大直径基桩坍孔处理施工技术

Construction Techniques for the Treatment of the Collapse of Bored Holes for Large-Diameter Foundation Piles

新月铁路分离式立交桥21-1基桩紧邻电气化铁路,振动较大且砂土层较厚,在试桩过程中发生坍孔。分析工程具体情况,决定采用预制钢筋混凝土沉井护壁处理。介绍了沉井的设计、加工与下沉,大直径冲击钻成孔过程及相应的质量控制措施,处理后的基桩质量良好。可为类似工程处理提供有益借鉴。

Owing to the fact that the No. 21-1 foundation pile of the Xinyue Railway Separate Overpass is near an electrified railway, where the vibration is very strong and the sand layer is thick, the wall of the bored hole collapsed in the course of test-boring the foundation pile hole. Upon the basis of analysing the specific conditions of the project, the technical scheme of maintaining the wall of the bored hole with pre-cast reinforced concrete protective caisson is decided to be adopted for the treatment of the collapse of the hole wall. The design, processing and sinking operations of the caisson are introduced in the paper, with the boring process of the hole with a large-diameter impact drill and the corresponding quality-control measures presented. After the treatment, the foundation pile ＂is found to be of good quality. This paper may serve as a useful reference for the treatment of other similar projects.