Seismic response analysis of ground improved by Deep Mixing considering spatial variability

Abstract

When designing a solidification treatment method for a caisson-type quay in Japan, it is necessary to conduct an seismic response analysis under the level 2 earthquake ground motion. On the other hand, the ground improved by deep mixing method exhibits significant spatial variance of its mechanical properties due to heterogeneity of naturally deposited ground and non-uniformity of cement-mixing. In the Japanese design standard for solidification treatment method, instead of considering this spatial variability, it is general to conduct the analysis on uniform ground with reduced average unconfined compression strength of in-situ improved ground. In this paper, we conducted series of analyses on the ground with variability, directly considering the spatial variability of the shear strength, in order to achieve a more low-cost design. Furthermore, we identify the improvement area that significantly affects the residual horizontal displacement of the caisson, and propose a low-cost and safe design method implementing partially high-quality improvement.