Pore pressure-shear strain relationship of saturated sand based on in-situ liquefaction tests

Based on the self-developed in-situ liquefaction testing technology, two different types of in-situ liquefaction tests were carried out. The pore pressure-shear strain relationship of saturated sand was studied and its quantitative expression was presented. Besides, the simulation results were compared with the dynamic triaxial test results and the in-situ liquefaction test results by others. The main conclusions are as follows. The acceleration slightly affects the pore pressure-shear strain relationship of saturated sand, but its influence is larger than that of the relative density. An equation, [U=1-exp(aγ+b), U≥0], Which is consistent with the mathematical expression of the physical process of soil liquefaction, was proposed to quantitatively describe this relationship. When the shear strain of saturated sand is at the range of 0.03%~0.30%, the residual pore pressure increases quickly. Furthermore, when the shear strain of saturated sand is about 0.5%, the residual pore pressure ratio can reach the maximum value 1. These results are consistent with those obtained from strain-controlled dynamic triaxial tests by Dobry, but have discrepancy with these obtained from in-situ liquefaction tests by Chang. The unexpected results were analyzed and it is found the discrepancy is caused by the unadapted computation method for shear strain adopted by Chang. In the process of soil liquefaction, large deformation occurs, and it is unreliable to calculate the shear strain by the finite element method. © 2018, Editorial Office of Journal of Vibration and Shock. All right reserved.