3-D scattering of obliquely incident Rayleigh waves by a saturated alluvial valley in a layered half-space

In this paper, three-dimensional (3-D) scattering of obliquely incident Rayleigh waves by a saturated alluvial valley embedded in a layered half-space is studied in the frequency domain by using the indirect boundary element method. The total responses are assumed as the sum of the free-field responses and scattered-field responses. The free-field responses are calculated using the direct stiffness method and the scatter-field responses outside and inside of the valley are simulated by applying two sets of fictitious moving distributed loads and pore pressures on the interface of the valley. The amplitudes of the fictitious distributed loads and pore pressures are determined from the boundary conditions. The method is validated by comparing the results with the results published in the literature, and numerical results are obtained for a saturated valley embedded in a uniform saturated half-space and in a single elastic layer overlying elastic half-space. The effects of incident frequency, incident angle, porosity, drainage condition, and soil layers on the dynamic responses are discussed. It is found that 3-D scattering is different from the 2-D case. As the porosity decreased, the pore pressures around the valley became smaller but their oscillations became violent. The wave fields in a layered site are determined by the “dynamic interaction between valley and the layered half-space” and the dispersion characteristics of Rayleigh waves for the given layered-half-space.