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以大量的室内抗剪强度试验为基础,分析了南京河西地区软土深基坑开挖时,坑底被动区土体在卸荷条件下的抗剪强度变化规律。通过研究分析表明:坑底被动区土体在卸荷状态下的抗剪强度指标和加荷状态下差别明显,有一定的残留强度;土体卸荷时抗剪强度受卸荷比的影响明显;随着卸荷滞留时间的延长,初期土体抗剪强度损失明显,后期逐渐不显著。最后通过基坑算例分析表明,加荷、卸荷条件下得到的土体强度指标的不同,将会对坑底被动土压力计算、基坑抗隆起稳定性和基底隆起量计算等方面产生显著影响,坑底不同深度土体受开挖卸荷影响的程度不同。所得结论对分析南京河西地区基坑工程的稳定性以及坑底被动区土体的加固设计等具有一定的参考价值。
Based on a large amount of indoor shear strength tests, the variation of shear strength of soils under passive load in the excavation of deep foundation pit of soft soil in Hexi area in Nanjing was analyzed. Through the research and analysis, the results show that the shear strength of soil in passive zone at the bottom of the pit is obviously different under the unloading condition, and there is a certain residual strength. The unloading shear strength of soil is affected by the unloading ratio ; With the extension of unloading residence time, the initial loss of shear strength of soil is obvious, the latter part of gradually less significant. Finally, the analysis of the foundation pit shows that the difference of the soil strength index under loading and unloading conditions will have a significant effect on the calculation of passive earth pressure at the bottom of the pit, the calculation of the anti-uplift stability of foundation pits and the calculation of the uplift of the foundation Affected, the bottom of the pit at different depths of soil affected by the excavation and unloading to varying degrees. The conclusions obtained are of certain reference value for analyzing the stability of foundation pit engineering and the reinforcement design of the soil in passive zone of Nanjing Hexi area.