The shear modulus of soil is one of the primary mechanical indicators for quality check in ground treatment.The liquefaction of saturated sand ground may occur during earthquake,which results in the decrease of the soil stiffness and the ground bearing capacity.With excess pore water pressure gradually dissipating and effective stress increasing,the soil stiffness gradually recovers to the pre-earthquake level.The degradation of soil stiffness during soil liquefaction is of great importance to understand the dynamic responses of the liquefiable ground,as well as the bearing capacity and deformations of the ground.However,it is difficult to monitor the soil stiffness during shaking directly in engineering practice.In this study,based on the effective stress mechanism and Hardin's equation,the prediction method of small-strain shear modulus of the saturated sand during cyclic loading was proposed.Centrifugal model test of inclined sand slope was carried out to monitor the acceleration,excess pore water pressure and settlement of the model ground during shaking.In addition,the piezoelectric bender element system and high-speed camera were used jointly to collect the triggering and receiving shear wave signals during shaking.The shear wave velocities at different moments were processed by video recognition technique.The test results show that the predicted shear wave velocity is in agreement with the measurements of piezoelectric bender elements.They both tell the fact that the small-strain shear modulus of saturated sand decreases with the accumulation of excess pore water pressure during shaking,and gradually recoveres with the dissipation of excess pore water pressure after shaking.This study provides a scientific basis for monitoring and detecting the stiffness of saturated soft soil foundations under seismic loading.
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