Topographic Amplification of Seismic Ground Motion in Hills

Effect of slopes on topographic amplification has been rarely studied. This is an important issue for performance based design of foundations in hilly areas. The presented numerical study examines the seismic response of slope topography for different site conditions under vertically propagating SV waves. A single face slope, of constant base width, is considered. The influence of slope angle (β) and frequency of excitation on amplification of seismic ground motion is investigated. The two-dimensional Finite Element Analysis (2D-FEA) is adopted for the present seismic analysis of slope-topography. The behavior of soil is assumed as linear elastic. The side boundary is considered as a free field boundary to avoid reflection of ground motion. Complaint base condition is assigned at the bottom of the model. The incident ground motion is applied at the base of the FEA model and a far-field point from toe and crest is defined. The Seismic-Slope Topographic Amplification Factor (S-STAF) is expressed as a ratio of seismic response at the near field (along and surrounding the slope) and response at free field condition (horizontal ground surface). It was observed that the amplification increases as the slope angle and frequency of excitation increases. Further, the distance of point of the maximum peak ground acceleration from the crest increases as the slope angle increases.