动态承压水作用下深基坑底部弱透水层的出逸比降解析研究

发布时间：2018-05-10 05:14

本文选题：承压水头变化 + 基坑　；参考：《岩土工程学报》2017年02期

【摘要】：根据深大基坑坑底弱透水层的一维越流模型,求解了承压水头变化引起的坑底弱透水层中的超静孔隙水压力和出逸比降的解析表达式。当坑底土层渗透系数较大时,出逸比降计算结果与传统方法的出逸比降求解结果一致,验证了出逸比降解析解的正确性。基于出逸比降解析解,分析了动态承压水作用下坑底出逸比降的变化规律和影响因素。结果表明:当基坑坑底弱透水层厚度一定时,土体渗透系数、压缩模量或承压水头波动周期越大,出逸比降波动越明显,幅值越大,相位差越小;出逸比降影响因素可通过与土体渗透系数和压缩模量正相关,与承压水头波动的角频率和弱透水层厚度的平方负相关的无量纲因子统一表示。最后通过工程实例表明,对于坑底弱透水层渗透系数较小的情况,降承压水头引起的出逸比降减小幅度不大并存在明显滞后性,对基坑的抗渗流稳定性具有不利影响。
[Abstract]:Based on the one-dimensional overflowing model of weak permeable layer at the bottom of deep and large foundation pit, the analytical expressions of excess pore water pressure and escape ratio drop caused by the change of confined water head in weak permeable layer of deep foundation pit are obtained. When the permeability coefficient of the bottom layer is large, the calculated results of the escape ratio drop are consistent with those of the traditional method, which verifies the correctness of the analytical solution of the escape ratio drop. Based on the analytical solution of escape ratio drop, the variation law and influencing factors of escape ratio drop under dynamic pressure water are analyzed. The results show that when the thickness of weak permeable layer at the bottom of the pit is constant, the larger the fluctuation period of soil permeability coefficient, compression modulus or confined water head is, the more obvious the fluctuation of escape ratio is, the larger the amplitude is, and the smaller the phase difference is. The influencing factors of escape ratio drop can be expressed by the dimensionless factor, which is positively correlated with the soil permeability coefficient and compression modulus, and negatively correlated with the angular frequency of the pressure head fluctuation and the square of the thickness of the weak permeable layer. Finally, the engineering example shows that for the case where the permeability coefficient of the weak permeable layer at the bottom of the pit is small, the drop of escape ratio caused by the water head under the pressure drop is not large and there is obvious hysteresis, which has a negative effect on the stability of seepage resistance of foundation pit.
【作者单位】：浙江大学滨海和城市岩土工程研究中心;浙江大学软弱土与环境土工教育部重点实验室;
【基金】：国家自然科学基金项目(51278462,51278453,51678523);国家自然科学基金重点项目(51338009) 教育部高校博士点专项科研基金项目(20120101110029)
【分类号】：TU753

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