Soil fracturing of the surrounding clay during deep mixing column installation

Abstract

During deep mixing (DM) column installation, excess pore pressure arises in the surrounding clay due to the injection of chemical admixtures and the shearing action caused by blade rotation. The excess pore pressure is greater than the in-situ effective stress, resulting in fractures in the surrounding clay. Pore water infiltrates into fractures, and the consolidation of clay is accelerated. The chemical admixture penetrates into the fractures and thereby exchangeable cations diffuse into the surrounding clay effectively. All of these effects accelerate the strength increase of the surrounding clay after the installation of DM columns. The main objective of this study is to confirm the aforementioned phenomena. These phenomena are verified through (1) a laboratory vane shear test, (2) a laboratory test on a model column made in a model clay ground, and (3) full-scale field tests on DM column installation.