Dynamic response of a three-dimensional cavity in a layered half-space subjected to spherical P-waves

Blast-induced seismic waves have a crucial effect on adjacent underground cavities. In this paper, an indirect boundary integral equation method (IBIEM) is used to investigate the dynamic response of a three-dimensional (3D) cavity embedded in a layered half-space subjected to spherical P-waves. The free field of the spherical waves is solved by the modified stiffness method, and the scattered field is constructed by fictitious force sources near the cavity boundary. The accuracy of IBIEM is verified through comparison with other methods, and its numerical stability is also validated. With a numerical example of a spherical cavity in a single layered half-space, the displacement on the ground surface and the dynamic stress concentration factor (DSCF) on the cavity surface are discussed, and the influences of wave source position, incident frequency, soil layer thickness, and shear wave velocity ratio are examined. Results indicate that as the wave source moves toward the cavity, the displacement amplification above the cavity becomes increasingly pronounced, while the maximum DSCF changes non-monotonically. With increasing incident frequency, the DSCF generally decreases. For different soil layer thicknesses, the dynamic response characteristics of the cavity exhibit significant variations. The influence of the shear wave velocity ratio is strongly dependent on the incident frequency, wave source position, and soil layer thickness. Additionally, the dynamic response of a 3D cavity in a layered half-space differs significantly from that in a homogeneous half-space.