Dynamic behavior and characteristic failure response of low plasticity cohesive soil
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RESEARCH PAPER
Dynamic behavior and characteristic failure response of low plasticity cohesive soil Adarsh Singh Thakur1 • Saloni Pandya2 • Ajanta Sachan1 Received: 21 May 2020 / Revised: 30 July 2020 / Accepted: 11 August 2020 Ó Iran University of Science and Technology 2020
Abstract The present study evaluates the effect of stress history and loading conditions on dynamic behavior and failure characteristics of low plasticity cohesive soil. A series of two-way strain controlled cyclic triaxial tests were performed on soil samples collected from seismically active region of Gujarat (India). The effect of stress history and loading conditions on low plasticity soil was evaluated for OCR values of 1–4 and cyclic axial strain amplitude (ea ) variation of 0.5%, 1%, 1.5%, and 2%, respectively. The low plasticity soil was observed to undergo liquefaction even at lower amplitude and higher OCR. Liquefaction resistance of soil was observed to increase with the increasing OCR (1–4) and decrease with the increment in cyclic strain amplitude (0.5%—2.0%). The rate of stiffness degradation exhibited bilinear response when pore pressure ratio (ru) was observed to be 0.85. This indicated the generation of cyclic instability prior to flow liquefaction in low plasticity cohesive soil. Two-staged failure response was observed due to the subsequent transition from cyclic instability behavior to flow liquefaction. The low plasticity cohesive soil was found to experience first ‘clay-like behaviour’ due to commencement of cyclic instability and then ‘sand-like behaviour’ due to initiation of flow liquefaction. The low plasticity cohesive soil was observed to experience cyclic instability between 0.85 \ ru \ 0.95, and then, flow liquefaction at ru [ 0.95. Keywords Liquefaction Cyclic instability OCR Cyclic strain amplitude Dynamic response Stiffness degradation rate Low plasticity soil List of PI GSD OMC MDD LL OCR ASHL SHL CL ML d
symbols Plasticity Index Grain size distribution Optimum moisture content Maximum dry density Liquid limit Over-consolidation ratio Asymmetrical hysteresis loop Symmetrical hysteresis loop Clay of low plasticity Silt Cyclic stiffness degradation index
& Ajanta Sachan [email protected] Adarsh Singh Thakur [email protected] Saloni Pandya [email protected] 1
IIT Gandhinagar, Palaj, Gandhinagar, Gujarat, India
2
Navrachana University, Vadodara, Gujarat, India
ru G D Ga Da rd rdmax Du ea m Esec Esec,a N NL ev Drc’ W DWT t1 t2
Pore water pressure ratio Shear modulus using SHL Damping ratio using SHL Shear modulus using ASHL Damping ratio using ASHL Deviatoric stress Maximum deviatoric stress Excess pore water pressure Cyclic axial strain amplitude Poisson’s ratio Dynamic Young’s modulus using SHL Dynamic Young’s modulus using ASHL Number of cycles Number of cycles to attain liquefaction Volumetric strain Effective confining pressure Energy dissipation in single cycle Total energy dissipated Degradation parameter for bilinear response Degrad
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