| In karst areas,a large amount of soil erosion has caused serious rocky desertification on slopes.The soil and rocks of rocky desertification slopes are inlaid and distributed.From the perspective of its distribution characteristics,it can be divided into three typical soil and rock structure types:(1)The surface soil layer is continuous,but the soil layer is thin,and the rock has not been exposed to the surface,which is referred to as FE(rock fully embedded in the soil layer);(2)The surface soil layer is discontinuous,and part of the bedrock is exposed to the surface,which is referred to as PE(rock partly embedded in the soil layer);(3)The rock is covered on the surface,which is referred to as RC(rock covering the surface).The above-mentioned soil and rock structure can affect the hydrological process and soil erosion process on the slope.In order to further understand the hydrological processes and soil erosion characteristics of karst slopes with different soil and rock structures,this paper adopts artificial rainfall simulation experiment method,the different soil and rock structures on karst slopes as the research object.The runoff characteristics of surface runoff,interflow and underground runoff and soil erosion characteristics under different rainfall intensities,slopes,rock and soil ratios and successive rainfalls conditions were studied.The research results can provide an important theoretical basis for the control of rocky desertification on karst slopes.The main research results are as follows:(1)Rainfall intensity,slope,rock-soil ratio,and successive rainfalls have different effects on the initial runoff time of surface runoff,interflow and underground runoff on slopes with different soil and rock structures.Especially under the conditions of high rainfall intensity and steep slope,the initial runoff time of surface runoff and interflow of soil and rock structures slopes was advanced.At the same time,the increase in the rock-soil ratio also shortened the initial runoff time of surface runoff and interflow on slopes,while the initial runoff time of underground runoff responds differently to the above influencing factors.In addition,the number of rainfall events will also affect the initial runoff time of the sloping land surface,that is,the initial runoff time of each runoff significantly advances with the increase of rainfall events.(2)The runoff rate of the three types of soil and rock structure slopes showed different variation rules due to the different rainfall intensities,slopes,rock-soil ratios and successive rainfalls.The surface runoff rate of FE,PE and RC increased with the increase of rainfall intensity,slope,rocksoil ratio and successive rainfall events,and the surface runoff rate generally showed a trend of slow growth-stable or slow growth-fluctuation.The interflow rate decreased with the increase of rainfall intensities,rock and soil ratios and successive rainfall events,and increased with the increase of slopes.Overall,the underground runoff rate varies with rainfall intensity,slope,rock and soil ratio and successive rainfall events increased and decreased,and both the interflow rate and the underground runoff rate showed a trend of first increasing and then decreasing with the extension of runoff time.(3)When the rainfall intensity was 50 mm/h and the rock-soil ratio was 12%,the surface runoff of the FE and PE was smaller than that of the RC,indicating that the rock embedded in the soil has the effect of reducing surface runoff.In addition,whether it was a gentle slope or a steep slope,the total FE and PE both reduced the surface runoff compared with the RC.However,when the rainfall intensity was 75 mm/h,the effect of rock embedded in the soil on surface runoff had two sides,which may reduce the surface runoff yield and increase the surface runoff yield;when the rock-soil ratio was 24%,the FE and PE increased the surface runoff yield by more than 64%;The runoff yield increased with the increase of rainfall events.In addition,the interflow of different soil and rock structure slopes decreased with the increase of rainfall intensity and rock-soil ratio,but increased with the increase of slope and successive rainfall events.The effects of rainfall intensity,slope,rock-soil ratio and successive rainfalls on the underground runoff vary greatly,among which,the underground runoff decreased with the increase of slope and rock-soil ratio.(4)Compared with RC,under the conditions of rainfall intensity of 50 mm/h and rock-soil ratio of 12%,FE and PE reduced the amount of surface yield;when the rainfall intensity was 75 mm/h and the rock-soil ratio was 24 %,the FE and PE increased the surface sediment yield.In addition,regardless of whether it was gentle slope or steep slope,compared with the RC,the FE and PE both reduced the surface sediment yield.The surface sediment yield of slopes with different soil and rock structure increased with the increase of successive rainfalls. |
