Showing papers by "Arul Arulrajah published in 2009"

Ground improvement techniques for railway embankments

Abstract: A high-speed railway project for trains of speeds of up to 160 km/h is currently being constructed between Rawang and Bidor (110 km long) in Peninsular Malaysia. The ground improvement methods adopted in the project are vibro-replacement with stone columns, dry deep soil mixing (cement columns), geogrid-reinforced piled embankments with individual pile caps and removal/replacement works. This paper provides a detailed insight into the design and implementation of vibro-replacement and the deep soil mixing treatment methods used in the project. The use of plate bearing tests and field instrumentation to monitor the performance of the stone columns and soil mixing ground treatment methods is also discussed. This paper also provides a brief overview of other treatment methods implemented in this high-speed railway project such as a pile embankment with geogrids and removal/replacement works.

Soil improvement works for an offshore land reclamation

Abstract: The Changi East reclamation project was carried out in five phases along the foreshore of the east coast of Singapore. The water depths in the reclaimed area ranged from 5 to 15 m. The project involved hydraulic placement of 272 million m3 of sand onto soft seabed marine clay up to 50 m thick. A linear total of 170,000 km of prefabricated vertical drains (PVDs) were installed for accelerating the consolidation process of the underlying soft marine clay. The soil improvement works covered a total area of approximately 1200 ha. In this paper, the site conditions and the soil improvement works adopted are described. Pilot tests with full-scale field instrumentations as well as laboratory and in situ tests were carried out to verify the design, check the effectiveness of the soil improvement works using PVDs, and establish the most suitable drain spacing. Field monitoring data obtained from both the pilot tests and the reclamation works are presented and interpreted. Degree of consolidation was calculated bas...

Reclamation of a slurry pond in Singapore

Abstract: A case study for the reclamation of a slurry pond as part of an offshore reclamation project in Singapore is presented in this paper. The slurry pond covered an area of 180 ha. The slurry in the pond was recently deposited ultra-soft high-plasticity clay. The water content of the slurry was more than 120% and the undrained shear strength was less than 8 kPa. The reclamation was first carried out by spreading sand fill in thin layers 20 cm thick using a specially designed sand spreader. The filling speed was carefully controlled to allow the slurry to be consolidated before more fill could be placed. Despite the precautions a failure occurred, in the form of mud bursting. As a remedial measure, geotextile sheets were used to cover a total area of 630 000 m2 before more sand fill was placed. After the completion of fill placement, fill surcharge and prefabricated vertical drains (PVDs) were used to improve and accelerate the consolidation of the slurry. As the performance of PVDs would deteriorate after the...

Densification of granular soil by dynamic compaction

Abstract: Land reclamation often involves the placement of loose granular soil by means of hydraulic filling. Sand fill formed by hydraulic filling generally does not allow densification by surface compaction methods because of their limited depth of influence. Loose granular soil is susceptible to liquefaction upon the impact of dynamic forces. Even under static conditions, loose granular soil may be subjected to bearing capacity failure and large settlements, because of its low shearing resistance and high compressibility. Various densification methods are used for improving such soils to increase the friction angle and elastic modulus. Several methods of deep compaction are available for such applications; among these, dynamic compaction is one of the most effective ways of densifying granular soils to a significant depth. However, the success of dynamic compaction is affected by many factors, several of which are not yet fully understood. This paper deals with the dynamic compaction densification method utilise...

Instrumentation at Changi land reclamation project, Singapore

Abstract: Ground improvement is often required in land reclamation projects on soft soil deposits to reduce future settlement under the projected future dead and live loads. In the case of thick deposits of ...

Crushed brick blends with crushed concrete for pavement sub-base and drainage applications

Abstract: Demolition materials are generated by demolition ac tivities and account for a major proportion of the waste materials present in landfills Crushed brick and crushed con crete are major components of demolition materials Recycled crushed concrete, crushed brick and crushed rock ar e however viable substitute materials for natural r esources used as construction materials in engineering applications This paper presents the laboratory testing results of various proportions of crushed brick blends with crushed co ncrete The engineering properties obtained were co mpared with existing local authority specifications for pavemen t subbase and drainage systems to ascertain the pot ential use of crushed brick blends in these applications The dem olition materials for the experimental works were c ollected from a recycling site in Victoria, Australia

Geotechnical characteristics of recycled glass-biosolid mixtures

Abstract: The sustainable reuse of waste materials such as recycled glass (RG) and biosolids (Bio) in geotechnical applications would greatly reduce the demand for landfill sites and for virgin materials. The most important obstacle in the sustainable use of recycled glass and biosolids mixtures in geotechnical applications is the lack of knowledge about their engineering characteristics particularly when they are blended together. The use of such mixtures is a cost effective and innovative way of reusing both waste materials and overcoming the deficiencies that they would possess if they were used on their own. Preliminary tests were conducted on samples made of purely recycled glass and biosolids and also on blended RG-Bio samples to determine their geotechnical parameters. Particle size distribution, compaction tests and Direct Shear Tests (DST) were undertaken on both pure and blended materials. The shear strength characteristic of the mixture and its relation to the percentage of each component were analysed. It was concluded that the mixture takes advantage of the friction resistance of coarser recycled glass particles and the cohesion strength of finer particles which are mostly from biosolid grains. The results indicated that the RG-Bio mixtures have satisfactory shear strength characteristics which enable these mixtures to have an excellent potential to be used as an embankment fill material in roads. © 2009 IOS Press.

Stabilisation of biosolids with admixtures for potential use as an embankment fill material

Abstract: Biosolids are an end product of the wastewater trea tment process and contain many of the constituents removed from the influent wastewater. This paper is based on a proje ct currently implemented in Victoria to assess the viability of using biosolids as engineered fill material for road emba nkments. A series of geotechnical lab tests were co nducted to evaluate the engineering properties of biosolids samples ret rieved from Western Treatment Plant (WTP) in Victoria, Australia. The laboratory tests undertaken include particle de nsity, moisture content, organic content, Atterberg limits, particle-size distribution, proctor compaction, California Bearin g Ratio (CBR) and consolidation tests. Geotechnical laboratory tests were carried out on untreated biosolids as well as biosolids stabilised with 1%, 3% and 5% by weight o f cement and lime. The test results were subsequently compared w ith the existing local road authority specification for embankment fill material.

Shear strength behaviour of recycled glassbiosolids mixtures

Abstract: To enhance the shear strength properties of pure Fine Recycled Glass (FRG) and pure Biosolids (Bio), the innovative idea of blending these two materials was studied. The blended FRG-Bio material has the advantage of combining the high friction characteristics of recycled glass with the cohesive characteristics of biosolids. The Direct Shear Test results, California Bearing Ratio results along with other geotechnical test results indicated that 50FRG/50Bio, 60FRG/40Bio and 70FRG/30Bio blends provide a sufficiently high shear strength and friction angle for their usage as an embankment fill material. The findings showed the potential of blended recycled glass-biosolids to be used as a viable alternative to natural materials in road embankment applications. RÉSUMÉ Pour mettre en valeur les propriétés de résistance au cisaillement du Verre Recyclé Fin (VRF) pur et des Biosolides purs (Bio), l’idée novatrice de mélanger ces deux matériaux a été étudiée. Le mélange VRF-Bio a l’avantage de combiner les caractéristiques de haut frottement du verre recyclé et les propriétés de cohésion des biosolides. Les résultats de l’essai de cisaillement, les résultats de l’indice californien C.B.R et les résultats d’autres essais géotechniques indiquent que des mélanges 50VRF/50Bio, 60VRF/40Bio et 70VRF/30Bio fournissent une résistance au cisaillement et un angle de frottement suffisamment élevés pour être utilisés comme matériaux de remblayage pour les remblais. Les découvertes indiquent le potentiel d’utilisation des mélanges verre recyclé-biosolides comme alternative aux matériaux naturels dans les applications pour les remblais routiers.

In situ dissipation testing of soft soil under reclamation fills

Abstract: In situ dissipation tests provide a means of evaluating th e in situ coefficient of consolidation and hydraulic conduct ivity of soft clays due to horizontal flow. Dissipation t ests using piezocone (CPTU), dilatometer (DMT), self-boring pressuremeter (SBPT) and BAT permeameter (BAT) were utilized in the characterization of the coefficien t of horizontal consolidation and horizontal hydraulic conductivity of Singapore marine clay at Changi in a land recla mation project. Dissipation tests were carried out to compare the c hanges in the coefficient of consolidation and hydr aulic conductivity due to horizontal flow prior to reclamation and aft er ground improvement. Tests were carried out in a Vertical Drain Area as well as in an adjacent untreated Control Ar ea, 23 months after preloading for comparison purpo ses. The purpose of this research is to determine the consolidation parameters of soft soil before reclamation and afte r 23 months following preloading with and without vertical drai ns by means of in situ dissipation tests. This should indicate the change in these consolidation parameters associated with void ratio changes caused by the consolidatio n process under the same magnitude of load at different degrees of consolidation. The future expansion of Changi International Airpor t in Singapore, involves land reclamation next to t he existing airport. The offshore land reclamation is being carried out by the hydraulic filling of sand which is followed by the installation of vertical drains and subsequently surcharge place ment as a preload. As vertical drains are used to a ccelerate the consolidation of the marine clays, the permeability and consolidation properties of the soil particula rly in the horizontal flow are important design parameters. The determination of these design parameters is traditionally ba sed on the multiplier of coefficients of consolidation due to vertical flow, cv value obtained from the laboratory conventional consolidation tests. Results of these laboratory te sts however are usually subject to uncertainties pr imarily due to inevitable sample disturbances and uncertain multip lier values. Laboratory testing also does not yield appropriate properties of soil due to different loading and dra inage conditions as compared to the actual in situ condition. In situ dissipation tests are an alternative to traditiona l laboratory testing methods and furthermore the ef fect of disturbance to marine clays is minimal. These dissi pation tests can be conducted at various levels in the marine clay and hence variations of the coefficient of consolidatio n and hydraulic conductivity due to horizontal flow with depth can be studied. The last two decades have seen an emergence of in situ testing methods as an alternative to laboratory te sting methods. The in situ dissipation test has emerged as a useful method to obtain the required consolidation due to horizontal flow and permeability parameters for the design of vertical drain projects. Several types of in situ dissipation tests were adopted for the investigati on of the Singapore marine Clay at Changi. The dissipation tests were carried out with piezocone ( CPTU), dilatometer (DMT), self-boring pressuremeter (SBPT) and BAT permeameter (BAT) at an In Situ Test Site. The tests were carried out prior to rec lamation and 23 months after preloading. Tests were carried out in an area trea ted with vertical drains known as the “Vertical Dra in Area” as well as in an adjacent untreated “Control Area”. The tests were carried out to compare the change in consolida tion and hydraulic conductivity parameters at different degree of cons olidation stages under the same magnitude of load.