up of sedimentary rocks from the upper Triassic and lower to middle Jurassic age (230 ~ 180 million years ago). Some of these rocks include mudstone, shale,

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