竖向土工加筋体对碎石桩承载变形影响的模型试验研究

在碎石桩桩顶一定深度内包裹竖向土工加筋体形成筋箍碎石桩,能有效提高碎石桩的承载能力,控制复合地基沉降量。采用分级加载方式,设计并完成了两组较大比例室内模型试验,对比分析了筋箍碎石桩和传统碎石桩的承载变形特性,进而探讨了筋箍碎石桩的加筋机理和鼓胀变形模式,重点分析了竖向土工加筋体的应力应变特征。分析结果表明：竖向土工加筋体能有效约束碎石桩的侧向鼓胀,在微小侧向变形内提供足够的径向约束应力;筋箍碎石桩的最大鼓胀变形多发生于加筋体以下区域,其破坏模式与筋体材料、桩体、桩周土体及其相互作用和协调变形密切相关;筋箍碎石桩的桩顶和桩底桩土应力比均明显大于传统碎石桩,上部土工加筋体在提高桩体刚度的同时,可有效地将上部荷载传递至桩底较好土层。

Model tests on influence of vertical geosynthetic-encasement on performance of stone columns

Wrapping the individual stone columns with vertical geosynthetics can effectively improve the load performance of stone columns and control the settlement of composite foundation. The quantitative improvement of loading capacity of geosynthetic-encased stone columns is investigated through two series of laboratory model tests conducted on stone columns installed in soft soils in a large scale testing tank. Bugling failure models and reinforcement mechanism are discussed, and the stress-strain characteristics of vertical encasement are analyzed. The results from the loading tests indicate significant improvement in loading capacity of the stone columns due to vertical encasement. The biggest bugling deformation occurs just below the encasement, and the bugling model involves the interaction between the stone column, vertical geosynthetic-encasement and surrounding soils. The column-soil stress ratio of composite foundation for the encased stone columns is much higher than that for the ordinary stone columns. The vertical geosynthetics greatly improve the stiffness of stone columns and help to transfer the upper load to the bottom layer of soils.