深基坑内撑式支护结构综合刚度研究

Research on synthetic system stiffness of strutted retaining structure for deep excavation

基于Clough系统刚度,提出一种可综合考虑内撑式基坑围护墙、内支撑和墙后土体刚度的支护体系综合刚度表达式,以较好地预测基坑变形。将Clough支护刚度、Bolton支护刚度和文中综合支护刚度应用于天津地铁6号线22个基坑工程469个围护墙测斜案例中,结果表明,基坑围护结构最大变形随着无量纲综合支护体系刚度(η?)的增大而减小,当η?增大到一定值后,其变形值趋于恒定。进一步分析土体不排水抗剪强度调动率,得到天津地铁6号线地铁基坑墙后土体调动率不大于0.6,远小于上限值0.8,说明天津地铁基坑建设具有足够的安全储备。研究成果可为同类工程经济性和安全性设计提供借鉴。

Based on Clough system stiffness model, this paper introduces a novel synthetic stiffness expression of strut system for excavation. This expression considered the wall stiffness, strut stiffness and the soil stiffness behind the wall, and thus it had substantial advantage to predict the deformation induced by excavation. Clough system stiffness, Bolton system stiffness and the synthetic system stiffness proposed in this paper were applied to measure the tilt of 469 retaining walls in 22 deep excavations of Tianjin subway line 6 engineering. The maximum deformation of the retaining structure in foundation pit decreased with the increase of the stiffness 17＇ of the dimensionless composite support system. The deformation value tended to be constant, until 77＇ increased to a certain value. When the mobilized undrained shear strength ratio of soil was further analyzed, it is found that the ratio of the soil behind the wall along Tianjin subway line 6 was less than 0.6. The upper limit value of this ration is 0.8, which indicates that the excavation engineering of Tianjin subway line 6 has sufficient safety reserves. Therefore, research results can provide significant reference for the economic and safety design of similar engineering.