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A. S. Balasubramaniam
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SELECTION OF SOFT CLAY PARAMETERS FOR BANGKOK LOWLAND DEVELOPMENT A. S. Balasubramaniam; S. R. Kim; D. G. Lirr; S. S. S. Acharya; T. H. Seah; D. T. Bergado
Lowland Technology International Vol 1 No 1, June (1999)
Publisher : International Association of Lowland Technology

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The paper stresses the importance of a sound understanding of the soil behaviour in both the limit equilibrium and numerical analysis in soil- structure interaction problems: deep foundation for tall buildings; foundation for elevated expressways, subways, ground improvements works, tunnels for water supply, natural gas supply, sewerage and drainage. In the limit equilibrium analysis the use of Hvorslev strength parameters is suggested while for lightly overconsolidated clays the strength to be referred as a frictional component. In the numerical analysis a realistic stress- strain model for the behaviour of soft clays for stress states below the state boundary surface is recommended.
EVALUATION OF THE PVD PERFORMANCE AT THE SECOND BANGKOK CHONBURI IDGHWAY (SBCH) PROJECT D. T. Bergado; A. S. Balasubramaniam; I. A. Chishtr; T. Ruenkrairergsa; Y. Taesiri
Lowland Technology International Vol 1 No 2, Dec (1999)
Publisher : International Association of Lowland Technology

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The soft Bangkok clay foundation at the Second Bangkok Chonburi Highway Project (SBCH) was improved using prefabricated vertical drains (PVD). Monitoring instruments such as surface settlement plates, deep settlement plates, inclinometers and piezometers were installed in the subsoil in order to observe the deformation behavior of the embankments under loading. The Department of Highways, Thailand, arranged for the monitoring and documentation of the deformation behavior. These monitored records, supplemented with the laboratory test results, were analyzed in order to verify the in-situ horizontal coefficient of consolidation of the soil as well as the rate and amount of settlement. The maximum surface settlement was calculated using one-dimensional consolidation theory, Skernpton-Bjerrurn method, as well as Asaoka's method. In addition, a one-dimensional FEM computer software, capable of calculating the consolidation of multi-layered soil, named PVD-SD was also used successfully to predict the rate and amount of settlement. Finally, the monitored deformation behavior was compared with the predictions during the design stage of SBCH to evaluate the performance of PVD. The amount of settlement predicted by Asaoka's method was in excellent agreement with the observed values, whereas the one-dimensional consolidation method, Skempton-Bjerrurn method and the PVD-SD FEM method showed some overprediction. The PVD performance at SBCH Project confirmed and validated the ground improvement by preloading and drainage on soft Bangkok clay.
THE APPLICATION OF NORMALITY RULE AND ENERGY BALANCE EQUATIONS FOR NORMALLY CONSOLIDATED CLAYS A. S. Balasubramaniam; E. Y. N. Oh; M. Bolton
Lowland Technology International Vol 7 No 1, June (2005)
Publisher : International Association of Lowland Technology

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In this paper, it is reiterated that the Roscoe and Poorooshasb (1963) formulation of the stress strain behaviour of normally consolidated clays is indeed in a more generalized form which is easily amenable to incorporate deformations under various degrees of drainage and can be extended to include cyclic loading and time effects beyond the primary phase of deformation. Also, the formulation can be used for stress states below the state boundary surface to include lightly overconsolidated and heavily overconsolidated clays. Particularly, it is shown here that Cam Clay model of Roscoe et al. (1963) and Modified Cam Clay model of Roscoe and Burland (1968) as based on energy balance equations and the normality concept can be considered as the special cases of the original formulation of Roscoe and Poorooshasb (1963). In order to achieve this, all theories are presented in similar mathematical forms, adopting the same formulation of Roscoe and Poorooshasb (1963). Modified Cam Clay Model of Roscoe and Burland, and the Roscoe and Poorooshasb theory made identical predictions of the shape of the state boundary surface, the pore pressure development during undrained behaviour, and the volumetric strain in the drained tests for all types of applied stress paths. Also, Modified Cam Clay model was only successful in predicting the shear strains along radial stress paths. For non-radial stress paths, Modified Cam Clay model needed an additional set of constant deviator stress yield loci, and when such a set was incorporated, the prediction from Modified Cam Clay model was the same as the original prediction of Roscoe and Poorooshasb (1963).
A MORE FUNDAMENTAL APPROACH TO PREDICT PORE PRESSURE FOR SOFT CLAY A. S. Balasubramaniam; E. Y. N. Oh; C. J. Lee; S. Handali; T. H. Seah
Lowland Technology International Vol 9 No 1, June (2007)
Publisher : International Association of Lowland Technology

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Skempton’s (1954) pore pressure coefficient A provides a pragmatic attempt at determining pore pressures during undrained shear, and to use these in settlement computations and stability analysis of embankments in soft clays. Also, the Critical state concept offers a means of acquiring the undrained stress path in normally consolidated clays through using a volumetric yield locus derived from a simple energy balance equation. However, to date there is no novel method by which the undrained stress paths of lightly over-consolidated and heavily overconsolidated clays can be predicted by using fundamental concepts. Based on the work of Handali (1986), Balasubramaniam et al. (1989) presented an alternative pore pressure coefficient that was more generalised than the Skempton’s coefficient. However, Pender (1978) proposed a set of parabolas to describe the undrained stress paths of overconsolidated clays, and Lee (1995) considered elliptic paths to be more in agreement with the experimental observations. In this paper, observed and predicted undrained stress paths both under compression and extension, and also from isotropic and K0 pre-shear consolidation states will be presented. Such expressions can then be readily used in computer softwares for stability analysis and settlement computations.
BORED AND DRIVEN PILE TESTING IN BANGKOK SUB-SOILS A. S. Balasubramaniam; E. Y. N. Oh; N. Phienwej
Lowland Technology International Vol 11 No 1, June (2009)
Publisher : International Association of Lowland Technology

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As a necessity to support an increasing magnitude of loads from tall buildings and long span bridges, the piling practice in the Bangkok Plain has moved several phases from driven pre-cast reinforced and pre-stressed concrete piles of smaller cross sections to spun piles and large diameter bored piles. The Chao Phraya plain in which the Bangkok city is located is low-lying and consists of a broad basin filled with sedimentary soils which form alternate layers of clay, sand, and clay. The upper clay layer is soft and highly compressible followed by a stiff clay layer extending to about 20 m or so and then followed by a layer of sand. Driven piles are normally taken down to this upper sand layer. However when the demand for a higher capacity arise, these piles cannot be extended in length due to construction problems and as such bored piles are needed to be taken down to as deep as 50 to 60 m. Below the upper clay layer there are eight interconnected aquifers from which ground water is pumped from deep wells. Thus in the design of piled foundations aspects such as the negative skin friction due to pile driving as well as deep well pumping are also needed to be considered. Some of the experiences gained over a period of 30 years in the study of piled foundations in the Bangkok Plain are briefly presented in this paper.
DISCUSSION ON “GEOTECHNICAL HAZARDS IN BANGKOK – PRESENT & FUTURE”, BY S. SHIBUYA, S. B. TAMRAKAR AND W. MANAKUL, LOWLAND TECHNOLOGY INTERNATIONAL, 5(1), 95-104 A. S. Balasubramaniam; N. Phienwej; D. T. Bergado; Y. N. Oh
Lowland Technology International Vol 6 No 1, June (2004)
Publisher : International Association of Lowland Technology

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The writers read with great interest the contribution on “Geotechnical Hazard in Bangkok – Present Future”. The writers had a long time interest in the subsidence of Bangkok since 1973 (see Piancharoen and Chuamthaisong, 1976; Piancharoen and Isarangula, 1974; Rammarong, 1974) or so.
Co-Authors C. J. Lee D. G. Lirr D. T. Bergado E. Y. N. Oh I. A. Chishtr M. Bolton N. Phienwej S. Handali S. R. Kim S. S. S. Acharya T. H. Seah T. Ruenkrairergsa Y. N. Oh Y. Taesiri