Numerical Simulation And Deformation Monitoring Of A Shallow-Buried Underground Tunnel Construction In Harbin

In recent years,as the country's infrastructure construction to increase,the urban subway system has been developed rapidly,and the shallow excavation method has been widely used in subway tunnel construction.In cities,the population distribution is more dense,and the distribution of ground buildings and underground pipelines is complex.Under such conditions,the construction of shallow tunnels will inevitably cause disturbance to the surrounding rock and soil and cause the formation deformation.If the deformation exceeds a certain limit,it will be inevitable Which threatens the safety of ground structures,urban traffic and underground pipeline facilities.Therefore,it is of great practical significance to study and reasonably control the formation deformation caused by subway tunnel construction.This article takes the Xianghui interval tunnel of Harbin Metro Line 3 as the engineering background,and uses the finite element analysis software of MIDAS/GTS to carry out the numerical simulation of the construction process.Firstly,through simulation,it is concluded that when the tunnel face reaches approximately2.5 times the diameter of the tunnel before the monitoring section,the monitoring point begins to deform;The deformation of each monitoring point tends to be stable when the palm surface is about 2.5 times tunnel diameter after the monitoring section;When the face of the face is approximately 1 times the diameter of the tunnel before and after the monitoring section,the deformation growth rate of each monitoring point is faster,and the amount of deformation generated increases sharply.When the excavation face is in this stage during construction,it should be cautious.Construction and enhanced monitoring.Secondly,through the comparison between the numerical simulation results and actual field monitoring data,it is concluded that the deformation of the tunnel dome sinking and the tunnel clearance convergence is mainly caused by the excavation of the upper step,when the monitoring point is buried for about 10 days.The deformation is large in time,and as the excavation time advances,the deformation rate decreases until the deformation becomes stable;The surface settlement curve of the ground generally agrees with the Peck formula.The increase of the settlement rate and deformation amount mainly occurs at the section of the excavation surface that passes through the monitoring section.The settlement generated in this section accounts for about 60% of the total settlement;The vertical settlement of the ground surface can be divided into four stages according to the distance between the excavation surface and the monitoring section.They are: small settlement stage,rapid settlement increase stage,slow settlement stage,settlement stabilization stage,and thedistance between the excavation surface and the monitoring section is from-1D to 3D.The scope is the main section that controls the surface settlement;The surface subsidence trough of the double line tunnel is similar to the superposition of the surface subsidence curve generated by a single tunnel,and is in the form of "single peak".Finally,the double line tunnel construction causes the surface subsidence are simulated,and the factors affecting the draw: tunnel during the construction of the up and down the steps to reserve core making,reduce the reserved length on the steps,before the construction of the tunnel arch position forepole,increase the depth of the tunnel can be effectively reducing surface subsidence caused by tunnel during excavation.