临近铁路坑中坑偏载基坑开挖支护结构受力与变形规律研究

Study of Deformation Rules and Stress of Retaining Structure of Unsymmetrically Loaded Foundation Pit in Another Foundation Pit Adjacent to Railway

为了研究坑中坑偏载基坑开挖支护结构性状,以某临近铁路的坑中坑基坑工程为依托,基于实测数据分析基坑的变形规律,并运用有限元软件对不同的设计方法进行计算分析。实测表明,坑中坑偏载基坑的超载侧墙体变形呈悬臂形,而欠载侧墙体上部为朝向坑外的逆向位移,下部朝向坑内位移。有限元分析表明:忽略边坡开挖过程将边坡等效为分布荷载进行计算,将高估超载侧墙体内力,低估欠载侧墙体内力和第1道支撑轴力;按超载侧荷载进行对称计算将高估欠载侧围护结构内力;建议坑中坑偏载基坑支护结构设计考虑基坑整体性状和外坑开挖对内坑围护结构内力的影响,对两侧围护结构区别设计。

Different design methods for retaining structure of unsymmetrically loaded foundation pit in another foundation pit adjacent to railway are calculated and analyzed by finite element software;and the deformation rules of the retaining structure are analyzed based on monitoring data.The monitoring data show that：1 ）For overloaded sidewall,the deformation of the sidewall increases with the excavation depth increases and moves towards inner foundation pit.2）For underloaded sidewall,the deformation of upper part faces to outer foundation pit and that of lower part faces to inner foundation pit.The finite element analysis results show that：1 ）The internal force of overloaded sidewall would be overestimated and the internal force of underloaded sidewall and the axial force of Support No. 1 would be underestimated when the slope excavation is ignored and the slope is equivalent to distributed load.2）The internal force of retaining structure of underloaded sidewall would be overestimated when calculation is based on overloaded sidewall. 3）The integral characteristics of unsymmetrically loaded foundation pit in another foundation pit and the interaction between two foundation pits should be considered in design phase of the foundation pit.