深层搅拌桩周围土体劈裂的研究与分析

现场测试结果表明：深层搅拌桩施工可以在周围土体中产生很高的超静孔隙水压力，其量值可能超过土体的静水劈裂压力。搅拌桩施工时和周围土体的相互作用可以用受剪的孔穴扩张过程来模拟。针对搅拌桩施工引起的周围土体的劈裂现象，提出了一种基于拉伸破坏原理的劈裂分析方法。分析结果表明：搅拌叶片的旋转对桩周围土体的劈裂起着很重要的作用。通过室内模型桩打设试验可以观测到搅拌桩周围土体的劈裂现象。分析现场搅拌桩施工时桩周土体中的孔隙水压力测试结果，表明现场施工可以引起劈裂。劈裂裂缝对于搅拌桩的性状有如下两方面的正面作用：其一，水泥浆体可以流入劈裂裂缝；其二，超静孔隙水压可以通过劈裂裂缝快速消散。这两者的作用加快了受扰动的周围土体的强度恢复。

Analysis research on soil fracturing around deep mixing column

Field investigation has shown that the excess pore water pressure induced by deep mixing column installation may be higher than the hydraulic fracturing pressure.The interaction behavior between the deep mixing column and the surrounding soil can be simulated as the shearing-expanding process of a cylindrical cavity.An approach is proposed to analyse the soil fracturing due to tensile force.Analytical results indicate that the rotation of the mixing blades has a significant effect on the clay fracturing in a close region around the column.The proposed method has been verified against laboratory test.Fracturing cracks have two functions: firstly,cement slurry can flow into the fracturing crack;secondly,excess pore pressure may dissipate through fractures.These two effects speed up the strength recovery of the surrounding soil.