中文摘要：

采用土体卸载条件下的塑性有限元模型,以苏州某地铁换乘站坑中坑为基本模型,系统研究了坑趾系数α对粉土坑中坑基坑支护结构内力的影响。结果表明,α变化对内外坑支护结构深层部位内力影响较为显著。外墙最大正负弯矩、最大正负剪力随α增大而减小,最大正负弯矩作用位置上升,外坑第三道支撑轴力随α增大急剧减小约30%左右;内墙最大负弯矩随α增大而减小,最大正弯矩却随α增大而增大,但最大正弯矩不到最大负弯矩的1/3,最大正负弯矩位置随α增大而上升,最大正负剪力均随α增大而减小,内坑第二道支撑轴力则随α增大显著减小。坑趾系数α变化对坑中坑深层土体应力场产生影响,当α超过0.75时影响趋于减缓。

英文摘要：

The plastic finite element model is used based on soil unloading conditions,the influence of the external wall insertion ratioαon the retaining structure and the deformation of the excavation are studied based on the basic model of the pit of a metro transfer station in Suzhou subway line.The results show that variation ofαhas significant impact on the internal force of the deep support structure.The maximum positive and negative bending moment and the maximum positive and negative shear force of the external wall decrease withα,and the working position of maximum positive and negative bending moment rise,the third supporting axial force of the outer pit drops significantly by around 30% with increase ofα;the maximum negative bending moment for internal wall decreases with the increase ofα,but the positive bending moment increases with increase ofα,however the maximum positive bending moment is less than 1/3 of that for negative bending moment.the positions of maximum positive and negative bending moment rise with the increase ofα,and the maximum positive and negative shear force reduce with the increase ofα,and especially the second support axial force is reduced significantly with increase ofα.variation ofαhas impact on the stress of deep earth of pit-in-pit,and whenαexceeds 0.75,the impact becomes gentle.