Calculation Of Surrounding Rock Pressure And Stability Analysis Of Surrounding Rock In Shallow Buried Bias Tunnel

With the rapid development of infrastructure construction in China,the mileage of expressways and high-speed railways has been rapidly improved.Due to China's vast territory and many types of topography and landforms,the lines often pass through tunnels when passing through mountainous and hilly areas.In the tunnel's import and export and some alongside mountain sections,shallow buried tunnels are easily formed.In the construction process,such tunnels often cause damage such as collapse of the surrounding rock,roof collapse,and cracking and bending of the supporting structure,which causes great damage and loss to the project.Therefore,it is of great significance to study the surrounding rock pressure and its stability under shallow buried bias conditions.In this paper,based on the failure mode proposed by the predecessors,the failure mode of the improved shallow-buried bias tunnel is given.The limit analysis upper bound method is used to deduct the perimeter without considering the bottom uplift and considering the bottom uplift factor.The calculation formula of rock pressure,and using MATLAB software to optimize the calculation formula,the final solution of surrounding rock pressure is obtained.The results obtained in this paper are compared with the existing literature results to verify the rationality of the method.On this basis,the effects of lateral pressure coefficient,bottom support coefficient,cohesion force,friction angle,buried depth and surface dip angle on surrounding rock pressure are analyzed.For the influence of different construction methods and excavation steps on surrounding rock stress and displacement stability during tunnel construction,this paper uses the shallow buried section of the Yanbian tunnel as the engineering background,and establishes a three-dimensional numerical model through ABAQUS software.Excavation simulation was carried out to study the deformation and stress variation of surrounding rock under different working methods,and the supporting structure was compared and analyzed.The results show that during the tunnel construction process,the phenomenon of bulging at the bottom of the tunnel is obvious,and uneven settlement occurs on the deep and shallow buried sides of the tunnel.The whole tunnel is affected by the bias load.Dueto the asymmetric deformation on both sides of the tunnel,the stress release difference of the surrounding rock in the deep and shallow buried side causes the deflection of the stress field trace of the tunnel surrounding rock.Comparing the displacement field,stress field,plastic zone and supporting structure under three kinds of construction methods,it can be seen that the cross-intermediate wall method has the best control effect on the stability of the tunnel,followed by the single-wall guide pit method,and the three-step temporary inversion method.Worst.This paper can provide some reference for related engineering practice in the study of surrounding rock pressure calculation and surrounding rock stability analysis.