Studies On Soil Antierodibility Assessment Factors Of Different Soil Horizons Of Collapse Gullies In Granite Region Of Southern China

In the southern granite area of china, collapse gullies'erosion is very serious. Typical collapse gullies were selected in Longmen, Anxi County. We studied the soil anti-erodibility assessment factors on different soil horizons of collapse gullies. Originally, 17 factors were selected to analyse, including the physical indicators, chemical indicators, mechanical indicators and aggregative indicators.After weeding out the indicators ,whose variation coefficient was less than 10%, organic matter content, ba value, clay ratio, micro-aggregate content, degree of aggregation, structure coefficient, initial permeability rate, stable permeability rate, shear strength and erosion rate of 10 representative indicators were left. Using cluster analysis to classify these indicators, different types of the anti-erosion index scores were calculated though fuzzy synthetical evaluation method. In order to verify the reliability of cluster analysis, we proceeded to evaluate the overall indicators. Finally, we got the comprehensive evaluation result of different horizons'anti-erodibility and the best indicators to attribute the soil anti-erodibility.The indicators were classified into three clusters using cluster analysis.Cluster 1(texture and permeability cluster): organic matter content, ba value, clay ratio, initial permeability rate, stable permeability rate;Cluster 2(aggregate and structure cluster): micro-aggregate content, degree of aggregation, structure coefficient, erosion rate;Cluster 3(mechanical property cluster): shear strength.The three clusters were evaluated though fuzzy synthetical evaluation method separately. The comprehensive evaluation scores of the three horizons showed that descending order of anti-erodibility was red soil horizon, sandy soil horizon and detritus horizon. That was accorded with the evaluate result which was calculated using the overall indicators.Therefore,the conclusion is that descending order of anti-erodibility in collapse gullies is red soil horizon, sandy soil horizon and detritus horizon. The best indicators to attribute the soil anti-erodibility are erosion rate, clay ratio and stable permeability rate. The absolute values of the correlation coefficient between the each two indicators are greater than 0.7 entirely. It is in accordance with the standard that if r≥0.7,then the two indicators are all considered as the dominant factors. So erosion rate, clay ratio and stable permeability rate are the dominant factors of antierodibility of different soil horizons of collapse gullies in southern China.