Control of Water and Solute Movement in Soil using Geo-Textile

用埋地土工织物研究了在浅水位蒸发作用下控制溶质向上迁移的潜力。首先，利用土壤柱测量蒸发过程中水分和溶质分布。根据这些数据，计算了土工织物的土壤水通量和溶质通量。当周围土体吸力增加到20cm时，土工织物的非饱和电导率迅速下降到土的1/1000左右。溶质通量与水通量成正比，并受对流控制。因此，液态水运动是控制溶质向土壤表面转移的重要因素。然后，利用柱状试验获得的土工织物和土体的特性，进行数值模拟。在浅层地下水位蒸发的现场条件下，土壤水通量通常近似为时间和深度两个函数的乘积。土工织物埋置时，地下水状况对水通量分布模式有明显影响。通过推导合适的分布函数，得到了近似解。利用近似解和数值模拟结果表明，土工织物埋深、厚度和埋深特性对土壤水分通量和溶质迁移有较大影响。

A buried geo-textile was used to investigate the potential to control the upward migration of solutes under cvaporation from a shallow water table.First, experiments about water and solute distribution measuremants during evaporation using soil columns were conducted. From the data, soil water flux and solute flux through the geo-textile were calculated. The unsaturated conductivity of geo-textile decreased rapidly to about 1/1000 as that of the soil when the surrounding soil suction increasd to only 20cm. Also, the solute flux was proportionate to water flux and was controlled by convection. So, liquid water movement was concluded to be important in controlling solute tansfer to the soil surface.Next, using the characteristics of the soil and the geo-textile obtained in the column experiments, numerical simulation was carried out. Under field conditions of cvaporation from a shallow water table, soil water flux was usually approximated by the product of two functions of time and depth. When geo-textile was buried, the ground water condition makedly afffected the patters of water flux distribution. Deriving the proper distribution functions, an approximate solution was obtained. Using this approximate solution and the numerical simulation, the depth, the thickness, and the characteristics of geo-textile buried considerably affected the soil water flux and solute tranfer.