Abstract: Based on Biot’s theory and considering the property of moving loads, the boundary integral equations in the frequency domain-wave number for semi-infinite saturated soil is obtained by using the integral transform methods. The Cauchy type singularity of the 2.5D boundary integral equation is discussed and the effectiveness of passive vibration isolation using the open trench on the saturated soil is analyzed. Comparing the result with an existing one shows a good agreement. Numerical results show that, the present 2.5D boundary element method (BEM) is not only adaptable to solve the dynamic responses of moving loads with complicated boundary conditions, but also the computation time can be decreased greatly. For moving loads with high velocity, a considerable oscillation reduction of the pore pressure and the vertical displacement can be achieved by using open trench. The open trench barrier has no effect on the horizontal displacement for moving loads with lower velocity, even has the amplificatory effect on the vibration. Moreover, with the increasing of the distance between the vibration source and the open trench, the isolation effect of the surface wave propagation may be improved.

Key words: 2.5D boundary element method, open trench, moving loads, saturated soil, passive vibration isolation