饱和黏土中钻孔灌注桩孔壁稳定性力学机制研究

发布时间：2018-03-06 16:25

本文选题：孔壁稳定性　切入点：钻孔灌注桩　出处：《岩土力学》2016年09期 　论文类型：期刊论文

【摘要】：将饱和软黏土中钻孔灌注桩孔壁稳定性问题视为半无限体内柱形孔的卸荷收缩问题。基于SMP准则改进的修正剑桥模型,采用应力空间变换方法推导了柱孔卸荷收缩问题的弹塑性解答,得出了孔壁临塑支护荷载和孔壁颈缩的解析表达式。在此基础上,提出了维持孔壁稳定所需最小泥浆重度和孔壁稳定安全系数的计算方法,并对影响钻孔稳定性的因素进行了研究。研究结果表明,饱和软黏土中钻孔灌注桩孔壁卸荷屈服后,孔壁周围土体处于弹塑性状态,钻孔颈缩量大,孔壁稳定安全系数较小;在泥浆支护条件下,饱和软黏土中钻孔灌注桩孔壁稳定性取决于土体重度、超固结比、土体内摩擦角及泥浆重度等因素,而与钻孔深度和孔径无关;土体超固结比和内摩擦角越大,维持钻孔稳定所需的临界支护压力和最小泥浆重度越小。在实际工程中,应在保证最小泥浆重度的条件下结合工程具体情况合理选取泥浆比例。
[Abstract]:The stability of borehole wall of bored pile in saturated soft clay is regarded as the unloading shrinkage of cylindrical hole in semi-infinite body. The modified Cambridge model is improved based on SMP criterion. The elastic-plastic solution of unloading shrinkage of column hole is derived by using the method of stress space transformation, and the analytical expressions of the load and necking of hole wall near plastic support are obtained. A method for calculating the minimum mud weight and the safety factor of the hole wall stability is proposed to maintain the stability of the borehole wall, and the factors affecting the stability of the borehole are studied. The results show that the borehole wall of the bored cast-in-place pile in saturated soft clay yields after unloading and yielding. The soil around the hole wall is in an elastic-plastic state, the borehole neck shrinkage is large, and the safety factor of the hole wall stability is small. Under the condition of mud support, the stability of the hole wall of the bored pile in saturated soft clay depends on the soil mass, the overconsolidation ratio, the stability of the borehole wall in the saturated soft clay, The larger the overconsolidation ratio and the internal friction angle, the smaller the critical support pressure and the minimum mud gravity required to maintain the borehole stability. The proportion of mud should be reasonably selected under the condition of ensuring the minimum mud weight in combination with the specific conditions of the project.
【作者单位】：同济大学岩土及地下地下工程教育部重点实验室;同济大学地下建筑与工程系;
【基金】：国家自然科学基金项目(No.41272288)~~
【分类号】：TU473.1

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