层状土中毛管水上升的实验研究

土壤盐渍化的重要机制是地下水中可溶盐在蒸发作用下不断向表土聚集;次生盐渍土的形成则可能是由于人为抬高地下水位,土壤毛管水重新分配土中盐分所致.不管怎样,防止土壤盐渍化的积极而彻底的方法是消除地下水位抬高的因素.但是,全面而根本的措施,往往限于客观条件不易做到,因此大多数都采取治标措施.例如,利用耕耘增加毛管水上升的困难,以及洪淤压碱等等.

EXPERIMENTAL INVESTIGATION OF UPWARD MOVEMENT OF SOIL WATER IN LAYERED SYSTEMS

A laboratory investigation was conducted for capillary water rise in,and evaporation from two and three layered soil columns in the presence of a water table.It was shown from experimental results that the evaporation rate from the two layered system of clayey soil overlying a sandy soil was a maxium,as the layered soil interface was situated near the top of capillary fringe of the lower soil;but that the rate from the three layered system of a thin clayey layer laid between two sandy soil layers was a minimum,as the thin clayey layer was situated at a elevation,approximately equal to the height of capillary fringe of the lower sandy soil layer;and that the effect of the lower sandy soil,the thickness of which is not beyond its capillary fringe zone,of the two layered system on the evaporation rate was relatively small,provided the depth of soil column to the water table was less than the height of capillary fringe of the upper clayey soil.Evidently,all of these phenomena observed must be considered for adequately determining the depth of ground water table to avoid soil salinity.