弱透水地层条件下基坑降水试验研究分析

Analysis on Dewatering Test of Foundation Pit in Stratum with Small Permeability

地铁基坑开挖过程常会遇到渗透性很小的粉质粘土层,普通管井降水技术无法对其进行有效疏干,残留水会对基坑安全造成重大影响。基于此,文章采用降水试验和数值模拟对管井降水和真空管井降水技术进行了研究。结果表明,真空管井降水条件下涌水量是管井降水的1.1~1.4倍,降水时效明显,有利于缩短工期;真空管井降水条件下降深是管井降水的1.2~1.6倍;地层降水浸润线更加平缓,降水影响半径明显增加,利于增加井间间距,经济效益明显。

It is often to encounter silt clay with small permeability during excavation of metro foundation pit, and difficult to dewater effectively with tube well method, the residual water could significantly affect the safety of foundation pit. Dewatering test and numerical simulation were conducted to study the dewatering techniques by tube well and vacuum tube well. The results show that the volume of water inflow in condition of vacuum tube dewatering is 1.1-1.4 times larger than that of tube well method, with obvious time effect and shorter construction period;the drawdown in condition of vacuum tube well is 1.2-1.6 times larger than that of tube well method;the phreatic line of dewatering is more flat and the affected radius of dewatering increases significantly, which is favorable to increase interval of dewatering wells and obtain good economic benefit.