A 2.5-D COUPLED FE-BE MODEL FOR THE DYNAMIC INTERACTION BETWEEN TUNNEL AND SATURATED SOIL

This paper presents a 2.5-D coupled FE-BE model to simulate the three-dimensional dynamic interaction between saturated soils and tunnels with arbitrary sections.The tunnel is modeled using 2.5-D FEM and the ground is modeled using 2.5-D BEM for saturated porous media.The auxiliary problems are introduced to eliminate the Cauchy singularity of the 2.5-D boundary integral equation.The coupled FE-BE equations are obtained using the continuity conditions on the soil-tunnel interface.The presented model is appropriate for tunnels with arbitrary sections and high computational efficiency.The model is verified through the comparison with the existing models.Finally, a case study of dynamic responses of a quasi-rectangular tunnel in saturated soil due to moving loads is presented.The effects of soil permeability on displacements and pore pressure are investigated.The results show that:(1) The pore pressure decreases drastically with the increment of soil permeability, while displacements are not susceptible to soil permeability;(2) the pore pressure and displacements are mainly distributed in the vicinity of 2m around the loading point;(3) In the direction of gravity, the dissipation of the pore pressure beneath the tunnel is faster than that of displacements;the distributions along the depth to tunnel invert of pore pressure and axial displacement are evidently influenced by the soil permeability.