The current formula of critical hydraulic gradient is not adapted to solve critical hydraulic gradient of cohesive soil. Assume that the seepage failure mode of the cohesive soil foundation was cylindrical or inverted circular truncated cone, based on the calculation formula of the critical hydraulic gradient of Terzaghi, the analytical formula of the critical hydraulic gradient considering the influence of the shear strength of the soil was derived. Then, the seepage failure process of the clay layer was simulated numerically, and the effects of the clay layer thickness, failure radius, and shear strength indexes on the critical hydraulic slope were analyzed. The comparison results show that the numerical test results are in good agreement with the calculated results of the new formula. In addition, the critical hydraulic gradient of sandy loam and loess under different working conditions was studied severally by a self-made permeation failure instrument. The results show that the critical hydraulic gradient decreases with the increase of soil thickness and failure radius, and the maximum error between the test and the corresponding formula results is no more than 16%.

中文翻译：

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粘性土地基中流动土破坏的临界水力梯度理论研究

目前的临界水力梯度公式不适用于求解粘性土的临界水力梯度。根据Terzaghi临界水力梯度计算公式，假设粘性土地基的渗流破坏模式为圆柱或倒圆截锥，推导了考虑土体抗剪强度影响的临界水力梯度解析公式。然后，数值模拟了黏土层的渗流破坏过程，分析了黏土层厚度、破坏半径和抗剪强度指标对临界水力边坡的影响。对比结果表明，数值试验结果与新公式计算结果吻合较好。此外，利用自制的渗透破坏仪分别研究了不同工况下砂壤土和黄土的临界水力梯度。结果表明，临界水力梯度随着土体厚度和破坏半径的增加而减小，