Browsing by Author "Premkumar, S"

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    item: Conference-Abstract
    Evaluation of liquefaction potential of Western and Eastern Coastal Areas in Sri Lanka
    Premkumar, S; De Silva, LIN
    There has been an increasing concern on earthquake related disasters in Sri Lanka after 2004 tsunami. It is partly due to the fact that that most of the important structures in Sri Lanka are founded on loose sandy soils along the coastal areas. During a strong earthquake, there is a huge possibility that these loose sand deposits may liquefy causing significant damage to the structures founded on them. In addition, some of the coastal areas suffer frequent floods, which may magnify the damage due to liquefaction. Standard Penetration Test (SPT) and Cone Penetration Test (CPT) are widely used for the site specific evaluation of liquefaction potential of sandy soils. In this paper, results of the analysis of liquefaction potential based on SPT resistance values are presented. Here, 46 bore holes from Colombo and east- coast were analyzed, and the liquefaction potential was evaluated by means of a factor of safety against different earthquake magnitudes and different ground water levels. From the analysis results, liquefiable areas and the depths of liquefiable areas were identified. It was observed from the analysis of 24 boreholes in Colombo area that, 3-13 m depths from ground surface are liquefiable during a 6.5 magnitude earthquake, while on average 4-10 m depths are liquefiable in Batticaloa, Mutur, and Ampara areas in the east coast under normal ground water conditions.
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    item: Conference-Full-text
    Framework for the estimation of overall probability of dam failure of ancient earth dams in Sri Lanka.
    (Department of Civil Engineering, University of Moratuwa, 2011-12) De Silva, LIN; Premkumar, S; Ratnayake, N
    Sri Lanka has a rich history of earth dam construction with over 300 large scale ancient earth dams in service, However, large number of ancient earth dams are suffering partial falier due to excessive seepage, piping and slope instability. The failure of an earth dam involves a probability of falier and therefore the individual probabilties estimated for different falier modes under various loading condition need to be combined The probability of failure tor each mode ,involves engineering assessment of the particular failure mechantsms. and looking for solutions that can reduce the probability of those falier modes or minimise the consequences of a failure. No standard framework is adopted in Sri Lanka for the estimation of overall probability of dam failure The objective of this paper is to develop a standard framework for the estimation of over orall probability of dam failure to be included in the quantitative risk assessment process for ancient earth dams in Sri Lanka. Critical loading conditions which are relevant to Sri Lanka are considered in the present study.
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    item: Conference-Extended-Abstract
    Liquefaction potential of sand deposits in Sri Lanka
    (2010) De Silva, LIN; Premkumar, S; Sujeevan, N; Nainanayaka, NPARK
    After 2004 tsunami, the frequency of earthquake occurrence near Sri Lanka has increased significantly. On the other hand. it should be noted that most of the important structures in Sri Lanka are founded on sandy soils along the coastal line. During a strong earthquake. there is a high risk that these sand deposits may liquefy causing significant damage to the structures founded on sandy soils. Standard Penetration Test (SPT) and Cone Penetration Test (CPT) are widely used for the site specific evaluation of liquefaction potential of sandy soils. In this paper, results of SPT-based liquefaction potential evaluation are presented. Mere. 46 hare holes front Colombo and east- coast were analyzed, and the liquefaction potential was evaluated by means of a factor of safety against different earthquake magnitudes, front the analysis results, liquefiable areas and its depths were identified. It was observed from the analysis of 46 boreholes, that 3-12 m depths from ground surface are liquefiable in Colombo area during a 6.5 magnitude earthquake, while on average 4-10 m depths are liquefiable in Batticaloa. Mutur and Ampara areas in the east coast.