不同支撑形式下基坑受力变形特征对比研究

Comparative Study on Foundation Pit Deformation Under Different Support

为了总结分析地铁车站基坑分段应用不同支护形式的变形控制效果,依托北京地铁27号线上清桥站基坑工程,对车站原设计的“一混凝土+四钢”混合支撑和局部优化后的全钢支撑基坑断面的变形监测数据进行了统计分析。研究表明:2种支撑形式的地表沉降槽存在一定差异,但混合支撑对地表沉降控制效果较好;地连墙呈现刚性变形特征,墙体以第1道混凝土支撑为支点呈现旋转变形进而导致混凝土支撑上部墙体向坑外移动;混合支撑区第1道混凝土支撑轴力最大,而钢支撑区第2道钢支撑轴力最大,且第1道的支撑轴力在第2道支撑架设前后呈现线性增长—应力松弛—基本稳定的规律。由变形监测数据可知,混合支撑对基坑变形的控制效果要优于全钢支撑。

In order to summarize and analyze the deformation control effect of different supporting forms applied in different foundation pit sections of subway station,based on the foundation pit project of Shangqingqiao Station of Beijing Subway Line 27,the deformation monitoring data of the original design of"one concrete+four steel"mixed supporting and all-steel supporting after partial optimization of the foundation pit section were analyzed statistically.The results show that there are some differences in surface settlement trough between the two types of support,and the mixed support has better control effect on the surface settlement.The diaphragm wall presents the characteristics of rigid deformation.Taking the first concrete support as the fulcrum,the wall rotational deform which cause the the upper wall of the concrete support to move out of the pit.The axial force of the first concrete strut is the largest in mixed strut area,while that of the second steel strut in steel strut area is the largest.The axial force of the first strut before and after the erection of the second strut shows a linear growth-stress relaxation-basically stable law.According to the deformation monitoring data,the control effect of mixed supporting is better than that of all steel supporting.