Applying a time-domain boundary element method for study of seismic ground response in the vicinity of embedded cylindrical cavity

In this paper, an advanced formulation of a time-domain two-dimensional boundary element method (BEM) is presented and applied to calculate the response of a buried, unlined, and infinitely long cylindrical cavity with a circular cross-section subjected to SV and P waves. The applicability and efficiency of the algorithm are verified with frequency-domain BEM examples of the effect of cylindrical cavities on the site response analysis. The analysis results show that acceptable agreements exist between results of this research and presented examples. For a shallow cavity, the numerical results demonstrate that vertically incident SV wave reduces the horizontal components of the motion on the ground surface above the cavity, while it significantly increases the vertical component for a dimensionless frequency (η) of 0.5 and h/a=1.5. The maximum values of normalized displacements in vertical component of P waves are larger than horizontal component of SV waves for η=1.0. For a deeply embedded cavity, the effect of the cavity on the surface ground motion is negligible for incident SV wave, but it increases the vertical component of the displacement for incident P wave. Additionally, far and near distances from the center of the cavity show different amplitude patterns of response due to the cavity effect. Increasing the distance from the center of the cavity, the amplitude of displacement and the effect of the cavity attenuates significantly.