考虑尺寸效应的狭窄型基坑稳定性分析

Stability Analysis of Narrow Foundation Pit Considering Size Effect

按传统基坑理论设计的狭窄基坑偏保守,造成较大的工程浪费。从基坑的尺寸效应入手,借助ABAQUS有限元软件,建立半无限空间弹性体和无限空间弹性体的支护结构模型,模拟桩撑围护结构在不同基坑开挖深度H、支护桩嵌入深度D、基坑宽度B组合情况下的力学特性;根据抗倾覆稳定理论和圆弧滑移理论,深入分析了H、D及B与基坑稳定性的内在关联;在实际工况下,基于两侧围护结构对坑底土体的约束作用确定基坑临界宽度,并据此将基坑分类,界定了现有规范在基坑设计中的适用性。研究结果可用于指导狭窄基坑的支护设计及施工,将产生较好的工程效益和社会效益。

The design of narrow foundation pits according to the traditional theories is too conservative and causes a large-scale engineering waste.Starting from the size effect,with the help of finite element software ABAQUS,the retaining structure models in semi-infinite elastic space and in an infinite one were established to simulate the mechanical performances of pile-supported envelopes under different combinations of the excavation depth H,the embedded depth of retaining pile D and excavation width B.Then,based on the anti-overturning stability theory and the circular slip theory,the intrinsic relationship between H,D and B as well as the stability of excavation was deeply analyzed.At last,in the actual working conditions,the critical width of foundation pit was determined based on the restraint effect of retaining structures on the soil below the bottom of the pit,and foundation pits are classified accordingly.Meanwhile,the applicability of existing codes was discussed.The research results can guide the design and construction of narrow excavation,which will bring more engineering and social benefits.