黄土区沟道阶梯状边坡水土流失防治措施与机理

陕北地区治沟造地工程中新修沟道阶梯状边坡抗蚀性较弱。研究利用室内人工模拟降雨试验,研究新开挖沟道阶梯状边坡在降雨作用下不同水土保持措施的水沙效应,并观测其侵蚀发育过程。结果表明:极端气象条件(120mm/h雨强)与坡顶部区域汇水作用是导致阶梯状边坡产生快速侵蚀破坏的两个主要条件。当边坡仅受到降雨作用,雨强在60mm/h~90mm/h之间变化时,产沙速率稳定,不同雨强下产沙速率呈现倍率关系,坡面侵蚀现象无明显差异,坡体无明显破坏;120mm/h雨强条件下,产沙速率显著上升,侵蚀发育过程出现明显变化,坡体破坏明显。阶梯状边坡平台反坡措施能有效减少60mm/h,90mm/h,120mm/h三种雨强下产沙量58.4%,35.2%,62.1%,减少径流量69.6%,26.6%,60.8%,并有效减缓坡体表面破坏及侵蚀发育速度。用放水试验模拟无截排水措施情况,发现截排水措施能够有效降低产沙量92.7%,同时改变了侵蚀发育的现象,将急剧下切发育的细沟侵蚀转变为了发育较为缓慢的层状面蚀。从减水减沙的角度,坡顶截排水措施与平台反坡措施皆为有效的阶梯状边坡水土流失防治措施。

Measures and Mechanism to Prevent Water Loss and Soil Erosion on Multi-Stair Slope in Loess Area

The new built multi-stair slope in gully of loess area is susceptible to soil erosion.We used the simulated rainfall experiment to examine the relation among soil and water conservation measures,rainfall intensity and the phenomenon of soil erosion on multi-stair slope in loess area and observed the development process of soil erosion.The results show that the extreme weather conditions (rainfall intensity 120 mm/h) and upslope runoff are two key factors leading to soil erosion on multi-stairs slope in loess area.When the rainfall intensities ranged between 60 mm/h～90 mm/h,the sediment yield rate influenced by the rainfall was stable.There was no obvious difference between phenomena of soil erosion and the slope without obvious damage,When the rainfall intensity was 120 mm/h the sediment yield rate rose quickly,the phenomenon of soil erosion was obvious.The reverse slope measure can effectively reduce the sediment yield by 58.4％,35.2％,62.1％ and reduce the runoff by 69.6％,26.6％,60.8％,respectively,under the rainfall intensities of 60 mm/h,90 mm/h and 120 mm/h.At the same time,the erosion rate decreased.Water test was used to simulate the slope without drain measures.The results show that drain measures can effectively reduce the sediment yield by 92.7％,and at the same time changed the development phenomenon of erosion,the drain measure turned the erosion phenomenon from rill erosion to sheet erosion.From the point of view of water and sediment reduction,the drain measures and reverse slope measures are both effective measures to prevent water loss and soil erosion on multi-stair slope in loess area.