Showing papers by "Arul Arulrajah published in 2004"

Observational method of assessing improvement of marine clay

Abstract: The ongoing Changi East Reclamation Project in Singapore consists of land reclamation and ground improvement works of the foreshore for the future expansion of the Changi International airport and associated facilities. Reclamation works in the project involve the hydraulic placement of sand-fill over the seabed, which is underlain by thick, highly compressible Singapore marine clay. Ground improvement works in the project comprise the installation of vertical drains and the subsequent placement of surcharge to accelerate the consolidation of the underlying marine clay. A pilot test site was carried out in the project, comprising three sub-areas that were installed with vertical drains at various spacings, plus a fourth untreated sub-area. The four sub-areas were surcharged simultaneously and preloaded for a duration of 32 months. A comprehensive field instrumentation programme was implemented in the pilot test site, comprising settlement plates, deep settlement gauges, piezometers and water standpipes. T...

Piezocone dissipation testing of Singapore marine clay at Changi

Abstract: In-situ dissipation tests provide a means of evaluating the in-situ horizontal coefficient of consolidation and horizontal hydraulic conductivity of marine clays. Dissipation tests by means of piezocone were utilised in the characterisation of the horizontal coefficient of consolidation and horizontal hydraulic conductivity of Singapore marine clay at Changi in a land reclamation project. Piezocone dissipation tests were carried out prior to reclamation as well as after ground improvement with vertical drains to compare the changes in the horizontal coefficient of consolidation and horizontal hydraulic conductivity prior to and after ground improvement. The quasi-static piezometric pressures from the dissipation tests were compared with piezometric pressures from piezometers to determine their possibility of future use as an alternative to piezometers. Post-improvement CPTU dissipation tests were carried out in the treated "Vertical Drain Area" as well as in an adjacent untreated "Control Area" for comparison purposes. This study provides support for the use of piezocone dissipation testing methods for the determination of the horizontal coefficient of consolidation and horizontal hydraulic conductivity of marine clays in the region as well as an alternative to piezometer instrumentation for monitoring of piezometric pressure during consolidation. (A)

Field instrumentation monitoring of land reclamation projects on marine clay foundations

Abstract: In land reclamation on marine clay formations, grou nd improvement works are often necessary to be carr ied out in order to negate future settlement under the project ed dead and live loads. In the case of thick deposi ts of marine clay, it is necessary to accelerate the consolidation proces s. The use of prefabricated vertical drains with pr eloading option is the most widely-used ground improvement method for such cases. The degree of improvement attained by t he marine clay has to be ascertained to confirm whether the s oil has achieved the required degree of consolidati on to enable surcharge removal. This analysis can be carried out by means of observational methods for which continuous records of ground behavior can be monitored from the date of i nstrument installation. Field instruments installed , monitored and analyzed in such projects include settlement plates , deep settlement gauges, earth pressure cells, pne umatic piezometers, electric piezometers and water-standpipes. The type of field instrumentations installed and their meth od of analysis is discussed in this paper. Field instrumentation read ings obtained at a Case Study Area comprising a Ver tical Drain Area (1.5 m x 1.5 m) and an adjacent Control Area (No Drain) in the land reclamation project are also discu ssed in this paper.

Field Instrumentation Assessment of Offshore Land Reclamation Works

Abstract: The Changi East Reclamation Project in the Republic of Singapore necessitated offshore land reclamation for the future airport and associated facilities. Ground improvement works in the project comprise the installation of prefabricated vertical drains and the subsequent placement of sand surcharge to accelerate the consolidation of the underlying soft marine clay. In such ground improvement projects in soft soil, the degree of improvement attained by the marine clay has to be ascertained to confirm whether the soil has achieved the required degree of consolidation to enable surcharge removal. This analysis can be carried out by means of observational methods for which continuous records of ground behavior can be monitored from the date of instrument installation. The Case Study Area conducted in the reclamation site consisted of a Vertical Drain Area and an adjacent untreated Control Area. Both areas were fully instrumented and monitored to compare the degree of consolidation of the areas close to the surcharge removal period. Instruments installed, monitored and analyzed in the Case Study Area include settlement plates, deep settlement gauges, pneumatic piezometers, electric piezometers and water stand-pipes. This paper discusses the methodology of land reclamation as well as the suitable types of field instrumentation for such projects.

Preloading and prefabricated vertical drains design for offshore land reclamation projects

Abstract: The Changi East Reclamation Project in Singapore necessitated land reclamation in off-shore conditions. The project comprises the installation of prefabricated vertical drains and the subsequent placement of surcharge to accelerate the consolidation of the underlying marine clay. This paper discusses the various theories, considerations and design methodologies for the ground treatment of marine clay with prefabricated vertical drains in such off-shore land reclamation projects. For the covering abstract see ITRD E125180.

Ground improvement techniques for the treatment of high-speed railway embankments

Abstract: A high-speed railway project is currently being con structed between Rawang and Bidor in Peninsular Malaysia. The ground improvement methods adopted in the project are vibro replacement with stone columns, dry deep s oil mixing (cement columns), geogrid reinforced piled embankments with individual pile-caps and removal/replacem ent works. This paper provides a detailed look into the vibro replacement with stone columns and dry deep soil mixing treatment methods while also providing an overview into the other treatment methods implemented in the high-speed railway project. The use of plate bearing tests and field i nstrumentation to monitor the performance of the st one columns and dry deep soil mixing ground treatment methods is al so discussed.

Factors affecting assessment and back-analysis by piezometer monitoring

Abstract: Prefabricated vertical drains with preloading optio n are the most widely-used ground improvement method for the improvement of marine clays in land reclamation projects. The assessment of the degree of consolidatio n of the marine clay is of paramount importance prior to the remova l of preload in such ground improvement projects. This analysis can be carried out by means of piezometer monitorin g. Piezometer monitoring data can be analysed to ob tain the degree of consolidation of the improved marine clay. Back -analysis of the piezometer data will also enable t he coefficient of consolidation due to horizontal flow to be estimate d. Factors that affect the analysis of piezometers include period of assessment, hydrogeologic boundary condition, settl ement of piezometer tip and reduction of initial im posed load due to submergence effect. The aim of this paper is to hig hlight the significance and impact of the various f actors that affect assessment by the piezometer monitoring method.