水库防渗措施及坝后排水沟距离对周边农田地下水埋深的影响  

Influence of reservoir seepage prevention measures and drainage ditch behind dam on groundwater depth of surrounding farmland

作　　者：毛海涛[1] 王正成[1] 王晓菊 黄庆豪 刘阳[3] 

机构地区：[1]重庆三峡学院土木工程学院,重庆404100 [2]河海大学环境学院,南京210098 [3]新疆农业大学水利与土木工程学院,乌鲁木齐830052

出　　处：《农业工程学报》2017年第11期98-107,共10页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金项目(51309262);重庆市科委基础与前沿研究计划项目(cstc2015jcyj A0300;cstc2015jcyj A00022);重庆市教委科学技术研究项目(KJ1601024);重庆三峡学院校企合作项目(16PY03)

摘　　要：干旱区平原水库渗漏对下游农田土壤的水盐动态变化影响较大,易造成土壤的次生盐渍化和沼泽化。水库常采用"上防下排"措施来降低坝后农田地下水埋深,但排水沟参数如何选择,与坝基防渗体如何联合使用,治理效果如何等都值得深入研究。该文基于非饱和土体渗流理论,以恰拉水库周边农田为研究对象,针对"上防下排"措施进行数值模拟,分析恰拉水库采用水平铺盖、悬挂式防渗墙或无防渗措施时,坝后农田地下水埋深与坝后排水沟位置及深度的关系,并针对下游坝坡稳定及坝后积水进行分析,并通过田间试验进行验证。研究表明:在不同的渗流控制方案下,农田地下水埋深均以排水沟中轴线为对称轴呈现"漏斗形"降落趋势,排水沟前地下水埋深逐渐增大,排水沟后的地下水位有一小幅度的减小,因此,"上防下排措施"从"源头"处减小渗水进入坝后农田,增大农田地下水埋深。3种方案对比显示,不同"上防下排"渗流控制方案在遏制水库渗漏和减小坝后农田地下水的效果不同。悬挂式防渗墙和无防渗体工况不能有效减小水库的渗漏量,联合排水沟使用效果较差。22倍水头的水平铺盖在渗流控制方面优于悬挂式防渗墙和无防渗体时的工况,联合坝后排水沟及时排水后,可有效的将地下水埋深控制在2.72 m左右,大于当地的地下水临界水位2.45,有效遏制坝后土壤的盐渍化趋势。排水沟设置的位置和深度对大坝稳定存在一定影响,计算实际工况(22倍水平铺盖)时下游坝坡抗滑安全系数为1.358,大于下游坝坡最小抗滑安全系数1.242,下游坝坡处于安全状态。排水沟设置后,坝趾至沟间的积水长度是产生坝后沼泽化的主要原因。计算和实测实际情况下的积水长度为0.27 m,沼泽化面积较小。此外,计算还发现避免农田沼泽化对应的排水沟最小深度为5.18 m,实际工程中排水沟深度为6 m,可�Reservoir leakage has a great influence on water-salt dynamic,which is easy to cause soil secondary salinization and swamping in arid area.Groundwater depth of farmland behind dam is reduced by anti-seepage body and drain measure usually.Drainage ditches are set up behind dam,which can cut off seepage water and discharge water,therefore reducing the leakage loss.But how to choose parameters of drain,how to be combined with impervious body,and so on,these questions need to be studied further.Based on unsaturated soil seepage theory,aimed to the farmland around Qiala Reservoir,this paper calculated the combination measures by numerical simulation,and analyzed the relationship between groundwater depth and depth and position of drainage ditch by vertical cutoff wall,horizontal impervious blanket or non anti-seepage measures.Besides,we analyzed the downstream slope stability and adopted the field experiment to validate it.This research showed that the buried depth of farmland groundwater is characterized by a ＂funnel-shaped＂ downward trend taking the central axis of drainage ditch as a symmetrical axis in different seepage control schemes.The groundwater depth increased gradually before the drainage ditch,and decreased a little after the drainage ditch.Therefore,the ＂anti-seepage body and drain measure＂ reduce seepage into the farmland from the source,which can make farmland maintain a low groundwater depth.Different seepage control schemes of ＂anti-seepage body and drain measure＂ were different on the curbing and the effect of reducing the leakage of reservoir to farmland.The hanging cutoff wall and the non-impervious body cannot reduce the leakage of the reservoir effectively,and we found the combination of the former 2 ways has a weaker effect on anti-seepage.By comparing the 3 schemes,it was considered that the horizontal impervious blanket with a length of 22 times water head was better than the suspended cutoff wall and non-impervious body in seepage control.After combining it with the drainage ditc

关 键 词：地下水 土壤 模型 土地盐渍化 水平铺盖 排水沟 

分 类 号：TU640.32[建筑科学—建筑技术科学]