| With the rapid development of my country’s transportation industry,more and more mountain highway tunnels are being built,and the phenomenon of bias in tunnels is not uncommon.If the phenomenon of bias is not taken seriously,it may cause engineering accidents.This article takes the HC05 bid section of the Chongqing Third Ring Expressway as the engineering background,and uses a combination of theoretical analysis and numerical simulation to study the mechanical properties and deformation laws of the biased tunnel under different conditions of surface inclination,tunnel depth,and construction methods.In order to analyze the stability of tunnel surrounding rock,the main research conclusions are as follows:(1)By modeling and analyzing the excavation of the bias section of the HC05 standard section tunnel,it is concluded that the right line excavation of the tunnel has a greater influence on the first principal stress value on the inner side of the middle rock wall and the left line,and the influence on deformation mainly depends After the tunnel is excavated,the size of the soil’s rebound deformation.Combined with the monitoring data,the tunnel vault settlement was fitted,and it was concluded that the hyperbolic curve fitting HC05 tunnel was the most suitable.The simulated vault settlement curve was compared with the actual engineering curve to determine the correctness of the model parameters.(2)The bias caused by topography causes obvious asymmetry in both horizontal and vertical stresses and displacements.The stress,deformation,and plastic zone of the deep-buried tunnel are larger than those of the shallow-buried tunnel.For the same tunnel,the bias effect on the shallow buried side is greater.(3)By not changing the buried depth of the tunnel and only changing the surface dip angle,the analysis shows that the bias phenomenon caused by the change of the surface dip angle is very obvious.As the surface dip angle increases,the stress,deformation,and axial force of the anchor rod are increasing.The severity of the bias pressure takes the inclination angle of the ground surface 25° as the turning point.When it exceeds 25°,the deformation and stress of the tunnel increase more obviously,which greatly exacerbates the asymmetry and the bias pressure is more serious.(4)By not changing the surface dip angle,only changing the tunnel burial depth,it can be seen that with the increase of the burial depth,the influence of the bias pressure is significantly weakened,and the tunnel stress,deformation,and anchor axial force are all in the symmetrical direction Development,this phenomenon is more significant at a depth of 30 m.(5)Based on the comprehensive analysis of the mechanical characteristics of different burial depths and slopes,when the tunnel surface inclination angle is greater than or equal to 25° and the burial depth is less than or equal to 25 m,the bias pressure has a significant effect on the internal stress distribution and displacement characteristics of the tunnel.In the excavation and support,the mechanical properties and deformation effects brought by the bias pressure are fully considered.(6)Establish a three-dimensional model to analyze the step method,CD method,reserved core soil method,and compare the displacement field,the deformation of the vault and the arch,and the shear stress field of the three.It can be seen that the CD method constructs the tunnel to the tunnel.The deformation control effect is better.It can be seen from the initial support stress that the CD method anchor rod is heavily distributed on both sides of the vault,and the vault is relatively safe.However,from the calculation time step,it can also be seen that the construction period of the CD method is too long,so this tunnel will be considered for some tunnels with poor V surrounding rock stability.The slightly better IV surrounding rock is recommended to excavate the tunnel by ring excavation and core soil method. |
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