考虑偏压作用的基坑抗隆起稳定性上限分析

为了研究偏压荷载对抗隆起稳定性的影响,提出了一种考虑偏压作用的基坑抗隆起稳定性计算方法,将墙后土体沉降变形近似简化为余弦曲线,从而在研究偏压作用对基坑抗隆起稳定性影响时可计入偏压荷载范围和坑边距等因素,同时在极限上限分析法的公式推导中考虑了土体各向异性对基坑抗隆起稳定性的影响。将该方法与HASHASH和WHITTLE提出的波士顿蓝黏土深基坑开挖有限元模型进行对比,通过数值算例研究了挡墙入土深度、基坑深度、土体各向异性、最下一道支撑到坑底距离及偏压荷载等因素对抗隆起安全系数的影响。研究表明:基坑抗隆起稳定性系数随着土体各向异性比的增加而增加,随着最下一道支撑到坑底距离增加而增大,发现偏压作用距离坑边在2倍基坑深度之内对抗隆起安全系数影响较大。最后结合案例分析验证了该方法的有效性。

Upper bound method for basal heave stability analysis of braced excavations considering surcharge loading effect

In order to study the influence of surcharge loading effects，a calculation method for the stability of the foundation pit considering the nearby surcharge is proposed． The settlement deformation of the soil behind the wall is simplified to a cosine curve，so that the distribution range and the lateral distance to the foundation pit of the surcharge load can be included． Meanwhilethe influence of soil anisotropy on basal heave stability is also considered in the limit upper bound analysis． The proposed method is verified through the comparisons with published results obtained by the finite element method for a deep pit excavation in Boston blue clay． Several numerical examples are given to study the influence of the retaining wall，the depth of the foundation pit，the anisotropy of the soil，and the distance from lowest strut to the excavation bottom on the safety factor of basal heave stability． This study shows that the stability coefficient of the foundation pit is increased with the increase of the soil anisotropy ratio and the distance from the bottom support to the bottom of the pit． The surcharge loading effect has a greater influence on the safety factor of the foundation pit when the lateral distance of the surcharge load to the foundation pit is within 2 times the pit depth． Finally，the effectiveness of the proposed method is verified by two case studies．