Semi-analytical solution for the dynamic response of a cylindrical structure embedded in a homogeneous half-space

This paper addresses the dynamic response of an infinitely long cylindrical structure embedded in an elastic half-space. The structure has a circular cross-section and its axis is parallel to the half-space surface. Excitation can be incident body waves or forces applied on the surface of the half-space and/or the structure. The model can be used to assess the integrity of structures when acted upon by seismic waves, to predict ground-borne vibration due to circulation of vehicles, and to infer about the safety of vehicles during earthquake events. Because the half-space and the structure surfaces possess different symmetries, the solution is not straightforward. In order to circumvent this difficulty, the physical domain is conformally mapped onto an auxiliary domain with a cylindrical symmetry, in which the free surface of the half-space and the surface of the structure are located at concentric cylindrical surfaces. The solution of the original boundary value problem is finally obtained by solving a set of algebraic equations. Truncation of the summation over circumferential modes is needed in the numerical implementation. Convergence tests, validations and comparisons of stresses and motions for twoand three-dimensional cases are presented and discussed as well as the advantages and disadvantages of the proposed method. Additionally, the effect of the presence of the tunnel is analysed by considering a limiting case of the half-space with just a cylindrical cavity of the same radius as the outer radius of the tunnel.