天津首例基坑工程承压含水层回灌实测研究
Field observation of artificial recharge of confined water in first excavation case in Tianjin
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摘要: 通过开展天津某基坑工程抽水试验,观测到场区第一、二承压含水层间有一定水力联系。而基坑止水帷幕并未截断第二承压含水层,为防止或减小坑内降水引起的坑外重点保护建筑的沉降,将基于沉降控制的回灌技术运用于该基坑工程中,在被保护建筑四周布置5口回灌井进行承压层回灌。现场监测资料表明,回灌井运行正常,回灌速率稳定,对埋深24~46 m的第一、二承压层的单井自然回灌量为24~72 m3/d,回灌过程中承压层最大水位抬升约6 m,且承压含水层水位升降与被保护建筑物隆沉之间呈现出很强相关性和同步性。本次回灌是天津市首个在基坑工程中开展基于沉降控制的承压含水层回灌的成功案例。Abstract: By carrying out in-situ pumping tests in an excavation of Tianjin, hydraulic connection between the first and second confined aquifers is observed. Because the second confined aquifer isn't cut off by waterproof curtain, to reduce or eliminate the settlement of the key protected buildings induced by dewatering, the artificial recharge is applied during the process of excavation and dewatering in the pit. Five recharge wells are arranged around the protected buildings to recharge the confined aquifer using the urban water. The in-situ monitoring results show that the water volume recharged by a single recharge well can reach 24 m3/d to 72 m3/d and the water head can be raised as much as 6 m. The measured settlement of the buildings during excavation further shows that the variation of the settlement of the protected buildings almost simultaneously and directly relates to the fluctuation of the head of confined aquifer. It’s the first successful case of recharge of confined water in an excavation in Tianjin based on settlement control.