单井点和单排井点布置的真空降水现场试验及比较研究

研究单井点和单排井点真空降水条件下,地层中地下水水位和抽水流量,在重力场和真空压力场耦合作用下的变化过程,并进行比较分析。试验表明,对于单井点排水条件,随着真空负压力和抽水井深度的增大,水位的下降有一定增加,而离开抽水井点较远处的水位下降更为明显。单排井点布置条件下,随着抽水井深度和抽水井间距的增大,无论是抽水井点布置方向还是垂直于抽水井点布置方向的地下水位的下降深度将有明显增大,而沿抽水井布置方向的水位下降深度更为显著。此外,在多次反复降水条件下,后续降水过程中地下水位的下降速率将有增快的趋势。试验还表明,抽水井井口的负压力小于真空泵出水口处的负压力,损失量可达12.5%,因此,在进行真空降水设计时需要考虑出水管道的长度。

Field tests comparative study of vacuum well-point dewatering under a single well-point or a single row well-point

Based on the field tests of vacuum well-point dewatering, the evolutions of groundwater level and the variations of the water flow in silt ground layer are studied under combined gravitational and vacuum negative pressure, which include both the cases of a single well-point and a single row well-point. Test results show that, for the condition of a single well, the declining depths of groundwater level increase with the increase of vacuum negative pressure and the depth of drainage well, and the declines of groundwater level at the points away from the drainage well will be more obvious. For the condition of a single row well-point, with the increase of the depth and space of drainage wells, the declines of groundwater level are also very apparent whether along the direction of well-point arrange or in the perpendicular direction of well-point arrange; and the former is more obvious. On the other hand, the declining ratio of groundwater level has an increasing trend after several repeated dewatering processes. Besides, the vacuum pressure in the mouth of a well is lower than it in the water outlet of vacuum pump with a loss of approximately 12.5%, which indicates that the length of the pipeline of water outlet should be considered in the design of vacuum well-point dewatering in practice.