基坑抗隆起稳定的块体集上限分析

采用块体集上限法构造了基坑抗隆起稳定问题的运动许可速度场，分析了各种条件下不排水黏土基坑抗隆起稳定系数和破坏面特性。通过对考虑坑底坚硬土层、挡墙入土深度和基坑外侧地表超载条件下，块体集上限分析结果与已有文献结果的对比，验证了方法的有效性。块体集上限法克服了多块体上限法存在破坏面假设的缺点，不仅适用范围更广，同时可以得到更完整的基坑抗隆起优化破坏面。在考虑支护挡墙入土深度时，块体集上限法所得基坑抗隆起稳定分析结果优于多块体上限法和强度折减有限元法，具有较大优越性。

Upper bound analysis of basal stability in undrained clay based on block set mechanism

The block set mechanism is used to conduct upper bound analysis of the basal stability of braced excavations in undrained clay.Applications with consideration of different conditions are given to study the characteristics of stability factor and failure surface for excavations.The proposed mechanism is validated by case studies in which the factors of hard stratum,embedment depth of retaining wall and external load are taken into consideration.Improvement of the failure surface obtained from the Block Set Mechanism over that obtained from the multi-rigid-block mechanism(Qin et al.,2010) is achieved,since in the latter a partially assumed failure surface is adopted.Especially,for the cases of large embedment depth of retaining wall,the accuracy of solution obtained from the block set mechanism is better that that obtained from the multi-rigid-block mechanism(Qin et al.,2010) and the strength reduction finite element method(Faheem et al.,2003).