软土地层盾构工作井基坑支撑轴力异常分析

ANALYSIS OF ABNORMAL SUPPORTING AXIAL FORCE OF FOUNDATION PIT FOR SHIELD WORK SHAFT IN THE SOFT CLAY

依托杭州配水工程某盾构工作井,对其开挖过程中的支撑轴力进行监测分析,探究其第一、三道混凝土支撑轴力异常的原因,同时结合有关支撑轴力异常的工程案例,通过钢筋混凝土支撑轴力计算公式分析导致轴力异常的影响因素。结果表明支撑轴力受相邻土层开挖的影响最大,轴力值在该阶段增长较快,可增长到整个开挖期间实测轴力最大值的75%以上;基坑在设计时需注意到基坑的空间效应影响,针对钢支撑和混凝土支撑、角撑和对撑采用不同的轴力设计值,做到同时满足工程的安全性与经济性,减少不必要的浪费;初始频率fi0、温度变化△T、混凝土的膨胀收缩和徐变都是导致支撑轴力异常的因素,基坑设计时需综合考虑这些因素。

Base on one shield work shaft in Hangzhou,this paper is monitoring and analyzing the strut axial forces during the excavation process,exploring the abnormal reason of its first and third concrete strut axial forces,and combining with engineering project about abnormal supporting axial forces.With the formula for computing the reinforced concrete strut axial forces,this paper analyses influence factors that lead the axial force to abnormal.The results show that the supporting axial force is most affected by the excavation of adjacent soil layer,and the value of axial force increases rapidly in this stage,which can increase to more than 75%of the measured maximum axial force during the whole excavation period.During the design process of the foundation pit,it is necessary to pay attention to the spatial effect of the foundation pit,and adopt different axial force design values for steel strut and concrete strut,angle strut and pair strut,to guarantee the safety and economy of the project and reduce unnecessary waste.Finally,Initial frequency fi0,temperature change△T,expansion,shrinkage and creep of concrete are all factors that lead to the abnormal axial force of strut,which should be taken into consideration during the design process.