某水闸工程深基坑黏土围堰施工及降排水研究

Research on the Construction and Drainage of Deep Foundation Pit Clay Cofferdam for a Sluice Project

广东某水闸工程挖掘建设了深基坑。在这些地层中,有两个封闭的含水层,其中一个含水层部分缺失。为保证基坑开挖的安全性,坑底所在的上边界蓄水层的测压头应低于坑底1m,而下边界蓄水层的测压头应排水至安全水位,以避免隆起问题。大堤距离基坑较近,应控制排水引起的变形。进行了排水试验,获得了上部耐压含水层的渗透系数。分析计算得到的渗透系数平均值为20.45 m/d,高于数值模拟得到的值(水平渗透系数K=16 m/d,垂直渗透系数Ky=8 m/d)大。K和Ky之间的差异表明含水层的各向异性。为施工设计了两种排水方案,并通过数值模型进行模拟,以进行比较。结果表明,虽然第一种方案能够满足需求,但最大累积沉降和不均匀沉降为94.64mm和3.3%。分别超过了限定值。同时,第二种方案将B匝道和A匝道河岸的防水帷幕底部安装在海拔-28m的上游,并沿堤防设置27口补给井,可以显著控制堤防的变形。

A deep foundation pit was excavated and constructed for a water gate project in Guangdong.In these formations,there are two enclosed aquifers,one of which is partially missing.To ensure the safety of foundation pit excavation,the pressure head of the upper boundary aquifer at the bottom of the pit should be 1m lower than the bottom of the pit,while the pressure head of the lower boundary aquifer should be drained to a safe water level to avoid uplift issues.The embankment is relatively close to the foundation pit,and deformation caused by drainage should be controlled.Drainage tests were conducted to obtain the permeability coefficient of the upper pressure bearing aquifer.The average permeability coefficient obtained through analysis and calculation is 20.45m/d,which is higher than the numerical simulation values(horizontal permeability coefficient K=16m/d,vertical permeability coefficient Ky=8m/d).The difference between K and Ky indicates the anisotropy of the aquifer.Two drainage schemes were designed for construction and simulated using numerical models for comparison.The results indicate that although the first solution can meet the requirements,the maximum cumulative settlement and uneven settlement are 94.64mm and 3.3%,respectively,exceeding the limit values.At the same time,the second plan installs the bottom of the waterproof curtain on the banks of Ramp B and Ramp A at an altitude of -28m upstream,and sets up 27 supply wells along the embankment,which can significantly control the deformation of the embankment.