考虑安全系数的坑中坑开挖基坑失稳模式分析  

Analysis of Instability Mode of Pit-in-Pit Excavation Considering Safety Factor

作　　者：郭涛 GUO Tao(JSTI Group,Nanjing Jiangsu 210019 China)

机构地区：[1]苏交科集团股份有限公司,江苏南京210019

出　　处：《江苏建筑》2023年第1期83-86,90,共5页Jiangsu Construction

摘　　要：坑中坑基坑是工程中较为普遍的一种基坑形式,基坑开挖后再次开挖引起的应力释放,对基坑变形及整体稳定性造成不同影响。文章以南京某快速路坑中坑基坑为工程背景,结合Plaxis有限元计算,采用Hardening-Soil土体本构模型,考虑基坑抗隆起安全系数,分析外墙插入比λ与坑趾系数α对基坑稳定系数的影响,揭示坑中坑基坑两种失稳破坏模式,结果表明,当λ>0.25或α<1.5时,内外基坑失稳时形成贯通的圆弧滑动面,且安全稳定系数随λ增大和α的减小而增大,但当α<1.0时,外坑台宽的减小会使滑动圆弧面缩小,承受抗滑土体的被动土范围减少,安全系数减小;λ<0.25或α>1.5时,基坑隆起破坏点出现在内外坑不同位置,内外基坑可视为两个独立基坑进行稳定验算。研究成果可为坑中坑基坑稳定性验算与支护提供参考。The foundation pit in the foundation pit is a common form of foundation pit in the project.Excavation of the foundation pit will cause the release of stress after excavation, and have different effects on the overall stability and deformation of the foundation pit. Taking the foundation pit of Nanjing Expressway as the engineering background, combined with the finite element calculation of Plaxis, the Hardening-Soil soil constitutive model is adopted, and the safety factor of the foundation pit is considered to be anti-heavy. The pair of external wall insertion ratio λ and pit toe coefficient α is analyzed The influence of the stability coefficient of the foundation pit reveals two instability failure modes of the foundation pit in the pit. The results show that when λ >0.25 or α <1.5, when the inner and outer foundation pits lose stability, a continuous arc sliding surface is formed, and it is safe and stable. The coefficient increases with increasing and decreasing,but when α<1.0, the decrease in the width of the outer pit platform will reduce the sliding arc surface, reduce the passive soil range of the anti-sliding soil body, and reduce the safety factor;λ< When 0.25 or α>1.5, the uplift damage point of the foundation pit appears at different positions of the inner and outer pits, and the inner and outer foundation pits can be regarded as two independent foundation pits for stability checking. The research results can provide reference for the stability calculation and support of the pit in the pit.

关 键 词：基坑工程 坑中坑 抗隆起稳定系数 失稳破坏模式 外墙插入比 坑趾系数 

分 类 号：TU463[建筑科学—结构工程]