黏土基坑抗隆起稳定分析的多块体上限解

为了将多块体上限法拓展应用到饱和黏土基坑抗隆起稳定性分析中,提出支护墙体刚性条件下,用于饱和黏土基坑抗隆起稳定分析的多块体相容破坏模式,并给出相应的上限计算能量方程。为检验多块体上限方法的应用情况,结合实际工程案例以及针对基坑宽度、坑底基岩埋置深度、支护墙体与土体间侧摩阻、支护墙体入土深度和土体强度非均质等对抗隆起稳定存在影响的因素进行计算和分析,并将多块体上限法计算结果与基于Terzaghi模式及Prandtl模式的上限解、Faheem强度折减有限元计算结果、Ukritchon的极限分析有限元计算结果做了广泛的对比。通过对比可以发现,所给出的多块体上限解是所讨论上限解中最优的,计算结果与Ukritchon的极限分析上限有限元计算结果较为接近,而多块体上限方法与Ukritchon的极限分析上限有限元相比,更容易实现,计算量也要小得多。通过大量计算以及与其他方法的对比可以发现,多块体上限方法在黏土基坑抗隆起中的应用是比较成功的。

MULTI-BLOCK UPPER BOUND METHOD FOR BASAL HEAVE STABILITY ANALYSIS OF BRACED EXCAVATIONS IN CLAY

Multi-block upper bound method is employed to analyze basal heave stability of braced excavations in undrained clay. For this purpose,the kinematically admissible multi-block failure mechanism is proposed firstly. Based on the proposed multi-block failure mechanism,the energy equation of the upper bound method is deduced again. To examine the application of the multi-block upper bound method in basal heave stability analysis,a lot of comparisons have been made with other existent solutions according to some true cases and the influential factors on the basal heave stability. These factors include the width of the foundation pit,the embedment of the hard stratum,the friction between the wall and soil,the insert depth of the wall and the strength nonhomogeneity. The existent solutions adopted include the upper bound solutions obtained by Terzaghi's mode and Prandtl's mode,and the Faheem's solutions obtained by the finite element method with strength reduction technique,and the Ukritchon's solutions obtained by the limit analysis finite element method. According to the comparisons,it can be found that the multi-block upper bound method gives the optimum solutions among the upper bound methods. It can also be found that the solutions given by the multi-block upper bound method are close to those obtained by the upper bound finite element method. It should be noted that the multi-block upper bound method is easy to program and needs less workload. Based on the calculations and comparisons,it may be found that the application of proposed multi-block upper bound method is successful.