沟灌条件下灌水沟入渗特性研究

为探明沟灌时灌水沟的水分入渗规律,从沟灌二维入渗过程、入渗湿润锋运移特性、累计入渗水量变化过程、土壤含水量分布等方面研究了沟灌的入渗特征及其影响,研究表明:灌水沟中水深、沟底宽、湿周对沟灌入渗过程均有明显影响。沟中水深增大,有利于加大侧向入渗,垂向入渗减少,而水深减小,会加大垂向入渗,增加深层渗漏。灌水沟底宽不影响灌水沟的侧向入渗,仅影响垂向入渗,底宽减小,垂向入渗深度相应减小,且土壤表面以下40cm深以内水平向入渗深度平均值与最大垂向入渗深度的比值在沟底宽小时均大于沟底宽大时。合理的断面形式和大小有利于减小垂向入渗,加大水平侧向入渗,灌水沟断面形式为梯形断面时,宽深比近似为2效果最优。研究结果可为改进沟灌灌水技术提供参考。

基于湿润区分层假定对Green-Ampt模型的改进

假定入渗过程分为前期、后期两个阶段,入渗前期土壤饱和区与非饱和区厚度之比为一常数2β,非饱和区厚度随着入渗的进行而逐渐增大;入渗后期非饱和区的厚度不再随时间变化,为一定值,只有饱和区厚度随时间变化,基于此对Green-Ampt模型进行了改进。用传统Green-Ampt模型和改进模型对6组入渗测试资料进行拟合,传统模型拟合的相关系数为0.982(6组数据的平均值),相比传统模型,改进模型的拟合精度明显提高,相关系数提高了0.016,达到0.998(对应β=15);其中两组数据的效果尤为明显,相关系数分别提高了0.07和0.04,均达到了0.99以上。改进模型与传统模型同样具有较强的物理意义,但与传统模型相比,改进模型拟合得到的稳定入渗率更接近于测试值,具有更广泛的适用性。

Effect of particle size and grain composition on two-dimensional infiltration process of weathered crust elution-deposited rare earth ores

The two-dimensional infiltration experiment was carried out by means of digital image technology.The evolution process of the wetting body was described.The wetted front distance and the time show a very significant power function relationship.The horizontal wetted distance is larger than the vertical wetted distance in the initial stage.Then,the vertical distance of the wetted body gradually approaches to the horizontal distance.The infiltration distance decreases as the content of fine particles increases.The wetted front migration rate curve shows a three-stage change law,and it increases with the increase of coarse particle content.The directional velocity ratio is defined.The initial value of horizontal infiltration rate is larger than that of vertical one,and then the vertical infiltration rate is gradually close to the horizontal value.The empirical relationship between the characteristic particle size and the stable infiltration rate is established,which provides a theoretical basis for the prediction of the stable infiltration rate in in-situ leaching.

河岸侧向潜流水力交换过程试验研究

河岸侧向潜流水力交换对河流及其岸滩的生态健康有重要影响。为阐明河岸侧向潜流水力交换特征,基于室内二维砂槽模型试验,分析了潜流在沉积物中横向和垂向上的运动规律。研究结果表明,河岸侧向潜流运动主要受河水—地下水位差和重力作用影响;沙质河岸中的河水入渗前锋线呈凹凸形态,侧向潜流运动存在底部优势流现象,岸滩不同深度处的横向潜流交换速率大小存在差异;在单次河道水位涨落过程中,岸滩剖面内最大河水入渗面积出现在河道水位下降至略高于地下水位时。研究成果可为监测场地布置及河流生态保护提供参考。