深层搅拌桩施工引起的周围粘土的土性变化

本文通过室内试验验证了深层搅拌桩施工可以引起周围土体的物理,化学及力学性质的变化.其影响机理为高灵敏度粘土的触变性,土体劈裂,化学加固剂的侵入与渗透,胶结作用及固结压密.室内模型试验证明搅拌桩施工可以在周围土体引起约2倍桩径的土性变化领域.在此领域内含水量降低,pH值上升.此领域内先是强度下降,但7天内强度恢复,28天后强度增加3成.

PROPERTY CHANGES IN SURROUNDING CLAYS DUE TO INSTALLATION OF DM COLUMNS

This paper has identified five major factors causing property changes in surrounding soils during and after installation of deep mixing columns: soil thixotropy, soil fracturing, cement penetration and diffusion,cementation, and consolidation. Laboratory tests were performed to investigate the effects of soil thixotropy, soil fracturing, and cementation in a soft marine clay - Ariake clay. Laboratory tests were conducted to evaluate property changes in surrounding clays due to installation of deep mixing columns. Test results showed that an influential zone of property changes existed in surrounding clay ranging from the edge of the columns to the distance of about twice the radius of the columns. Within this influential zone, water content decreased with a distance close to the columns while pH values increased. Test results also showed that undrained shear strengths of the surrounding clays decreased during mixing but regained after a 7 - day curing period and continued increasing in 28 days in this study.