基于优化宽度的基坑墙底抗隆起稳定性计算

Basal Stability Evaluation for Excavations by Using Optimization Width

现行规范的基坑墙底抗隆起稳定性验算采用Prandtl地基承载力计算式,假定地基基础发生双侧滑动破坏,不考虑围护体内侧土体对基坑隆起破坏的限制作用,与基坑工程实际状况不符。为考虑基坑内侧土体抗剪强度对基坑墙底抗隆起稳定性的贡献,在太沙基地基极限承载力计算式的基础上,利用优化方法求得基坑围护体单侧滑动隆起破坏的基础最小宽度,进而推导出基坑墙底抗隆起稳定性的地基承载力计算公式。计算结果表明,单向隆起破坏的稳定系数小于目前规范地基承载力计算模式的计算值,减小幅度在10%以内,偏于安全。

At present,the current code for checking the basal heave stability of excavation uses the Prandtl bearing capacity formula,which assumes that the foundation undergoes bilateral sliding failure and does not consider the limiting effect of the soil inside the enclosure on the heave failure of the excavation.This assumption is inconsistent with the actual conditions.Considering the contribution of the shear strength of soils inside the excavation to the basal stability at the bottom of excavation,the minimum width of the foundation for the one-way sliding uplift failure of the excavation enclosure wall is obtained based on the formula of the ultimate bearing capacity of the Terzaghi soils by utilizing optimization method.The formula of the ultimate bearing capacity for the basal stability at the bottom of the excavation is also derived.The results of this formula indicate that the factor of safety of the unilateral uplift sliding is smaller than the estimated value of the Prandtl bearing capacity formula in the current code.