Study On Mechanism And Prevention Of Surface Collapse Induced By Urban Subway Tunnel

With the rapid development of China's subway construction in recent years,a large number of subway tunnel structures are formed in the urban commercial economic region,which makes the adjacent buildings around the subway tunnel have a large number of structures,large spatial interlacing effects,and complex structures and basic forms.The collapse of the surface induced by subway tunnel construction threatens the safety of surrounding buildings.It can easily cause serious economic losses.Therefore,it is an non-negligible question that how to ensure the stability of the subway tunnel construction process.Subway construction causes the collapse of the surface is affected by many factors which are prettycomplex.The difference in the mechanism of subway tunnel construction induced the collapse of the ground and it has a great distinction.The article is based on Shengyang Metro Project.We use elastoplastic mechanics,similarity theory,Peck sedimentation theory,regression analysis and numerical calculation software FLAC3D to study the mechanism and prevention of surface collapse.The combination of theoretical analysis,similar model test,on-site detection and numerical calculation is also used in the study of the mechanism of instability of surface collapse.The mechanism analysis of the surface collapse induced by subway tunnel construction was analyzed,and the ground settlement law caused by different excavation methods of subway tunnel was studied.The main research contents of this paper are as follows:(1)The engineering is based on Shenyang Metro.We produced a scale model with a 1:50 similarity ratio.We conducted an excavation test of a similar model of a subway tunnel.The experimental data is compared with the measured engineering data,and the correctness of the modified Peck formula coefficients is verified.(2)The study is based on the FLAC3D three-dimensional numerical model.We study the law of surface settlement and deformation caused by CRD method,step method and shield method in subway tunnel excavation.We analysis of surface settlement and stress distribution of tunnel structures.The vertical displacement of the cross-section of the stratum caused by the three methods is symmetrically distributed.The surface generated by the CRD method is with the largest final settlement and the shield method is the smallest.During the tunnel excavation process,the principal stress of the tunnel of the CRD method is first stabilized.The shield method and the upper and lower steps are second.(3)We study the correspondence between the measured value and the distance of the measuring point from the tunnel axis.Based on the Peck formula,the regression analysis is used to perform linear regression analysis on the measured data.The lnS(x)after regression and the original measured values are compared.We compare the settlement curve after regression with the prediction curve of Peck formula.It is found that the curve after regression can better show the law of sedimentation.And it meets the distribution law of the measured points.The maximum settlement correction coefficient a suitable for a certain area is obtained.The maximum distribution correction parameter a of the surface is mainly concentrated in 0.3?0.7,accounting for 75%of all numerical distributions.It can correct the maximum settlement value of the surface.According to the settlement curve after regression,we also analyze the interval distribution of ?.The ? distribution interval is mainly concentrated in 0.4?0.9,accounting for 92.75%of all numerical distributions.It can better correct the settlement tank.The paper has 126 pictures,30 tables,and 125 references.