Study on dynamic pore water pressure in silty clay interbedded with fine sand of Nanjing

The interbedded strata of silty clay and fine sand in Nanjing is a sediment deposited alternately by silty clay and fine sand with its appearance as a " thousand layers cake".Nanjing fine sand mainly consists of schistous grains and is different from the standard sand with round quartz grains. Nanjing fine sand is anisotropic because of the schistous grain. By use of DSZ-1 dynamic triaxial apparatus made by Nanjing University of Technology, Nanjing silty clay interbedded with fine sand and Nanjing fine sand were tested. Through the analysis of these test results, the following conclusions are drawn.First, with isotropic consolidation, the development of dynamic pore water pressure in silty clay differs from that in fine sand because of the particular structure of interbedded with silty clay and fine sand and its curve can be fitted by hyperbola. However,the pore water pressure curve in fine sand is same as that advanced by Seed and can be fitted by arcsine function. Second, with anisotropic consolidation, there is similar development of dynamic pore water pressure in these two soils. Both of them can be fitted by hyperbola.Finally, whether in isotropic consolidation or in anisotropic consolidation, dynamic pore water pressure can not approach confining pressure when axial strain 5% is considered as the liquefaction standard of the interbedded strata of silty clay and fine sand .