Experimental Study On The Influence Of Rock And Soil Configuration On Hydrological Connectivity And Erosion And Sand Production In Southwest Karst Slope

Karst area fragile ecological environment,shallow soil,serious soil erosion leads to rock exposure,rocky desertification problem is very prominent,plus in recent years southwest karst frequent extreme rainfall,the soil erosion is increasingly serious,and the ground,underground binary sand erosion may be mainly controlled in slope hydrological connectivity.To this end,this study designed different undulating bedrock height(undulating bedrock,flat bedrock)and rock cover pattern(blank pattern,point pattern,patch pattern,lateral pattern,cross pattern;the rock coverage rate was all set at 30%),conduct a simulated rainfall test,using non-parametric test and generalized linear model(GLM)methods,analyze the influence mechanism of different rock and soil structures on slope sand production,and reveal the mechanism of erosion on slope hydrological connectivity of extreme rainfall background in karst rocky desertification area.The main results are as follows:(1)For flat bedrock slopes,the surface runoff flow is cross pattern> lateral pattern>patch pattern> point pattern> blank pattern,the runoff production and flow at rock and soil interface is blank pattern> point pattern> lateral pattern> cross pattern> patch pattern,underground runoff flow is blank pattern> point pattern> patch pattern> lateral pattern> cross pattern;for the undulating bedrock slope surface,the surface runoff flow is cross pattern>lateral pattern> patch pattern> point pattern> blank pattern,the runoff production and flow at rock and soil interface is blank pattern> point pattern> lateral pattern> cross pattern> patch pattern,the flow of underground runoff is blank pattern> point pattern> patch pattern> lateral pattern> cross pattern.(2)Rock and soil structure has a significant impact on the surface runoff,rock and soil interface flow,and underground runoff.The influence of the generalized linear model(GLM)on rock cover pattern and underground bedrock fluctuation on runoff shows that,under the same rain-intensity conditions,the contribution rate of surface rock cover pattern to surface runoff accounts for 92.1%,which is the main factor affecting slope surface runoff.The contribution rate of bedrock fluctuation to geotechnical interface runoff and underground runoff accounts for 60.4% and 88.8% respectively,which are the main factors affecting geotechnical interface runoff and underground runoff.The surface production flow of five rock cover patterns is: cross pattern> lateral pattern> patch pattern> point pattern> blank pattern;while the rock and soil interface and underground production flow are: undulating bedrock> flat bedrock.(3)For the flat bedrock slope,the surface sediment yield is cross pattern> lateral pattern> patch pattern> point pattern> blank pattern.For the undulating bedrock slope surface,the surface sediment yield is the cross pattern> lateral pattern> patch pattern> point pattern>blank pattern.(4)Under the same rain strength conditions,the surface total sediment yield of different rock cover patterns is significantly different,and the rock cover pattern has a significant impact on the slope sediment yield,the surface totle sand production of the five rock covering patterns were all cross pattern> point pattern> patch pattern> lateral pattern> blank pattern.Except for the blank pattern,there is no sand production at the rock and soil interface and under the other four patterns.The reason for the unproduced sand may be the pipeline blockage and the sediment particles can not leak.By comparing the rock and soil interface and the underground sediment production,it can be seen that the bedrock fluctuation is an important factor affecting the rock and soil interface and the underground sediment production.(5)The structural hydroconnectivity of different rock cover patterns was calculated according to the directional permeability index,with the structural connectivity of blank pattern 0,point pattern 0.437,patch pattern 0.553,lateral pattern 0.645,and crossover pattern0.767.Calculate the functional hydrological connectivity of different rock cover patterns based on the relative surface connection function,Functional connectivity ranged between 0 and 0.2,cross pattern functional connectivity between 0.75～1,lateral patterns between 0.6～0.8,point patterns between 0～0.5,and patch patterns between 0～0.5.The slope sand and abortion yield is closely related to hydrological connectivity,the slope flow production and hydrological structure connectivity have good correlation,and the flat bedrock hydrological structure connectivity has significant positive correlation with sediment;the slope sediment yield shows significant correlation with functional hydrological connectivity,the stronger the functional hydrological connectivity,the more sediment yield,so the functional hydrological connectivity may better represent the influence of hydrological connectivity on eroded sand production than the structural hydrological connectivity.