Research On Dynamic Response Of Cross-fault Tunnel Based On Shear Beam Model

When the tunnel structure passes through the shattered fault zone and is affected by earthquake,it is extremely vulnerable.The deformation and failure mechanism of the crossactive fault tunnel structure under ground motion has always been a difficult problem in underground engineering research,and it has certain guiding significance for the application of anti-seismic and shock absorption measures for underground tunnel structures.In this paper,the cross-active fault tunnel structure is regarded as Shear beam placed on the elastic foundation beam along the longitudinal direction of the tunnel,and the seismic shear wave is simplified to the simple harmonic external excitation load on the cross section of the tunnel structure.The Green’s function method is used to derive the Green’s function of the dynamic response,and the ground motion response of the tunnel structure under the form of normal fault displacement is mainly studied.(1)The equilibrium differential governing equation of the Shear beam is derived from the force of the beam micro-element.Then,the steady-state dynamic response Green’s function of the Shear beam is obtained by separating the variables and Laplace transform.The obtained Shear beam dynamic response Green’s function is degenerated into the form of Euler beam.The validity of the analytical solution of the obtained Shear beam is verified by comparing with the existing literature data.Then the influence of different shear coefficient and external excitation frequency on the dynamic response of Shear beam is analyzed.(2)The resistant coefficient of elastic foundation is introduced into the steady-state dynamic response Green’s function of the Shear beam.Then the Volterra dislocation theory is introduced as the displacement response equation of the foundation,and the analytical analysis of the dynamic response of the tunnel structure across the fault tunnel is carried out.The effects of boundary conditions,tunnel length,focal depth,length of fault zone and the resistant coefficient of surrounding rock on the dynamic response of tunnel lining structure are studied.(3)The results of the dynamic response Green’s function are compared with the numerical simulation results.The numerical simulation is based on the F8 fault zone of the Longxi tunnel of the Wenchuan earthquake,and the tunnel lining structure is compared.By comparing the shear force and bending moment response curves of the tunnel lining structures in the longitudinal direction,the variation trend and extreme point distribution are observed,which proves the feasibility of the derived Green’s function of the dynamic response of the Shear beam.