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天然黏土表现出明显的强度各向异性,在软黏土地区中的基坑抗隆起分析时有必要考虑土体各向异性的影响。针对桩墙式支护基坑绕下道支撑的圆弧滑动抗隆起稳定模式,采用基于空心圆柱仪(HCA)杭州原状软黏土试验结果的土体强度各向异性不排水强度公式,根据极限平衡法推导得到坑底抗隆起稳定分析公式。结合算例,讨论了土体强度各向异性、挡墙入土深度、最下道支撑和坑底间的距离等因素对坑底抗隆起稳定的影响,比较了该文方法与传统方法结果的差别,指出不考虑土体强度各向异性的软黏土基坑抗隆起分析和基于传统Casagrande各向异性公式的抗隆起分析都将高估杭州软黏土基坑的抗隆起稳定性。最后采用该方法分析杭州某失稳基坑实例,通过与已有方法结果的对比,验证了该文方法的合理性。
Natural clay shows obvious anisotropy of strength. It is necessary to consider the influence of soil anisotropy in the analysis of foundation pit anti-uplift in soft clay area. Aiming at the stability mode of circular sliding anti-uplift supported by the bottom support of pile-wall supporting foundation pit, the formula of undrained strength of soil anisotropy based on the test results of HCA Hangzhou original soft clay was adopted. According to the limit equilibrium The law of stability analysis of pit bottom anti-swelling is deduced. The effects of anisotropy of soil mass, depth of embankment, the distance between the bottom support and the pit floor on the anti-swelling of the pit bottom are discussed. The differences between the proposed method and the traditional method are compared It is pointed out that the anti-uplift analysis of soft clay foundation pit without considering the strength anisotropy of soil and the anti-uplift analysis based on the traditional Casagrande anisotropy formula all will overestimate the anti-swelling stability of the foundation pit of Hangzhou soft clay. Finally, this method is used to analyze a certain instability foundation pit in Hangzhou. By comparing with the results of the existing methods, the rationality of this method is verified.