Study On The Influence Of The Roadbed's Deformation Of Highway Caused By The Construction Of Undercrossing Tunnel

Tunnel as a very important traffic structure,is widely applied in the construction of high-speed railway and highway.In order to save the land,protect existing buildings and environment,undercrossing tunnel is applied.The tunnel underpassing the existing highway has become popular in recent years,the top cover layer of the tunnel is thin,the wall rock is poor in stability and is easy to deform even fail,which seriously affect the construction of tunnel and the safety of the highway.Therefore,tunnel construction has important significance on the impact of highway roadbed deformation.The construction of the railway tunnel undercrossing an existing highway in Guizhou Province is taken as the background of this study in this paper.Through numerical simulation,field monitoring,theoretical analysis,the influence of the roadbed's deformation of highway caused by the construction of undercrossing tunnel is studied.The main research work is as follows:(1)Using FLAC3D to simulate the process of field construction,analysis of tunnel excavation process and the relationship between deformation of the subgrade,the deformation law of roadbed excavation: greater depth of highway roadbed settlement influence scope deformation is bigger,the effect of longitudinal depth is generally more than the excavation depth of excavation,transverse influenced range increases gradually with the increase of the tunnel depth,the maximum effect of position for the tunnel axis,the maximum width is about5 times the tunnel span.The CRD construction method can effectively control the subgrade settlement of highway subgrade,the cumulative settlement is 36.6mm,less than the standard40 m M.,a cross section of roadbed and tunnel deformation rate with the distance of the tunnel face increases,reaching the section on the tunnel face when the sedimentation rate increases quickly,away from the section settlement rate quickly stabilized.(2)Were analyzed using field monitoring of tunnel under subgrade deformation,variation of subgrade caused by tunnel construction that the settlement of highway subgrade and the lateral sliding variation: CRD construction method has little effect on the top of highway roadbed subsidence,the maximum not more than 35 mm,to meet the design standards of 40 mm tunnel;for the construction of highway subgrade deformation level was less affected.The settlement of highway pavement deformation respectively through advanced uplift stage or small subsidence stage,rapid settlement deformation stage,slow subsidence deformation stage,stable subsidence stage.The results of numerical simulation and field monitoring.The reliability of the numerical simulation is verified by the small difference.(3)Linear M-C yield criterion and the limit analysis upper bound method based on theestablishment of the face because of instability failure mode of highway subgrade instability,derive the upper bound expressions of the tunnel under the critical depth,and the use of nonlinear programming program optimization calculation of the critical solution,analyze the influence of various factors on the law and the impact of critical burying deep.