Study On The Mechanism And Control Measures Of Large Deformation Of Soft Rock In Xincun Tunnel

In the process of large-scale tunnel construction today,the problem of large deformation of soft rock has consistently plagued the majority of tunnel builders,and the large deformation of soft rock has greatly converged the newly excavated cavern chamber,causing the surrounding rock to invade the boundary of the building,which is easy to cause tunnel collapse,often leading to delays in the construction period,construction difficulties,and increased construction costs.Taking the Xincun Tunnel from Xinping(Canasan)to Yuanjiang(Hongguang)section of Yongjin Expressway in Yuxi City as the research background,this paper deeply studies the mechanism and control measures of large deformation of soft rock through literature research,theoretical analysis,numerical simulation and monitoring measurement.The specific research work of this paper is as follows:(1)On the basis of the elastoplastic theory,the creep deformation of soft rock is considered,and the Bingham model is introduced,and finally the displacement relationship considering viscoelastic plasticity is obtained.The deformation law of surrounding rock was explored,and on this basis,combined with the on-site engineering geology and hydrological conditions,the large-scale deformation mechanism of soft rock in Xincun Tunnel was proposed.The mechanism of action of different supporting structures is briefly introduced,and the principle of interaction between supporting structures and surrounding rock is analyzed in detail.(2)Long-term monitoring and measurement research was carried out on Xincun Tunnel,and the deformation law of surrounding rock in each construction stage was explored;Based on the on-site monitoring measurement data and the macroscopic phenomenon of large deformation of tunnel soft rock,the characteristics of large deformation of soft rock and the influencing factors of large deformation of Xincun tunnel were analyzed and summarized.(3)According to the geological situation of the large deformation section of Xincun Tunnel,the finite difference calculation software FLAC3D was used to establish a three-dimensional numerical model to explore the influence of different step height ratios and different cyclic excavation intakes on the deformation of surrounding rock.The results show that the optimal construction parameters are when the upper step is 4.0m,the middle step is 3.0m,the lower step is 3.0m,and the circular excavation advance is 1.5m.(4)The influence of different supporting parameters on the deformation of surrounding rock was explored by numerical simulation method on the optimization analysis of different bolt lengths,different bolt layouts,different steel arch spacings and models,and shotcrete thickness of the tunnel,and the research results showed that 5m long grouting anchors,50cm longitudinal steel arch spacing,I20b steel arch and 27cm shotcrete thickness were selected as the optimal supporting parameters.(5)Based on the above numerical simulation research,the optimized construction parameters and support parameters are applied to the actual project,the supporting effect is evaluated,and the effectiveness of the optimized support parameters in the large deformation section is verified.