Seismic Response Validation of DM Treated Liquefiable Soils

When structures are founded on loose saturated sandy soils, deep mixing (DM) is often an attractive remedial measure against liquefaction. The locations away from deep mixed treated area represent free-field, while strong nonlinear soil-structure interaction effects are expected around the treated area. A simplified approach that is flexible enough to accommodate important factors that affect DM treated soil sites has been recently developed. The seismic response characteristics of the DM sites have been assessed based on the residual porewater pressure response (or liquefaction) since this is a widely-used engineering response indicator. The seismic response of a DM treated field case, that is representative of the foundation under the fourteen-story Oriental Hotel building in Japan, was computed using the proposed approach. This hotel was subjected to intensive shaking during the 1995 Hyogoken-Nanbu (Kobe) Earthquake (M = 6.9) but suffered negligible damage. The proposed approach showed the effectiveness of the treated columns in reducing the porewater pressure response at locations closer to the DM treated zone. The effectiveness of treatment is significant, especially near the surface. Absence of liquefaction within the cells and at locations closer to the edge column would have played a positive role relative to the accepted performance