（奥雅纳工程咨询（上海）有限公司， 上海 200031）

［摘要］对于深大基坑工程，当桩基础在基坑开挖之前已经施工完成时，在基坑开挖过程中，桩基础将因土体卸荷松弛而导致承载力降低。另外，坑底以下土体隆起将在桩身产生附加拉力。从理论推导入手，提出一种既简便实用又能合理评估开挖卸荷对桩基基础影响的简化算法，主要用于计算开挖卸荷引起的桩基础承载力降低值和土体回弹引起的桩身附加拉力。并结合桩基础开展参数分析，获得了基坑开挖时桩基承载力和桩身附加拉力随开挖深度和桩径的变化规律，并提出几点应对建议，供工程技术人员参考。

［关键词］开挖卸荷； 土体回弹； 桩基承载力损失； 桩身附加拉力

中图分类号：TU473-1文献标识码：A文章编号：1002-848X(2019)22-0053-06

A simplified calculating method for calculating bearing capacity loss of pile foundation and additional tension force in piles caused by deep foundation pit excavation

Wang Mingmin, Sun Guangyu, Zhu Ligang, Zou Jinlin

(ARUP, Shanghai 200031, China)

Abstract:For deep and large foundation pit engineering, when pile foundation is completed before foundation pit excavation, the bearing capacity of pile foundation will reduce due to soil unloading procedure during foundation pit excavation. In addition, the soil swelling below the pit bottom will generate additional tension force in piles. Starting with theoretical derivation, a simplified calculating method was proposed which was simple, practical and could reasonably evaluate the impact of excavation unloading on pile foundation. This calculating method was mainly used to calculate the bearing capacity loss caused by excavation and the additional tension force in piles caused by soil swelling. Through parameter analysis of pile foundation, the variation law of   the bearing capacity of pile foundationa and additional tension force in pile with the excavation depth and the pile diameter  when the excavation of the foundation pit were obtained, and some suggestions for countermeasures were proposed for reference by engineers and technicians.

Keywords:unloading by excavation; soil swelling; bearing capacity loss of pile foundation; additional tension force in pile

作者简介：王明珉，博士，高级工程师，注册土木工程师（岩土），Email:cquwmm@163.com。