Abstract: In the upper limit analysis of anti-uplift instability of foundation pit in the past, the soil was usually divided into several rigid bodies, which neglected the shear deformation inside the rigid bodies and the size effect of foundation pit; thus, it was difficult to reflect the actual deformation mechanism of the foundation pit. The displacement increment of Rayleigh distribution function was selected, and the deformation model of narrow foundation pit under Terzaghi mechanism was established. The expression of the shear strength of soil considering soil anisotropy and over-consolidation ratio was adopted. According to the principle of upper bound method, the calculation method of safety coefficients of anti-uplift considering the geometric size of foundation pit was proposed. The influence rule of important parameters, including the geometric size of foundation pit, over-consolidation ratio and anisotropic coefficient of shear strength, on the safety coefficients of anti-uplift was quantitatively analyzed. The comparison between the classic foundation pit failure cases and the results of nonlinear finite element analysis shows that: in the proposed method, the influence of internal bracing erection on the stability of foundation pit is taken into account, and the influence of the width and anisotropy of foundation pit on the safety coefficient of anti-uplift can be considered.

Key words: tunnel engineering, anti-uplift of narrow foundation pit, upper limit method, continuous deformation, anisotropy, over-consolidation ratio

摘要： 以往对基坑抗隆起失稳的上限分析中，通常将土体分割成多个刚体快，忽略刚体快内部的剪切变形，且未考虑基坑的尺寸效应，因此难以反映基坑实际的变形机理。选择瑞利分布函数型式的位移增量，建立了Terzaghi机制下的窄基坑变形模型；采用了考虑土体各向异性和超固结比的土体抗剪强度表达形式，根据上限法原理，提出了考虑基坑几何尺寸的抗隆起安全系数计算方法；定量分析了基坑几何尺寸、超固结比和抗剪强度的各向异性系数等重要参数对抗隆起安全系数的影响规律。经典的基坑破坏案例和非线性有限元分析结果对比表明，考虑基坑几何尺寸的抗隆起安全系数计算方法考虑了内撑架设对基坑稳定性的影响，能够考虑基坑宽度和各向异性对抗隆起安全系数的影响。

关键词: 隧道工程, 窄基坑抗隆起, 上限法, 连续变形, 各向异性, 超固结比