饱和软黏土中开孔防沉板基础上拔特性研究
Uplift behaviors of perforated mudmats in soft saturated clay
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摘要: 在软黏土地基中,开孔能有效降低防沉板基础上拔阻力,减小防沉板基础回收难度。对6种具有不同开孔形式的防沉板模型进行了饱和软黏土中的上拔试验,测定了上拔过程中防沉板与土体接触面间的吸附力,揭示了上拔阻力的构成与发展规律,阐明了开孔率和有效宽度对上拔阻力和接触面间吸附力的影响规律。采用有限元方法模拟了防沉板基础的上拔过程,建立了上拔力作用下饱和软黏土地基的破坏模式,构建了采用极限分析法计算防沉板上拔阻力的机动场,推导了上拔阻力的上限解,得到了可以同时考虑防沉板开孔率和有效宽度的上拔阻力系数Nc的计算公式。对比验证结果表明:与Skempton公式不同,求解的上拔阻力随开孔率的增加呈非线性降低规律。Abstract: Perforation can cause lower uplift resistance in soft clay, giving rise to less difficulty of the retrieval of “mudmat” shallow foundations. Six different perforated forms are designed to perform in the model tests on the uplift behaviors in soft saturated clay. The suction that develops at the mudmat-soil interface is conducted during the whole uplift procedure. The composition and development laws of uplift resistance are revealed. The characteristics of how the perforation ratio and effective width reduce uplift resistance and suction at the mudmat-soil interface are obtained. Numerical simulation is used to figure out the uplift behaviors of perforated mudmats in soft saturated clay on the basis of model tests, revealing different soil failure modes in soft saturated clay. The limit analysis method is used to calculate the uplift resistance though the velocity fields from numerical simulation results. The upper bound solution of uplift resistance is derived, and uplift bearing factor Nc is obtained considering the influences of perforation ratio and effective width. The study shows that compared with that of the Skempton formula, the uplift resistance solved in this study has a nonlinear reduction law with the increase of perforation ratio.