Research On The Forced Influence Of Cross-active Fault Tunnel Under Strike-slip Dislocation

Many active faults dominated by strike-slip faults exist in western region of China,which makes it inevitable to cross the weak intercalations in the geology during the construction of tunnel.And the tunnel structure and the earth’s surface under different geological conditions will be ruptured to varying degrees and be in the threat of dislocations.In view of those conditions,this thesis takes the Xianglu mountain tunnel of the center of Yunnan water diversion tunnel as the research background,and uses model experimental tests and numerical analysis methods to carry out a study on the forced influence of surrounding rock and liner of crossing fault tunnel under strike-slip fault.Main contents include as following:(1)A set model experimental tests are carried out to obtain failure modes and catastrophic mechanism of surrounding rock and liner under strike-slip fault,in which two experimental conditions are considered relying on whether a fault width is contained or not.Additionally,the distribution law of the two-dimensional displacement field of the overlying of surrounding rock was obtained with the guidance of incremental-guided Particle Image Velocimetry technology,PIV for short.The results showed that the deformation mode of the tunnel under strike-slip fault was distributed in a shape of‘S’,and the tunnel failure mode was a combined failure pattern of being bended,tensioned and even sheared.Moreover,the surface fracture range of the overlying surrounding rock is related to the fault width and the existence of that has an inhibitory effect on the expansion of surface cracks along the surrounding rocks.(2)The accuracy of the experimental model test was verified by means of numerical simulation.Based on the numerical modeling,a sensitivity analysis including four main parameters of the fault was carried out.The results showed that the conclusions under those two methods of model test and numerical simulation are in good agreement,and the strain distribution law along the longitudinal direction of the tunnel on the left and right sides of the tunnel is relatively close.Futhermore,the top and botton of the tunnel in the central section of the fault zone will be subjected to more severe shear deformation.In addition,through the analysis of the macroscopic deformation,internal force and stress of the tunnel,the parameter sensitivity of the four main parameters was obtained.The parameter sensitivity of the four including fault dislocation value,fault zone width,fault width,surrounding rock strength and fault dip angle gradually decreased.(3)Based on the Xianglu mountain water diversion tunnel of the central Yunnan,a largescaled finite element numerical modeling was established,and the liner deformation and failure mechanism of the Xianglu mountain tunnel under strike-slip fault was carried out,and the liner of the tunnel was revealed by the research.Corresponding fortification positions were proposed according to the law of failure.The results showed that the left and right sides of the arch in the fault fracture zone are in a state of being tensioned and compressioned,while the top and bottom of the tunnel are in a state of shear stress.The research results can provide a theoretical fortification reference for the key vulnerable parts of tunnels.