Abstract: Based on the wave function expansion method and the cylindrical wave–plane wave conversion technique, this study investigates the scattering of plane SH waves by a circular cavity in an overburden layer overlying an elastic half-space. A series solution for the dynamic response is derived. The solution accuracy is ensured by strictly satisfying the stress-free condition on the cavity surface and the continuity conditions of displacement and stress at the layer interfaces. Its validity is further verified by comparing the results of a degenerate model with a classical solution. A systematic parameter analysis is conducted to examine the influence of the modulus ratio between the overburden layer and the half-space, overburden layer thickness, cavity burial depth, dimensionless frequency, and incident angle. The results indicate that as the modulus ratio increases, the displacement amplitude decreases, whereas the shear stress amplitude increases. The overburden thickness causes fluctuations in response amplitude due to the periodicity of the transmission coefficient, although the distribution pattern changes little. Shallower burial depths result in more significant surface responses of the cavity. An increase in dimensionless frequency intensifies circumferential fluctuations and raises the overall amplitude, but the displacement at the cavity crown diminishes due to weakened diffraction. The incident angle substantially alters the symmetry and amplitude of the response, with oblique incidence yielding higher amplitudes.

Key words: circular cavity, overburden layer, wave scattering, series solution