Abstract: Based on the wave propagation theory of saturated porous medium proposed by Biot and wave propagation theory of inviscid compressible ideal fluid, considering the fluid-mechanical coupling of underwater saturated soil, an analytical solution of the scattering problem of the incident plane P1-wave around the undersea cavity is presented using the Hankel function integral transformation method (HFITM). Compared with the “large arc hypothesis” in traditional research, the HFITM can better deal with the surface boundary of the half space. Using the analytical solution, the effects of permeability conditions of the cavity, incident angle, incident frequency, seawater depth and the porosity of saturated soil on the displacement (horizontal and vertical displacement) of the interface between water and saturated soil and the stress (hydrodynamic pressure and total circumferential stress) on the surface of the cavity. The results show that the permeability conditions on the surface of the cavity have a small effect on the displacement of the interface between water and saturated soil; as the oblique incident angle increases, the vertical displacement on the interface between the ideal water and saturated soil decreases; the horizontal displacement of the interface between water and saturated soil increases as the incident frequency increases; when the depth of seawater is 2.5 times the wavelength of the SV-wave, the maximum horizontal displacement on the interface between water and saturated soil and hydrodynamic pressure on the surface of the cavity are the largest; the displacement of the interface between water and saturated soil and the total circumferential stress on the surface of the cavity decrease with the increasing porosity, while the hydrodynamic pressure on the surface of the cavity increases.

Key words: undersea cavity, plane P1- waves, scattering problem, seismic response, analytical solution