空间效应对悬臂桩支护基坑连续破坏的影响研究
Influence of Space Effect on Progressive Collapse in Excavations Retained by Cantilever Piles

在局部破坏的情况下基坑可能发生大规模的连续破坏, 部分工程案例表明基坑的垮塌常发生在基坑侧壁的中部, 而不会延伸到坑角, 由此可见空间效应会对基坑的连续破坏及终止有较大影响．以悬臂桩支护的正方形基坑为例, 采用显式有限差分法研究了有空间效应作用下基坑发生局部破坏时的荷载传递机理, 并将其与无空间效应的基坑进行了对比．研究表明正方形基坑一侧中部发生局部破坏, 最大荷载传递系数会随失效桩数的增多先增大后减小, 因此连续破坏开展至一定范围即会终止．可见空间效应可能是导致连续破坏自然终止的一个原因．基坑尺寸越大, 荷载传递系数越大, 但当基坑增大至一定程度时, 远离坑角的荷载传递系数变化规律将接近于无空间效应时的情况．
A large-scale progressive collapse may occur in excavation under partial collapse. Some cases showed that collapses usually started from the central parts of excavation sides，and terminated before they evolved to the corners. It can be noted that space effect can significantly influence the development and termination of progressive collapse. The square excavation retained by cantilever piles was calculated by the explicit finite difference method，and the load transfer mechanism in excavations with space effect under partial collapse were investigated and compared with that in excavations without space effect. The results show that，when a partial collapse occurred in the central part of one side of a square excavation，the maximum load transfer coefficient increased first and then decreased with the increase in the number of failed piles，therefore，the progressive collapse terminated naturally when the collapse developed to a certain extent. Space effect may be one of the reasons why progressive collapse can terminate naturally. Load transfer coefficients will get larger with increasing excavation size. However，when the excavation is larger than a certain size，the load transfer coefficients of piles distant from the corner are similar to those in excavations without space effect