| With the rapid development of urban rail transit,earth pressure balance shield tunnel construction technology is more and more used in the construction of subway tunnels.The excavation of shield tunnel will cause unloading deformation of surrounding soil.The degree of deformation is affected by many factors,such as palm face thrust,synchronous grouting pressure,surrounding stratum conditions,load and so on.In the actual construction process,cave-in,segment floating,surface subsidence,water gushing and mud gushing are easy to occur.Therefore,it is very important to study the unloading deformation characteristics of the soil around the shield tunnel and reveal the deformation process and law of the soil around the tunnel during shield tunneling.The research results have certain theoretical significance and great application value for maintaining the stability of the stratum and preventing and mitigating disasters during the construction of the shield tunnel.Based on the analysis of the measured data of surface settlement,the development process and law of surface settlement and deformation during shield tunneling were studied.Combining with the three-dimensional numerical analysis method,the deformation characteristics of soil around the construction of single-track and doubletrack tunnels and the deformation law of soil with different influencing factors were explored,which can provide guidance for the construction of field projects.The main conclusions of this paper are as follows:(1)Based on large-scale three-dimensional loading test system and self-designed micro non-contact displacement measurement system,large-scale indoor model tests with similar shrinkage ratio of 1:30 were carried out,and the unloading deformation law of soil around the tunnel during excavation was obtained.By simulating different soil loss rates and loading conditions,the influence law of the unloading deformation on soil around the tunnel and surface soil was obtained.(2)Relying on the Yaozhuang~Wenboyuan station of Xuzhou Rail Transit Line 2,the spatial and temporal distribution and development of surface soil settlement and deformation during site construction were obtained,as well as the disturbance law of surface settlement and deformation during the construction of double-track tunnel.(3)Using ABAQUS finite element software and based on the general situation of Yao-Wen section project,a three-dimensional shield tunnel excavation model was established.By assuming different constitutive models of surrounding soil,a constitutive model which can characterize the deformation characteristics of clay in Xuzhou area was obtained.By changing the grouting pressure and the propulsive force of the face,the influence on the deformation law of soil around shield tunnel excavation and the mutual disturbance mechanism of single-track and double-track tunnel excavation were obtained.(4)The reliability of the research method was verified by comparing the results of laboratory test,field measurement and numerical calculation,and the disastercausing mechanism was studied through the analysis of three-dimensional deformation history nephogram of the soil around the tunnel. |
PDF Full Text Request