特大圆形深基坑施工技术

武汉阳逻长江公路大桥南锚碇特大深基坑是目前国内最大的圆形深基坑。采用了圆形地连墙和变厚度内衬做支护结构，采用墙下灌浆帷幕和墙外自凝灰浆防渗墙作为封水系统，采用由砂桩和坑内外降水井组成的排水系统进行降水减压。基坑采用“岛式开挖”，按照“对称、分区、平衡、限时”的原则进行开挖。采用了信息化施工工艺，用基坑支护结构的内力反演分析和变形多步滚动预测成果判断和预测基坑的安全性。上述技术措施确保了基坑施工的安全。

Bracing Technique of a Super Round Pit Excavation

The south anchorage of Wuhan Yangluo Yangtze River Highway Bridge is the largest and deepest round Pit being built in China. A ring diaphragm wall accompanied with varied-thickness inner concrete lining acted as the bracing system, a grouting curtain beneath the diaphragm wall along with a self-setting cement-slurry water-tight wall around the pit composed a water-resistant system, and sand drains and dewatering wells functioned as a drainage system. "Island excavation" is conducted according to such principles as symmetry, zoning, equilibrium and time limiting. Information-guided excavation technique was used, that is to judge and predict the safety of the excavation with conversed endogenetic forces and poly-phase predicted deflection of the bracing system. These techniques guaranteed the safety of the excavation.