潜水回水初始阶段的定性半定量分析及对水跃成因的解释

摘要

文章提出并采用水力坡度分析方法，对潜水回水初始阶段进行了定性半定量分析，为了解潜水回水过程提供了新的视角。通过分析潜水回水初始时刻的水力坡度，河渠侧的界面被分为2段：河间潜水位之上的铅直段和之下的水平段。水平段上点的水力坡度最大且相等，方向为水平向右；铅直段上点的水力坡度方向趋于铅直向下，越向上水力坡度越小。经过微小时间段Δt 后，水力坡度均相应变小，铅直段相邻点间地下水运动发生冲突，水力坡度方向由趋于铅直向下向右偏转。将水力坡度分析方法用于分析潜水井流的过程和特征，水跃的成因可解释为：在相同水力坡度和过水断面面积下，井内大空间水流速度远大于孔隙中的潜水流速度，井内水位急速下降，从而形成水跃；水跃越大，进入井内的流量就越大。%We use hydraulic gradient method to analyze the initial unconfined aquifer’s recharging from streams qualitatively-semiquantitatively thus provide a new visual angle for recharging process.Analysis of the hydraulic gradient of initial recharging,the left stream interface is divided into two segments,the vertical segment and the horizontal segment above and under the water table in the inter-stream area.The hydraulic gradient of the points in the segment is maximum and equal.It is to right in the horizontal direc-tion.The hydraulic gradient of the points in the vertical segment tends downward in the vertical direction and it gets smaller upward.After a tiny period,the hydraulic gradients of any point become smaller,wa-ters coming from adjacent points in the vertical segment collide,and the direction of the hydraulic gradient is deflected to the right.The qualitative-semiquantitative analytical method can also be employed to ana-lyze unconfined radial flow to a pumped well.Presence of a seepage face can be explained in the way:un-der same hydraulic gradient and cross-sectional area,the flow velocity in big space of the well is much greater than in the pore.The water level in the well rapidly declines thus a seepage face is developed.The higher the seepage face is,the greater the rate of discharge into the well is.