强富水厚层砂卵石深基坑突水三道防线技术研究

Study on three passes preventing water inrush for strong rich water and thick sandy pebble deep foundation pit

长沙地铁1号线省政府车站基坑长464.6m,深20m,宽20.7m.坑址范围分布超过40m深厚层砂卵石,富水性强,基坑内、外水头大,渗透系数大,地下连续墙难以穿越该地层,开挖过程中突水风险高,极易基坑底突涌.提出了多道防线预防基坑突水理念,采用三道防线综合技术(即合理增加地下连续墙深度、袖阀管法加固基坑地层和疏降水技术),预防基坑突水,加强施工监测.监测结果和工程实践表明:综合方法防基坑突水是有效的,该工程基坑突水综合预防方法对类似工程具有重要参考价值.

The foundation pit of provincial government station,Changsha metro Line 1 is 464.6 m long,20 m deep and 20.7 m wide. There is strong rich water more than 40 m deep sand pebble which is big permeability coefficient and high water head between side and outside of foundation pits and is hardly penetrated by the underground continuous wall. So the water inrush risk is extremely high, and the pit bottom water inrush possi- bly happens during the foundation pit excavation. The multi-channel lines idea of pre- venting foundation pit water inrush is suggested. And specifically, the comprehensive three channel lines prevention method of the foundation pit water inrush is finished. This method includes the rational increase of underground continuous wall, sleeve valve barrel grouting method for reinforcing the foundation pit strata, drainage and dewatering tech- nology and strengthening foundation pit monitoring. The monitoring results and engi- neering practice show that the comprehensive water inrush prevention method is effec- tive. And this method can be as an important reference for similar construction.