防-截-排系统对平原水库坝后地下水位的影响

针对干旱区平原水库渗漏引起的坝后土壤盐渍化问题及防治措施,以恰拉水库为例,基于非饱和渗流理论,运用ABAQUS有限元软件模拟水库在不同防渗措施与截排水系统的联合作用下对坝后地下水埋深的影响。结果表明:通过"上游防渗、下游截排"的形式可以有效的降低坝后农田地下水位,防治土壤发生次生盐渍化。相比无防渗和水平铺盖措施,垂直防渗措施结合截排水系统更能有效地将下游渗流稳定区的地下水位埋深控制在2.67 m,大于周边农田的"临界埋深"(2.45 m)。防渗措施与截水沟的联合作用重点解决了坝后渗漏水的"来源"问题,而排水系统不但可以保证截水沟控渗效果的持续性,还可以解决渗漏水的"去向"问题——坝后截排水系统与农田渠系的结合使坝后渗漏水用于农田灌溉,最终实现了坝后控渗、治理土壤盐渍化体系与农田灌溉体系相结合的理念。

Effect of anti-seepage-water interception-drainage system on groundwater level behind dam of plain reservoir

Aiming at the problem of soil salinization behind dam caused by the leakage of the plain reservoir in arid region and its prevention and control measures，the joint-effects from different anti-seepage measures and water interception-drainage systems on the buried depth of groundwater behind the dam of plain reservoir are simulated in accordance with the unsaturated seepage theory by means of the ABAQUS finite element software through taking Qiala Reservoir as the study case． The study result shows that the groundwater level of the farmland behind the dam can be effectively lowered through the mode of upstream anti-seepage and downstream interception，and then the secondary soil salinization can be prevented． Compared with the measure without anti-seepage treatment and the horizontal impervious blanket，the buried depth of the groundwater level within the downstream stabilized seepage zone can be effectively controlled to 2. 67 m，which is larger than the critical buried depth of 2，45 m in the surrounding farmland，by a vertical anti-seepage measure combined with water interception-drainage system． The joint-effect from anti-seepage measure and intercepting ditch mainly solves the problem from the“source”of the leakage water behind dam，while drainage system can not only ensure the persistence of the seepage control effect from intercepting ditch，but also can solve the problem of the “destination”of the leakage water—the combination of the water interception-drainage system behind dam with the farmland canal system makes the leakage water be used to farmland irrigation，thus finally realizes the concept of combining the anti-seepage control behind dam and soil salinization control system with farmland irrigation system．