土岩组合地层深基坑桩撑体系变形及受力分析

以青岛地铁1号线胜利桥站施工为工程依托,对土岩组合复杂地质条件下深基坑开挖过程中围护结构桩撑体系的变形及受力特性进行研究,采用现场监测数据分析和有限元软件建模分析方法,研究上软下硬地层条件下基坑开挖土体受力及变形分布规律和基坑围护结构变形规律及受力机理.得出的结论:①桩体位移峰值位置随开挖过程不断下移,且围护桩桩体变形随着开挖进程由向坑内前倾逐渐变为")"形曲线变化;②当围护桩单独受力时,围护桩产生明显的嵌固段,桩身在嵌固段与土体交界处产一段2～3m的应力集中区域;③剪应力值不断增大,坑内土体形成塑性区,土体位移场的分布规律与圆弧滑裂面十分相似;④支撑为基坑围护结构的主要受力构件,当前一道支撑受力时,每次的位移增量逐渐减小,第四道支撑起作用时,位移增量仅为第三道支撑时的10％,说明桩撑体系协同作用对土体变形具有较强的控制作用.

Deformation and Force Analysis of Pile Foundation System of Deep Foundation Pit in Combination of Soil and Rock

Based on the differences in geological characteristics and calculation modes in Qingdao, the existing open-cut foundation pits have excessive deformation and excessive deformation. At the same time, the force-transmitting members that make up the foundation pit of the pile-support system are not matched. Based on the construction of Shengliqiao Station of Qingdao Metro Line 1, this paper studies the deformation and stress characteristics of the retaining structure pile-supporting system during the excavation of deep foundation pit under complex geological conditions of soil and rock, using on-site monitoring data analysis. The finite element software modeling and analysis method is used to study the force distribution and deformation distribution of foundation pit excavation under the condition of soft and hard stratum and the deformation law and force mechanism of foundation pit retaining structure. The conclusions are as follows: (1) The peak position of the pile displacement continuously moves down with the excavation process, and the deformation of the pile of the retaining pile changes gradually to the ")" curve as the excavation progresses forward toward the pit; (2) When the retaining pile is subjected to the force alone, the retaining pile produces a distinct embedded section, and the pile body produces a stress concentration area of 2 to 3 meters at the junction between the embedded section and the soil; (3) The shear stress value keeps increasing the plastic zone formed by the soil in the pit, and the distribution law of the displacement field of the soil is very similar to the arc-slip surface; (4) The main force-receiving member supporting the foundation pit retaining structure, when the current support is stressed, the displacement increment is gradually reduced each time, and when the fourth support is active, the displacement increment is only the third pass. 10% of the support, indicating that the synergy of the pile-support system has a strong control effect on soil deformation.