Seismic Response Analysis Of Crossing-Fault Tunnel

The Sichuan-Tibet line is one of the important construction projects in our country.It faces extremely harsh engineering geological conditions,frequent strong earthquakes and densely distributed fault zones.The terrain is ups and downs.The whole project need to build many crossing-fault tunnels which located in the strong earthquake zone.Historical records show that crossing-fault tunnels are more susceptible to earthquake damage than tunnels in other fault-free areas.It posed a large threat to people’s lives and property.Therefore,it is of great significance for construction of the Sichuan-Tibet line to research the seismic response of crossing-fault tunnels under earthquake action.The failure of a crossing-fault tunnel under the action of an earthquake can essentially be classified as a near-field nonlinear wave problem.When conducting dynamic analysis,it is necessary to consider not only the influence of ground motion,but also the influence of various factors such as material nonlinearity and site conditions.Based on the near-field wave theory,this paper uses the modified Hoek-Brown strength criterion and the ground motion input method based on viscoelastic artificial boundary to analyze and study the seismic response of crossing-fault tunnel by using numerical simulation method,so as to obtain the seismic response law of crossing-fault tunnel.The main research includes1.Establishment of material constitutive model.In this article,a modified Hoek-Brown strength criterion in the form of a two-parameter partial function is used to characterize the nonlinear characteristics of the rock,and the plane tangent equivalent method is used to transform it into instantaneous equivalent Mohr-Coulomb parameters to ensure the numerical solution process.2.Based on the ABAQUS finite element software,combined with the viscoelastic artificial boundary,the input method of vertical incidence and oblique incidence of ground motion in a two-dimensional plane wave homogeneous half-space site is established.The automatic application of the viscoelastic artificial boundary and the automatic addition of the equivalent nodal force are realized by writing MATLAB programs,and the input of ground motion is realized.3.Research on dynamic response of crossing-fault tunnels under earthquake action.The author discuss from various influencing factors such as fault properties,fault dip angle,fault width,fault depth,surrounding rock properties,tunnel section radius,and seismic wave incidence angle,etc.Then sum up therelevant laws from them so as to guide actual engineering needs.