Experimental Study On Dynamic Parameters Of Frozen Silt Soil In Heilongjiang Province

With the expansion of China's development strategy,the construction of projects in cold regions is increasing day by day.The dynamic performance of soil in seasonal frozen regions has seriously restricted the development process and needs to be solved urgently.At present,there are many disputes in the research of seasonal frozen soil,and the development level of instrument and test technology are limited,which need to be further explored.In this paper,the effects of negative temperature,freeze-thaw times,initial moisture content,confining pressure and vibration frequency on dynamic modulus and damping ratio of frozen silty sand are studied by means of GDS dynamic triaxial test.The correction coefficients and calculation formulas of initial dynamic modulus and maximum damping ratio are proposed.The envelope curves and normalized curves of dynamic modulus ratio and damping ratio are given.The main work is as follows:(1)The basic physical properties of soil samples are comprehensively analyzed by water content,density,specific gravity,particle analysis and compaction test,and the main physical parameters are obtained.(2)The influence of negative temperature on the dynamic properties of silty sand is studied,and the changing rules of various dynamic parameters are obtained.The temperature correction coefficient and calculation model of initial dynamic modulus and maximum damping ratio are proposed,and the envelope of dynamic modulus ratio and damping ratio in a certain temperature range is given.The results show that the negative temperature has a great influence on the initial dynamic modulus and damping ratio,but a little influence on the dynamic modulus ratio and the maximum damping ratio.(3)The effects of freeze-thaw times on the dynamic properties of silty sand are studied,and the variation laws of various dynamic parameters are obtained.The correction coefficients and calculation models of freeze-thaw times of initial dynamic modulus and maximum damping ratio are proposed,and the envelopes of dynamic modulus ratio and damping ratio in the corresponding range of freeze-thaw times aregiven.The results show that the number of freeze-thaw cycles has a greater impact on the initial dynamic modulus and a smaller impact on the maximum damping ratio.The first five freeze-thaw cycles have a significant impact on the dynamic modulus ratio and the damping ratio,and tend to be stable after five freeze-thaw cycles.(4)By studying the dynamic properties of silty sand with different initial moisture content,confining pressure and vibration frequency,the influencing rules and range of relevant parameters are obtained.The results show that the optimal moisture content has a great influence on the initial dynamic modulus;confining pressure has a great influence on the damping ratio,but has a little influence on the dynamic modulus ratio and the initial dynamic modulus;vibration frequency has little effect on the dynamic modulus ratio,but has a prominent effect on the damping ratio.The normalized curves and calculation models of dynamic modulus ratio and damping ratio under different conditions are given.