This paper has identified four major factors causing property changes in surrounding soils during and after installation of deep mixing columns: soil fracturing, disturbance, thixotropy and consolidation, and diffusion of chemical agents. Laboratory and field tests were conducted to evaluate these changes during and after installation of deep mixing columns in soft Ariake clays. Both laboratory and field test data indicated that property changes existed within an influence zone ranging from the edge of the column to a distance of about twice the radius of the columns in surrounding clay. Within this influence zone, water content decreased with a closer distance to the columns while pH values and concentration of cations increased. Test results also showed that shear strengths of the surrounding clays decreased during the installation but regained after a short curing period (about 10 days in this study) and continued increasing in a long period. The increase of shear strengths in 30 days could reach 30% by average over the initial strength of the clays.
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