BEHAVIOUR OF GRAVITY CAISSON ON SANDBED
type: CreativeWork
description: Gravity caissons are proposed as the wharf structure for the Port of Singapore Authority's (PSA) Third Container Terminal. Conveyance of cargo at this terminal will be undertaken by new pilotless automated guided vehicle (AGVs) operation which may be adversely affected by ground movement exceeding 1/30 between 2 points over a distance of 3m. In addition, efficiency and utilisation rate of a quay crane used to service quay-side container handling operations may be severely affected by a differential level between the front and rear crane rails exceeding l/500 over a distance of 35.6m. Thus, there is a need to study the movement of the gravity caissons as well as that of the reclaimed land behind it wider the anticipated construction and working loads. This is the task of an on-going joint PSA-NUS (National University of Singapore) research programme.The effects of sandbed relative density (RD), caisson base width, the presence of rock-sill overlying sandbed and sandbed thickness were studied by means of centrifuge model tests on the NUS geotechnical centrifuge. The simulated construction sequences included infilling of caisson, backfilling of caisson and live load imposition on the caisson. The centrifuge studies showed that the caisson would generally settle uniformly during the infilling stage. During thebackfilling and live loading stages, it would settle further with some tilting and sliding in the seaward direction whereby the maximum movement was observed around the caisson toe. The results indicated that the caisson settlement decreased as the sandbed RD increased. Then, asthe caisson base width was reduced from 18m to 14m, the settlement was relatively unaffected while the horizontal movements were significantly large for the 14m caisson. The smaller caisson width of 14m may not have sufficient selfweight to prevent sliding and tilting failure during the backfilling stage. Furthermore, the presence of rock-sill overlying the sandbed was found to be effective …
abstract: Gravity caissons are proposed as the wharf structure for the Port of Singapore Authority's (PSA) Third Container Terminal. Conveyance of cargo at this terminal will be undertaken by new pilotless automated guided vehicle (AGVs) operation which may be adversely affected by ground movement exceeding 1/30 between 2 points over a distance of 3m. In addition, efficiency and utilisation rate of a quay crane used to service quay-side container handling operations may be severely affected by a differential level between the front and rear crane rails exceeding l/500 over a distance of 35.6m. Thus, there is a need to study the movement of the gravity caissons as well as that of the reclaimed land behind it wider the anticipated construction and working loads. This is the task of an on-going joint PSA-NUS (National University of Singapore) research programme.The effects of sandbed relative density (RD), caisson base width, the presence of rock-sill overlying sandbed and sandbed thickness were studied by means of centrifuge model tests on the NUS geotechnical centrifuge. The simulated construction sequences included infilling of caisson, backfilling of caisson and live load imposition on the caisson. The centrifuge studies showed that the caisson would generally settle uniformly during the infilling stage. During thebackfilling and live loading stages, it would settle further with some tilting and sliding in the seaward direction whereby the maximum movement was observed around the caisson toe. The results indicated that the caisson settlement decreased as the sandbed RD increased. Then, asthe caisson base width was reduced from 18m to 14m, the settlement was relatively unaffected while the horizontal movements were significantly large for the 14m caisson. The smaller caisson width of 14m may not have sufficient selfweight to prevent sliding and tilting failure during the backfilling stage. Furthermore, the presence of rock-sill overlying the sandbed was found to be effective …
author: EUGENE KHOO
keywords: Caisson, Relative Density, Infilling, Backfilling, Liveloading
date published: 1995
date modified: 2026-07-24T03:31:26Z
provider: National University of Singapore
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: National University of Singapore