Seismic Response Analysis Of Tunnel Structures In Saturated Soils With Fluid-solid Dynamic Coupling Is Presented

In recent years,the trend of vigorously developing new ways of underground transportation at home and abroad is increasing day by day.,however,the domestic many areas in the high earthquake intensity and earthquake damage probability larger seismic belt,and frequent high intensity earthquake disasters in recent years show that the seismic design and construction of underground structures is to be civil workers need to solve the problem,therefore,for in the rivers and lakes of saturated soil under the seismic response of the tunnel structure research is particularly important.Based on the dynamic theory of Biot porous media and with the help of the finite element software Comsol Multiphysics which has an absolute advantage in solving the problem of multi-field coupling,this paper studies and simulates the seismic response of the tunnel structure in saturated soil under different conditions.Specific research work includes:1.Taking advantage of the advantages of Comsol Multiphysics in solving multi-field coupling problems,through the secondary development of the PDE module provided by Comsol,the solution of the wave equation in the form of u-w coupling of Biot saturated porous media is realized.2.Establish the application method of viscoelastic artificial boundary conditions of saturated porous media and the corresponding input method of wave motion based on Comsol software,and realize the seismic response analysis of saturated soil site by Comsol finite element software.Compared with the analytical solutions of typical endogenous and exogenous problems,the feasibility and correctness of the method are verified.3.The Comsol finite element analysis model of saturated soil and tunnel structure was established to simulate and analyze the seismic dynamic response of the structure in terms of displacement,stress and pore water pressure under the action of P wave and SV wave respectively at different tunnel depths and under the condition of different soil properties.The main conclusions are as follows:(1)Under the action of two different seismic waves(P wave and SV wave),the overall displacement time variation trend of the structure is similar to that of the input seismic wave.Moreover,when the relative buried depth of the tunnel and the elastic modulus of the soil increase,the overall displacement inside the tunnel tends to weaken.(2)With the increase of the buried depth of the tunnel,the stress of each key node and the pore water pressure outside the structure will fluctuate in a reciprocating manner,first increasing and then decreasing,when the structure is subjected to two different seismic forces.Therefore,it is not comprehensive to improve the overall seismic performance of the structure only by changing the buried depth,and the optimal buried depth of the structure should be determined by comprehensive consideration of geological conditions,construction technology,economic level and other practical engineering conditions.(3)Under the action of earthquake,the relative stiffness(flexibility ratio)of the structure and soil mass has a significant impact on the seismic performance of the tunnel.When the flexibility ratio increases,the stress everywhere in the structure and the water pressure of the outer pore will decrease accordingly,and the maximum stress reduction reaches 47.7%.The greater the flexibility of the tunnel structure to the surrounding soil,that is,the greater the flexibility ratio,the better the seismic resistance of the structure.But only increase the strength of the structure,will make its flexibility ratio reduced,is not conducive to improve the seismic performance of the structure.