The seismic performance of a piled raft foundation with grid-form deep mixing walls (DMWs) in soft ground under strong earthquake loads is numerically evaluated in this study. A base-isolated 12-story building located in Tokyo is modeled as a detailed three-dimensional finite element soil structure interaction model. In the previous study, the model was calibrated using the records of the 2011 off the Pacific coast of Tohoku Earthquake. Based on this result, seismic response analyses under strong earthquake loads are conducted in this study. Artificial earthquakes that are officially notified for performance design in Japanese building design codes are used as strong earthquakes. For the constitutive model of stabilized soil, the elasto-plastic model that is able to evaluate shear and tension failure is used, and it is also able to evaluate the post-peak tension-softening assuming the energy release during the formation and opening of cracks in the DMWs. Based on the analysis results, it is found that even though the induced stress in the DMWs reaches the tensile strength and softens, the grid-form DMWs are quite effective at reducing the bending moment of the piles to an acceptable level under the strong earthquake load.
Subjects: piled raft foundation, deep mixing walls, soil and structure interaction analysis
Author: Yoshimasa Shigeno, Kiyoshi Yamashita and Junji Hamada
Publisher: DFI, EFFC