珠江特大桥承台基坑突涌事故处理降水设计与施工

Dewatering Design and Implementation for Treatment of Water Kick-in at A Bridge Cap Foundation Pit in the Pearl River

摘要:

珠江一特大桥主墩位于珠江水域中，承台基坑施工采用锁口钢管桩围堰围护， C30水下混凝土封底。封底完成后进行围堰内排水时，基底承压水击穿了封底混凝土，造成了基底突涌事件。对比在围堰内降水和在围堰外降水两种方案后，决定采用围堰外降水的方法，将承压水位降至封底顶面以下。该方案工期短、费用低，开创了在珠江内降底承压水的先例，成功处理了围堰封底失败的事故，确保了承台的顺利施工。实践证明在深水中降承压水是可行的，降水是保证承台基坑安全的重要手段之一，为类似工程提供了宝贵的经验。

Abstract:

The main pier of a large bridge is located in the Pearl River. Locked steel pipe piles were used as the enclosure structure for the cushion cap foundation pit of the main pier, with C30 underwater concrete used for bottom-sealing. After bottom-sealing was completed, the confined water level was too high, leading to water kick-in at the bottom of the foundation pit during the cofferdam drainage process. Two solutions were discussed afterwards: the first option was internal dewatering of cofferdam and the second was external dewatering of the cofferdam. After comparison, the second solution was chosen. External dewatering of the cofferdam eliminated successfully the incident and ensured the smooth construction of the pile cap, proving that it is feasible to lower the confined water level in the river. Dewatering is one of the important means to ensure the