Research Of Dynamic Properties Changes And Microscopic Mechanism Of Aging Sand

Soil dynamic shear modulus and damping ratio are the most important dynamic characteristic parameters, are indispensable dynamic parameters to the soil and foundation seismic response analysis, and also the essential content in the site seismic safety evaluation. Fourteen tests of Fujian standard sand under different conditions using British GDS resonant column (RCA) system was conducted with the aim of researching the aging effects on small-strain shear modulus and damping ratio of sands and give explanations for the test results based on grain slip and contact force homogenization theory of granular materials. The experimental results show that, within a certain confining pressure, small-strain shear modulus gradually increases with time and, the damping ratio decrease gradually with time. At the same time, the research founds that the relative density, stress history and fines contents significantly effect the aging of sand. Under the confining pressure of35kPa, time effects of loose sand is greater than dense sand, however, when the confining pressure increase to150kPa, time effects of loose sand is less than dense sand. Stress history is one of the important factors affecting time effects of sand:unloading-reloading cycles and overconsolidation both can reduce the growth rate of small-strain dynamic shear modulus of sand. Aging rate of sand will be increased if dry kaoline powder was added to samples.