开挖卸荷条件下抗拔桩破坏机理及承载力分析

Failure Mechanism and Bearing Capacity of the Anti-pulling Pile Unloaded at Excavation

摘要:

随着大型基础施工进度和地层限制等要求的提高，抗拔桩基础先于基坑开挖施工逐渐成为发展趋势。伴随着基坑开挖产生的大面积卸荷，抗拔桩受力状态和极限承载力将产生重大变化。本文将颗粒流数值模拟与极限平衡理论分析相结合，剖析开挖卸荷条件下，抗拔桩破坏机理和极限承载力特征。分析表明：抗拔桩周边土体的破坏特征为倒锥台形，存在线性破坏面和破坏角；开挖卸荷对桩周土的破坏角影响不大，但桩长对破坏角的影响显著；根据机理研究结果，建立理论分析模型，推导出较实用的抗拔桩承载力及其损失比理论公式，并针对前人的模拟试验结果对理论公式进行了检验。

Abstract:

With more demanding requirements of the large scale foundation on the construction progress and ground limitation, construction of the anti-pulling pile before the foundation pit excavation has gradually become the trend. The stress state and ultimate bearing capacity of the pile will change greatly with massive unloading at foundation pit excavation. By combining the numerical simulation of the particle flow with the theoretical analysis of the limit equilibrium, the failure mechanism and ultimate bearing capacity of the anti-pulling pile unloaded at excavation is analyzed. The analysis shows that the damage characteristics of the surrounding soil is an inverted cone shape with the linear failure surface and failure angle. Unloading at excavation has little influence on the failure angle of the surrounding soil, but the influence of the pile length on the failure angle is significant. According to the research results of the mechanism, the theoretical analysis model has been established with the theoretical formula for the bearing capacity and loss ratio of the pile derived. The theoretical formula has been verified by the existing simulation test results.