考虑支撑作用的基坑抗隆起稳定安全系数计算方法

圆弧滑动法是国内规范计算基坑抗隆起稳定安全系数的主要方法之一。传统方法假设了滑动圆弧的圆心位置,最常用的位置是最下道支撑与围护墙的交点,这相当于假定支撑体系不会破坏,计算结果显然是偏于不安全的。给出一个计算模型,该模型不固定滑弧圆心位置,把通过试算得到的安全系数最小值作为最终的抗隆起稳定安全系数。同时,给出了考虑基坑宽度影响的算法。算例分析表明:针对传统地铁基坑,滑弧圆心可能位于最下道或以上各道支撑处,支撑体系的稳定性对安全系数有明显影响;当支撑极限轴力增大至临界值时可过渡为传统算法。进一步的分析表明,滑弧圆心最终位于基坑内一侧。所提方法是对传统圆弧滑动法的一个重要改进,适合在基坑设计和施工中推广应用。

Heave-resistant stability analysis method of foundation pit considering support

The circular sliding method is one of the most important methods for calculating safety factor of heave-resistant stability in China. Most commonly, the traditional methods assume the position of center of the slip arc are placed at the intersection of the bottom support and retaining wall, which means the support system will not be destroyed and the calculated result is obviously insecure. To solve this problem, the center of slip arc is not fixed in this paper. Through several calculations, the minimum safety value is adopted as the final safety factor of heave-resistant stability. Besides, a new method which considering the width of the foundation pit is also proposed in this paper. The analysis of the example shows that the center of slip arc may be located at the bottom support or above the bottom support for the insertion type of traditional subway foundation pit. It shows the stability of the support system has a significant impact on the safety factor. When the ultimate axial support force is large enough, the new method can be turned into the traditional circular slip method. Further analysis shows that the ultimate center of the slip arc is located inside of foundation pits. The proposed method is an important improvement to the traditional circular slip method, which is suitable for design and construction of foundation pit.