Post-cyclic volumetric strain of calcareous sand using hollow cylindrical torsional shear tests

摘要

Post-cyclic settlement of saturated soil, due to dynamic loadings such as earthquake, causes severe damage to structures. Dissipation of excess pore water pressure generated during cyclic loadings results in the volumetric strain of soil materials. Many studies have been conducted on factors affecting post-cyclic volumetric strain (epsilon(re)(,v)) of siliceous soils. The effect of important factors on post-cyclic settlement of calcareous sand is evaluated in this study. Calcareous soils are generally located in tropical and subtropical areas near oceans and gulfs. These deposits are usually saturated and consequently, post-cyclic settlement can be critical in these sediments. In this research, a series of hollow cylindrical torsional shear tests were performed on Hormuz calcareous sands obtained from the north coast of the Persian Gulf. The samples were loaded cyclically under different cyclic stress ratios (CSRs) in undrained condition and then, terminated at a desired pore water pressure ratio (r(u)). After that, the excess pore water pressure was allowed to dissipate, and volumetric strain occurred as a result. The effects of relative density (Dr), cyclic stress ratio (CSR), excess pore water pressure ratio (r(u)) and maximum cyclic-induced shear strain (gamma(max)) on epsilon(re)(,v) of the reconstituted sand were evaluated. The results showed that maximum shear strain is the most effective factor in estimating the post-cyclic settlement of the calcareous sand.