土岩组合地区基坑开挖对扩展基础桥墩沉降影响研究

Study on influence of foundation pit excavation on settlement of spread foundation piers in soil-rock combined area

针对在建基坑工程对既有桥梁造成影响的问题,依托徐州土岩组合地区某地铁基坑工程,通过研究软土地区基坑开挖墙后地表沉降预测理论,推导出该工程的墙后地表沉降曲线。通过Midas数值软件模拟与现场监测综合分析的方法,研究了基坑开挖对墙后地表和扩展基础桥墩造成的沉降影响。研究表明:在整个开挖过程中,基坑周边地表沉降曲线呈"勺形"分布,第三层土体开挖对地表沉降的影响最大;桥墩与相同位置地表在各开挖阶段的沉降量分别占其最终沉降量的比例基本一致;基坑开挖对桥墩造成的倾斜角度会随桥墩下卧土体沉降曲线的变化而变化,桥墩受基坑开挖造成的沉降影响会随其基础埋深的增加而减弱。该研究可为类似工程设计和施工提供参考。

Excavation of foundation pit can influence the safety of existing bridge,based on a subway foundation pit project in the soil-rock combined area in Xuzhou,the settlement curve of ground surface behind retaining wall is derived based on the ground surface settlement prediction theory. The ground surface settlement behind the retaining wall and the settlement of spread foundation piers after excavation of the foundation pit has been analyzed by Midas numerical simulation software and field monitoring. The research results indicate that：during the whole excavation process,the surface settlement curve of the foundation pit is ＂spoon-shaped ＂distribution,and the third layer excavation has the greatest influence on the surface settlement,the pier settlement and the corresponding surface settlementafter each excavation are account for a some proportion of the final settlement; the angle of inclination of the pier caused by the excavation of foundation pit varies with the settlement curve of the soil below the pier,and the pier settlement reduces with the increase of the foundation burial depth. This research could provide reference for similar engineering design and construction.