An analytical model for calculating vibrations from twin tunnels in a saturated poroelastic half-space

In this paper a semi-analytical solution is proposed for modelling vibrations from a twin tunnel in a saturated poroelastic half-space. The twin tunnels are simulated as two hollow cylinders made of a viscoelastic material. The half-space containing the two circular cavities is described as a two-phase poroelastic material. The wave field in the half-space with two cylindrical cavities is taken as the combination of down-going plane waves from the ground surface and outgoing cylindrical waves from each tunnel. With the help of transformation and translation properties of the plane and cylindrical waves the boundary condition at each scattering surface can be expressed with the appropriate coordinates. Numerical results suggest that the reflection effect of the ground surface has limited influence on the response of the tunnels, but has a greater influence on the free-field response near the surface. Compared with the single tunnel solution, the wave field above the twin tunnels is greatly distorted.