Showing papers by "Arul Arulrajah published in 2008"

Characteristics of Singapore Marine Clay at Changi

Abstract: Singapore marine clay at Changi is a quartenary deposit that lies within valleys cut in the Old Alluvium. It is locally known as Kallang formation. The pre-reclamation site characterization and laboratory testing was carried out by conducting marine sampling boreholes, in situ dissipation tests and field vane test. In situ dissipation tests were conducted with the piezocone, flat dilatometer, self-boring pressuremeter and BAT permeameter. The purpose of the site characterization was to determine the consolidation characteristics, strength characteristics, stratigraphy, and mineralogy of Singapore marine clay. The consolidation properties of marine clay are required prior to land reclamation activities in order to predict the magnitude and rates of settlement with the expected fill load and future service load as well as for the design of soil improvement works. The shear strength properties are required for slope stability analyses during reclamation and for the stability analyses of shore protection works. Clay mineralogy tests and photographic identification of the marine clay was carried out to determine the mineralogical properties and to visually record the marine clay colour and texture.

Factors affecting consolidation related prediction of Singapore marine clay by observational methods

Abstract: The use of prefabricated vertical drains with preloading option is the most widely-used ground improvement method for the improvement of marine clays in land reclamation projects. The assessment of the degree of consolidation of the marine clay is of paramount importance prior to the removal of preload in such ground improvement projects. This analysis can be carried out by means of observational methods with the use of field settlement plates and piezometer monitoring. Field settlement monitoring data can be used to ascertain the settlement of the reclaimed fill from the time of initial installation. The field settlement data can be analysed by the Asaoka method to predict the ultimate settlement of the reclaimed land under the surcharge fill. Back-analysis of the field settlement data will enable the coefficient of consolidation due to horizontal flow to be closely estimated. Piezometer monitoring data can be analysed to obtain the degree of consolidation of the improved marine clay. Back-analysis of the piezometer data will also enable the coefficient of consolidation due to horizontal flow to be estimated. The aim of this paper is to highlight the significance and impact of the various factors that affect prediction by the Asaoka and piezometer assessment methods. The authors findings of the Asaoka method reveal that the magnitude of ultimate settlement decreases and the degree of consolidation subsequently increases as a longer period of assessment is used in the prediction. The degree of consolidation predicted by the piezometers is found to be in good agreement with the Asaoka method for the early period of assessment. However as the assessment period increases, the piezometer indicates lower degree of consolidation as compared to field settlement predictions.

Geotechnical testing to determine the suitability of biosolids for embankment fill

Abstract: Biosolids are an end product of municipal wastewater treatment and contain many of the constituents removed from the influent wastewater. The use of biosolids and other waste materials in a sustainable manner is currently being investigated in several countries around the world. A series of field tests were undertaken on biosolids stockpiles at Western Treatment Plant in Victoria. Following the field tests and sampling geotechnical laboratory tests were undertaken to assess the viability of using biosolids as fill material for embankment fills. Geotechnical properties of untreated biosolids and stabilised biosolids with 1%, 3% and 5% of cement were obtained from the laboratory tests. The field and laboratory test results were compared with the existing local road authority specification for fill material. INTRODUCTION The quantity of the municipal biosolids produced annually in the world has increased dramatically over the decades. Annually 66,700 dry tonnes of biosolids are produced from the 175 wastewater treatment plants in Victoria including 39,700 dry tonnes per annum biosolids from the Eastern and Western treatment plants in Melbourne which are managed by Melbourne Water Corporation (NRE, 2002). The Western Treatment Plant treats about 52% of Melbourne’s sewage where the sewage is mostly treated in vast lagoon systems. Sludge, which settles to the bottom of the lagoons, is pumped into a contained area where it dries to create biosolids. Biosolids by definition are treated sewage solids suitable for beneficial use in accordance with the relevant regulations whilst sludge is untreated sewage solids not suitable for use without further treatment In this project the engineering characteristics of biosolids at Western Treatment Plant (WTP) in Victoria, were investigated to assess the viability of using biosolids as fill material for embankment fill material. The engineering characteristics of biosolids have been reported previously by Hundal et al. (2005), Reinhart (2003) and O’Kelly (2005, 2006). The characteristics of the biosolids depend on various factors such as the type of waste, type of treatment process and age of the biosolids. In-situ geotechnical design parameters were obtained from the field tests. Geotechnical engineering properties of the untreated biosolids and cement stabilised biosolids with 1%, 3% and 5% cement were determined from laboratory tests. Field tests undertaken included Standard Penetration Tests (SPT) and field vane shear tests to determine the shear strength of biosolids. Laboratory tests were undertaken included compaction and California Bearing Ratio (CBR) tests. Geotechnical parameters for the biosolids were obtained from the field and laboratory tests and compared with the existing local road authority specification for fill material. FIELD TESTING OF BIOSOLIDS 1 PhD Candidate, Swinburne University of Technology, Melbourne, Australia 2 Senior Lecturer, Swinburne University of Technology, Melbourne, Australia 3 Lecturer, Swinburne University of Technology, Melbourne, Australia 4 Professor, Swinburne University of Technology, Melbourne, Australia

Case study of the Changi East Land Reclamation Project, Singapore

Abstract: Since the early 1990’s till early 2000s, the Changi East Reclamation Project in the Republic of Singapore involved the filling of approximately 200 million cubic meters of sand for the reclamation of a total land area of about 2500 hectares. The land reclamation works were carried out in 5 phases. The edges of the newly reclaimed land in the project were either retained by vertical retaining structure or coastal shore protection rock bund with suitable slopes and berms. Land reclamation was carried out using fill materials derived from dredging granular material from the seabed at the borrow source. Prefabricated vertical drains with surcharge were used extensively in the project to accelerate the consolidation process. In addition, deep sand compaction of the hydraulically placed sandfill was carried out by various deep compaction methods. Geotechnical instruments were required to monitor the settlement and pore pressure dissipation of the improved soft soil. During the implementation of the 5 phases of land reclamation and soil improvement projects, several thousand geotechnical instruments of various types were installed. In-situ testing of the marine clay was carried out prior to reclamation a well as after soil improvement. In-situ testing of the marine clay was carried out by means of field vane shear, self boring pressuremeter, cone penetration test and dilatometer tests. This paper provides a case study into the land reclamation, ground improvement, field instrumentation, in-situ testing and deep sand compaction works that were carried out in the Changi East Reclamation Project.

Application of Prefabricated Vertical Drains to the Changi Land Reclamation Project, Singapore

Abstract: The Changi East Reclamation Project in the Republic of Singapore involved the filling of approximately 200 million cubic of sand for the land reclamation of a total area of about 2500 hectares. Land reclamation was carried out using fill materials obtained from dredging granular material from the seabed at the borrow source. The ground improvement technique which involved combination of prefabricated vertical drain (PVD) with preloading was successfully applied in this project to improve the underlying compressible soils. The project comprises the installation of prefabricated vertical drains and the subsequent placement of surcharge to accelerate the consolidation of the underlying marine clay. In order to monitor the performance of ground improvement and to validate the performance of the prefabricated vertical drain system, several geotechnical instruments were installed to monitor the degree of consolidation at both area with PVD and area without PVD as control area. This paper provides a case study of the ground improvement works carried out with prefabricated vertical drains at the Changi East Reclamation Project and their subsequent performance assessment.