Experimental Study On Dynamic Characteristics Of Cohesive Soil Under Subway Moving Loads

By the end of 2016,more than 30 cities had opened subway traffic operations with the length of 3168.6 km in China.At present,there are 11 planed subway lines with the length of 400 km in Shenyang,and the Metro Line 1 and 2 with the length of 55.07 km have been officially put into operation,and the new 5 Metro Lines have been built with the length of 186 km.With the massive construction of subway,there are more and more engineering problems during the operation of subway,such as the uneven settlement of soil around the tunnel which leads the structure of tunnel to sink.Although this study have been carried out in some areas which achieved some achievements,but the soil has great constitutive property and spatial variability,this achievements can not accurately evaluate the dynamic characteristics of soil under subway moving loads in Shenyang area,and the research of theoretical and practice on the dynamic characteristics of soil under subway loading is less in Shenyang area.Under this background,this paper was carried out with the supported by the Experimental Study on Dynamic Characteristics of Cohesive Soil Under Subway Moving Loads in Shenyang Area,taken the Metro Line 9 as the engineering background and taken the undisturbed silty clay as subjects in the study,based on the characteristics of subway moving loads,and was carried out the dynamic triaxial test and resonance column test to cohesive soil around the tunnel in Shenyang area,and study on the dynamic characteristics of cohesive soil under subway moving loads.Main contents are as follows:(1)By laboratory routine tests,the basic physical parameters of silty clay around the tunnel in Shenyang area were setting-out,which provided a fundamental basis for the parameters of dynamic triaxial test and resonance column test;(2)Through dynamic triaxial test,this paper explores the law of development of three kinds of silty clay of the accumulated plastic strain and pore pressure under different conditions,and the influence with confining pressure,consolidation ratio,dynamic stress amplitude and frequency to accumulated plastic strain and pore pressure;(3)On the basis of understanding the law of development of the accumulated plastic strain and pore pressure.Through the orthogonal experimental design,this paper uses mathematical statistics to calculate the influence ratio of the accumulated plastic strain and pore pressure with the confining pressure,dynamic stress amplitude,frequency,vibration frequency and their coupling;(4)Based on the existing models and through the comparison of models,this paper builds the model of accumulated plastic strain and pore pressure which is suitable for Shenyang area and determines the specific parameters of the model;(5)Based on the above research,through the GDS resonant column test,the variation of dynamic shear modulus and damping ratio of three kinds of silty clay under different confining pressure test conditions are discussed in detail.The research of this paper has important guiding significance for the design,construction and safety and stability evaluation of underground rail transit in Shenyang.