Study of dynamic pore water pressure and axial strain in saturated sand-gravel composites

By use of medium scale dynamic triaxial apparatus made by Earthquake Engineering Research Division,Dalian University of Technology,the development of axial strain and pore water pressure in sand-gravel composites during liquefaction is studied experimentally.At the same time,using DS-2T dynamic triaxial device scalping the oversized gravel particles and taking similar gradation method,a series of parallel tests proceeded.The development of shear strain and pore water pressure of sand-gravel composites and substituted material due to cyclic loading were compared.The results show that with isotropic consolidation,the development of dynamic pore water pressure in sand-gravel composites differs from that in substituted material and its curve can be fitted by corrected arcsine.However,the pore water pressure curve in substituted material can be fitted by arcsine function.The maximum value of dynamic pore water pressure in both of them can not reach the initial effective confining pressure.Also,the response of axial strain in sand-gravel composites is variant from that in substituted material and it increases steadily during cyclic stress action.The development in substituted material is not appreciable before initial liquefaction;when pore water pressure reaches its maximum value which is considered as the liquefaction standard,once initial liquefaction occurred.