Research On The Law And Control Of Surface Settlement During Construction Of Metro Tunnel By CRD Method

With the acceleration of urbanization in China,the urban population is becoming more and more dense,and underground railways are being built on a large scale in major cities all over the country.Some difficulties and problems encountered in the process of subway construction need to be solved,and the surface subsidence problem has always been the focus of attention in the tunnel construction process.Because if the ground subsidence value is too large during tunnel excavation,it may lead to serious consequences such as ground collapse,tilt or even collapse of ground buildings and damage of existing underground pipelines,so it is particularly important to study the ground subsidence control.The research in this paper has important theoretical significance and application value for guiding the control of surface subsidence in subway tunnel construction.In this paper,based on the research background of a shallow-buried underground excavation section of a subway in Taiyuan,the surface settlement control of CRD tunnel construction is studied.The main contents of this paper are as follows:(1)This paper expounds the construction principle of shallow-buried and underground excavation method and its influencing factors on ground deformation,and summarizes the law of ground deformation caused by shallow-buried and underground excavation tunnel construction.(2)This paper introduces the engineering geological conditions around Taiyuan subway,the design of tunnel excavation and supporting structure,makes basic assumptions and simplifies the model through specific geological conditions,and obtains the surface settlement value through the three-dimensional finite element numerical calculation model.Based on the surface subsidence values on the longitudinal axis and cross section of the tunnel,the variation law of surface subsidence is analyzed,and then the actual monitoring values are compared with the simulated values to prove that the model is practical.(3)Aiming at the influencing factors of surface subsidence,the control of surface subsidence is studied.By reducing the removal length of temporary partition wall,the stiffness of advance support and the stiffness of initial support,it is found that reducing the removal length of temporary partition wall has a good effect on controlling surface subsidence,and it can be seen from the settlement curve that the final surface subsidence value is much lower than before.By increasing the stiffness of advance support and initial support,it can be intuitively seen from the settlement curve that both of them have no obvious effect on restraining surface settlement in the early stage of excavation,and with the progress of excavation,the reduction value of surface settlement gradually increases.Finally,it is found that increasing the stiffness of the initial support can effectively control the surface settlement,but only increasing the stiffness of the advanced support has a poor effect on restraining the surface settlement.It shows that only one measure can not achieve the control effect when controlling the surface subsidence,and a variety of control measures can be reasonably combined,which can not only achieve the purpose of controlling the surface subsidence but also save the engineering cost.Figure [62] table[7] reference [51]...