岩溶及断层破碎带地层基坑设计与坑底突涌治理

Study on optimization design and inrushing control technology for deep-foundation pit in karst and fault fracture zone

在南京某地铁站岩溶及断层破碎带地层开挖深基坑时,由于断层破碎带和地连墙局部嵌固深度不足引起坑底突涌水事故,进而导致基坑变形,对周边环境产生一定影响。在综合分析施工风险和突涌水事故原因的基础上开展围护结构优化设计和突涌水治理。将原设计方案中的第4、第6道钢支撑变更为钢筋混凝土支撑,在有问题的格构柱基础桩外围施打微型钢管桩进行补强;选用凝固时间更快、抗水分散性更好的新型注浆材料GT-1,采用前进式分段注浆和模袋封孔注浆新工艺。通过后期检验,证明围护结构优化设计和坑底突涌水治理效果显著。

In excavation of a deep foundation pit in Karst and fault fracture zone in Nanjing,because of the fault fracture zone and local insufficient depth of diaphragm wall,pit gushing accidents occurred,which resulted in deformation of the foundation pit and a certain impact on the surrounding environment. Based on comprehensive analysis of construction risk and gushing water accident,the optimal design of retaining structure and the treatment of water bursting were carried out. The fourth and sixth steel support in the original design were replaced by concrete support,and micro steel pipe pile was applied to reinforce several weak lattice column foundation pile; a new grouting material with faster solidification time and better water dispersion resistance called GT-1 was selected. Two types of new technologies,advancing staged grouting and membrane bag sealing,were adopted.Through later inspection and data monitoring,we found that the effect of retaining structure optimization and pit inrushing-control measures were obvious. The research results can provide technical guidance and theoretical basis for similar projects in the future.