明挖异形基坑下穿高架桥及近接航站楼施工的影响与控制

Construction Impact and Control of Open-excavation Irregular Shape Foundation Pit under-passing Viaduct Bridge and Adjoining Terminal Building

为研究明挖异形基坑施工对近临既有结构的施工扰动影响与控制效果,以南宁空港枢纽联络通道基坑工程为例,针对明挖异形深基坑下穿机场出发层高架桥和近接航站楼的施工问题,采取有限元数值模拟和现场监测相结合的方法,研究了复杂环境下基坑开挖引起的围护结构及其周边建筑物的施工扰动效应及变形特征。在此基础上,提出了基坑非同步分层、分区和分块开挖的方案,以及采取人工挖孔桩作为局部围护结构的施工控制措施,最终使得明挖异形基坑顺利开挖并实现对周边建筑物变形的有效控制。研究结果显示:基坑开挖后的桥梁呈现东边沉、西边隆的形态;周边地面沉降量排序为中间段地面沉降量>基坑南端地面沉降量>基坑北端地面沉降量>基坑北端放坡段沉降量,与数值模拟结果中的桥梁桩基差异沉降规律一致。

The foundation pit engineering of Nanning Airport Hub connecting passage is taken as example to study the influence of open-excavation irregular shape foundation pit on the adjacent existing structure and control effect.Targeting the engineering problem in the open-excavation irregular shape deep foundation pit under-passing airport departure level viaduct and the construction adjoining terminal building,finite element numerical simulation and on-site monitoring are combined to study construction disturbance effect and deformation characteristics of the enclosure structure and the surrounding buildings caused by foundation pit excavation in complex environment.On this basis,the scheme of asynchronous layered excavation,subdivision excavation and blocked excavation of the foundation pit,the construction control measures for using manually excavated piles as the local enclosure structure are proposed.The final open-excavation irregular shape foundation pit is constructed smoothly,and the deformation of surrounding buildings is effectively controlled.Research results show that the bridge after foundation pit excavation presents morphology of sinking in the east and heaving in the west,the surrounding land subsidence is sorted to be middle section>south end>north end>north end grading section.The differential settlement law of bridge pile foundation in the numerical simulation results is consistent.