Research On Deformation,failure And Control Of Surrounding Rock In Tunnel Crossing Fault Fracture

With the implementation of the strategy of the western development and the strategy of rural revitalization,the construction of the traffic network in the West has gradually deepened.The mountain area in the western region accounts for a large proportion,and the proportion of tunnel engineering to the traffic network is large.Meanwhile,the geological conditions in the western region are complex and the faults are many,It is of great theoretical and practical significance to study the deformation law and control measures of surrounding rock when the tunnel passes through the fault zone.Based on a large number of literature research,this paper analyzes the influencing factors and failure characteristics of surrounding rock stability of the tunnel crossing fault zone,and summarizes the internal and external factors of surrounding rock stability;The deformation law of surrounding rock of tunnel under different types of fault zones and different arch spacing is studied by numerical simulation analysis.The deformation law of surrounding rock passing through fault zone under different excavation methods is obtained.Taking the project of crossing fault fracture zone of Changzhi queensling tunnel in Shanxi Province as an example,the deformation law of surrounding rock in the fault zone of the tunnel crossing fault zone is studied and the supporting effect is analyzed.The main conclusions are as follows(1)When the tunnel passes through the fault fracture zone,the maximum value of the settlement of the tunnel vault and the maximum value of the invert uplift are increasing with the gradual increase of the inclination of the fault zone;With the increasing width of fault fracture zone,the maximum value of tunnel crown settlement and the maximum value of invert uplift are increasing,and the range of key monitoring parts and settlement convergence of tunnel are increasing;With the increasing angle between the fault fracture zone and the tunnel axis,the maximum settlement of the tunnel vault and the maximum value of the invert uplift are increasing,and the range of key monitoring parts of the tunnel is decreasing;With the increasing of the arch spacing in the fault fracture zone,the maximum settlement of the tunnel vault and the maximum value of the invert uplift are increasing constantly,and the deformation of the key monitoring parts of the tunnel is not changed.(2)The order of the settlement of arch roof,the uplift of the invert and the convergence of the arch waist are: the whole section > the upper and lower steps > the three steps.Compared with the full section method,the settlement,uplift and convergence trend of the three step and step up method are slow,which will help to control the deformation of surrounding rock with other measures.(3)The results of field monitoring show that the cumulative deformation of surrounding rock near the fault zone tends to be stable after 32 days,and that of the conventional section tends to be stable after 27 days.When the pressure and axial force increase rapidly,the pressure and axial force distribution tend to be stable when the face is1.2m-6m away from the face of the face;The maximum settlement and convergence of faults occur on the side of fault deviation.The accumulated deformation of each monitoring section is far less than the reserved deformation,which indicates that the excavation and support scheme adopted in the design are reasonable and the support strength meets the requirements.(4)The comparison analysis shows that the measured values of maximum crown settlement,arch shoulder and arch waist convergence are not different from the simulation results,and the variation law is basically consistent.The influence range of both fault zones is about 50 m,but the range of measured mutation is larger than that of numerical simulation.The monitoring of tunnels in the influence range of fault zone should be strengthened to avoid problems due to insufficient support strength.