Effect of Partially Imperfect Interface on Dynamic Response of a Circular Lined Tunnel in an Elastic Half-Space Subjected to Plane SH Waves

Abstract

Loose zones and voids often exist behind the crown and the spandrel of a tunnel, and the interface between a tunnel lining and its surrounding medium is therefore partially debonded. To elucidate the partially imperfect interface effect on the dynamic response of tunnel, an analytical solution is derived for the scattering of plane shear horizontal (SH) waves by a circular lined tunnel with such an interface in a half space using wave function expansion and a piecewise integration method. A systemic parametric analysis based on the Xianglu Mountain Tunnel is conducted in a frequency domain. It is found that the effect of the spring model and the noncontact boundary model in simulating the partially imperfect interface is identical when the interface spring coefficient in spring model is small enough. The increment in the degree of interface imperfection (i.e., decreasing the interface spring coefficient or increasing the range of partially imperfect interface) tends to weaken the dynamic stress concentration factor (DSCF) but often intensifies displacements at the crown and spandrel of tunnel under SH waves at relatively high frequencies. The wave-trapping effect of the interface illustrated in the time domain is found to be the major mechanism for the partially imperfect interface modifying the stress and displacement fields in tunnel lining.