关键词: 腾发封顶, 毛细阻滞, 湿润地区, 土柱试验, 工作性能

Abstract: Capillary barrier evapotranspiration covers have many advantages over conventional covers. But they are mainly used in arid or semi-arid areas in USA and Europe. Whether they can be used in humid areas remains to be determined. Using low plastic silty clay and gravelly sand as material, a soil column is constructed in outdoor environment in Hangzhou and vegetation is planted. Water content, percolation and surface runoff are measured. Peak rainfall season, sunny and hot season, typhoon period and winter season are experienced during the monitoring 15 months. Results show that volumetric water content of silty clay changes greatly under natural infiltration and evapotranspiration; the and small dry-wet cycles exist in gravelly sand. It is shown that evapotranspiration acts on the whole depth of the cover. There comes percolation when silty clay in the bottom becomes saturated and volumetric water content of gravelly sand approaches 4%. The cover becomes temporarily ineffective and will soon be effective again when water content decreases due to vapor movement. Rainfall, surface runoff and percolation are 1 782.6, 53.08, 19.64 mm respectively. Most rainfall are stored in soils and later returned to the atmosphere by evapotranspiration. The cover can prevent percolation effectively during the test period.

Key words: evapotranspiration cover, capillary barrier, humid area, soil column test, working performance