Research Publications

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Open Access
Computational Approach for Determining the Variation of Coefficient of Secondary Compression in Secondary Settlement Prediction of Soft Soils
(Sri Lanka Institute of Information Technology, 2023-03-25) Thilakarathne, T.M.D.; Vidurapriya, K.V.D.; Thilakasiri, H.S.
Secondary consolidation settlement takes place in soils after the completion of primary consolidation settlement, which is due to the dissipation of pore water pressure under the applied loads. The secondary settlement usually occurs due to the plastic adjustment of the soil particles and most commonly takes place in organic fine grained soils or soft soils. Hence, it is important to accurately estimate the secondary settlement in soft soils as the final stability of infrastructures built on soft soil grounds mainly depends on the amount of secondary settlement that takes place after the end of primary consolidation settlement. The coefficient of secondary compression (C) is a governing parameter in predicting the secondary settlement which is the slope of the consolidation curve for void ratio versus time. Also, various empirical correlations have been found by the past researches to find the value of the coefficient of secondary compression. In most of the instances, the secondary settlement is estimated by considering the coefficient of secondary compression as a constant value. However, the C value shows a variation with time and this could affect the secondary settlement estimation. Hence, it is necessary to investigate how the variation of coefficient of secondary compression affects the estimation of the secondary settlement in soft soils. In this study, the settlement data obtained from the Weligama Bay Marriot Resort and Spa project, Sri Lanka, is compared with the settlement values obtained from a computer generated programme. The progarmme simulates the settlement by considering the variation of the coefficient of secondary compression and by considering a constant coefficient of secondary compression value. The results show that the consideration of varying coefficient of secondary compression (with time) gives more accurate results than considering a constant coefficient of secondary compression in settlement prediction in soft soils.
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Consolidation settlement of vertically loaded pile groups in multilayered poroelastic soils
(Elsevier Ltd, 2023-01) Senjuntichai, T; Sornpakdee, N; Keawsawasvong, S; Phulsawat, B; Rajapakse, R.K.N.D.
Pile groups are commonly used as the foundations of many structures including those used in transportation infrastructures. Consolidation settlement of a pile foundation is an important design parameter. A theoretical model is developed in this study to estimate the consolidation settlement and axial load transfer of vertically loaded pile groups in multilayered poroelastic soils. The multilayered saturated soil is modeled according to Biot's poroelasticity theory. In order to determine quasi-static response of pile groups, the interaction problem is first formulated in the Laplace transform domain. Vertical displacement compatibility is enforced at the pile-soil interface to simulate the pile group-soil interaction. Axial deformation of each pile is represented by an exponential series with undetermined coefficients, which are obtained from a variational approach. Vertical displacement influence functions due to a buried uniform vertical load applied to the layered soil are required in the formulation. The application of an exact stiffness matrix method yields the required influence functions. Time-domain solutions are obtained by employing a numerical Laplace inversion method. Numerical results for time-dependent vertical stiffness and consolidation settlement are presented for different pile group configurations, layer profiles, pile elastic moduli and pile lengths.

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