局部超挖对悬臂排桩基坑支护体系安全性能的影响

由局部超挖引发基坑大范围破坏的工程事故时有发生,但局部超挖对基坑整体安全性能的影响及其引发连续破坏的机理尚仍缺乏研究。以悬臂排桩支护的长条形基坑为例,采用模型试验和有限差分法对基坑局部超挖引起的荷载传递规律进行探索。结果表明:随着超挖深度的增大,由于土拱效应,超挖区外支护桩内力大幅增长,而超挖区内支护桩桩身弯矩先增加后降低或持续降低;大面积开挖深度相同时,随着局部超挖范围增大,邻近支护桩桩身弯矩与位移增幅逐渐增大并趋于稳定。研究成果初步揭示了局部超挖对支护桩内力的影响等荷载传递规律,可为防超挖引发基坑连续破坏研究和局部深坑设计提供参考。

Influence of Partial Over-excavation on Safety Performance of Excavation Retained by Cantilever Contiguous Retaining Piles

Although collapse cases caused by partial over-excavation are seen frequently, studies on the overall safety performance and the progressive collapse mechanism caused by partial over-excavation are still in lack. In this study, the load transfer mechanism of cantilever contiguous retaining piles of long strip excavation subjected to partial over-excavation were investigated by finite difference method and model test. Results revealed that with the increase of over-excavation depth, the internal force of the piles beyond over-excavation zone increased by a large margin due to soil arch effect, while the bending moment of piles within over-excavation zone increased first and then decreased or continued to decrease. When the excavation depth in a large area remained the same, the increments in bending moment and displacement of adjacent piles intensified gradually and tended to be stable along with the widening of partial over-excavation range. The research results reveal the load transfer rules reflecting the influence of partial over-excavation on internal force of piles.