Study On The Deformation Law Of Soft Clay Under Dynamic Load Of Urban Metro

With the rapid development of the economy and technology,the level of urbanization is getting higher and higher in China.The growth of urban population has led to a sharply increase in urban passenger traffic volume.The construction of large-capacity and fast metro transportation is an effective way to alleviate urban traffic congestion.The soft soil layer is widely distributed in China,and the monitoring data of metro projects in operation reveals that the soft clay soil foundation will settle under the action of dynamic load,which affects the safe operation of the metro.In order to study the settlement characteristics of soft clay under the action of dynamic load,the settlement deformation of the section from Fanghua Road to Longyang Road of Shanghai Metro Line 7 is taken as an engineering case,and the research is as follows: First,according to the characteristics of the force and deformation of the metro under the dynamic load of the soft clay foundation,a set of test equipment is designed to simulate the deformation of the tunnel under dynamic load.Through the indoor model test,the deformation of the soft clay foundation under the dynamic load is obtained.Then based on the finite element software Midas GTS NX,a three-dimensional dynamic finite element model was established,the soft clay under the normal design speed(80 km/h)and the high-speed(120 km/h)was compared and analyzed.Combined with indoor model test results and empirical formulas,the subsidence of the metro after many years of operation is predicted.Finally,according to the results of on-site monitoring and numerical simulation data,the model is revised.The research results show that the higher the train speed,the greater the deformation of the tunnel foundation soil,and the larger the lateral influence range of the surface settlement trough,but the settlement decreases with the increase of the metro speed.The settlement of the metro line after one year of operation is about 45 mm,and the settlement after 20 years is about 58 mm.The growth rate of the settlement prediction curve decreases gradually,and the settlement increment is very small for a long time in the later period of operation.By comparing the settlement data monitored on site,the error of the research results in this paper is within a reasonable range.It verifies the reliability of model tests and numerical simulations to a certain extent,and also provides guidance for the safe operation of metro on soft clay foundations.