The Soil Mechanics Mechanism Of Soil Erosion Process In Karst Slope Cropland In Central Guizhou Province

Soil mechanics index(especially soil internal friction angle,cohesion and compactness)are important reference and calculation parameters in soil erosion control engineering design.Based on the principle of soil erosion,the soil mechanics mechanism of soil erosion process in karst slope cropland in central Guizhou province was studied by field investigation and indoor experiment and experiment.The results show that there is a close relationship between soil mechanical properties and soil basic attribute index.The main conclusions are as follows:(1)Soil mechanical characteristics in karst slope cropland in central Guizhou province.There were significant differences in soil internal friction angle,cohesion and compactness between tillage layer and non-tillage layer.The internal friction angle of the tillage layer is 0.985°lower than the non-tillage layer,the cohesion of the tillage layer is 0.015 kPa lower than the non-tillage layer,and the soil compaction degree of the tillage layer is 189 kPa lower than the non-tillage layer.There were significant differences in soil internal friction angle and cohesion between limestone and dolomite,the internal friction angle in the limestone area is 1.355°higher than the dolomite area,and the cohesion in the limestone area is 1.515 kPa lower than the dolomite area,soil compactness was not significant difference,compaction: Dolomite area(1400kPa)>limestone region area(1134kPa),non-tillage layer(1424kPa)> tillage layer(1221kPa).(2)The relationship between soil basic properties and soil mechanical properties.The soil internal friction angle increases with the increase of bulk density,and the cohesion increases first and then decreases with the increase of bulk density,and the soil compactness increases logarithmically with the increase of bulk density in limestone area.The soil internal friction angle increases with the increase of bulk density,and the cohesion increases first and then increases with the increase of bulk density in dolomite area.The soil compactness increases with the increase of bulk density.The internal friction angle of the sloping land of limestone is decreased with theincrease of natural water content,and the cohesion increases with the increase of natural water content in limestone area.The internal friction angle of the soil in the dolomite sloping land decreased with the increase of the natural water content,and the cohesion increased with the increase of the natural water content.Soil compactness has no obvious change with natural water content in dolomite area.The internal friction angle of the sloping land of the limestone is decreased with the increase of soil organic matter,and the cohesion increases with the increase of soil organic matter in limestone area.The internal friction angle of soil in the dolomite sloping land decreased with the increase of soil organic matter,and the cohesion increased with the increase of soil organic matter.Soil compactness had no obvious change with the increase of soil organic matter,but the positive correlation was positive in dolomite area.The internal friction angle increases with the plasticity index increasing,and the cohesion increases first and then increases with the plasticity index increasing in limestone area.The soil internal friction angle increases with the plasticity index increasing,and the cohesion increases with the plasticity index in dolomite area.In general,the difference of plasticity index between cultivated layer and non-tillage layer was significant,and the difference of plasticity index was not significant,there were significant differences in the liquid index between limestone and dolomite,plasticity index difference is not significant.(3)The relationship between soil fractal dimension and soil mechanics properties.There is a positive correlation between soil internal friction angle and fractal dimension.The soil cohesion of dolomite area increased first and then decreased with the increase of fractal dimension in dolomite area.There were significant differences in soil mechanical composition and fractal dimension between the same soil parent soils,the fractal dimension is negatively correlated with the percentage of soil coarse sand mass,and the fractal dimension is positively correlated with the percentage of fine sand,powder and clay mass in tillage layer of limestone area,the fractal dimension is negatively correlated with the percentage of coarse sand mass,but the correlation is not obvious.The fractal dimension is positively correlated with the percentage of fine sand,powder and clay mass in non-tillage layer of limestone area.There was a negative correlation between the fractal dimension and the percentage of coarse sand content,and the fractal dimension was positively correlated with the percentage of fine sand,powder and clay mass intillage layer of dolomite area,the fractal dimension is negatively correlated with the percentage of coarse sand and fine sand mass,and the fractal dimension is positively correlated with the percentage of grain and clay mass in non-tillage layer of dolomite area.(4)The mechanism analysis of soil erosion based on soil mechanical properties.The tillage process makes the soil fine,there was a significant difference in the liquid index between the tillage and non-tillage layers,The plasticity index(6.69%)of the tillage layer was higher than that of the non-tillage layer(6.58%),and the liquidity index(0.743)of the tillage layer was higher than that of the non-tillage layer(0.608).There are significant differences in the liquidity index between limestone and dolomite.There are not significant differences in the plasticity index between limestone and dolomite.After the cultivation of soil erosion resistance,but its erosion resistance is weakened.Soil fine particle content dolomite soil is more than limestone,soil anti-dispersal scouring ability limestone is stronger than dolomite,from the perspective of soil mechanics,the sloping land in the limestone area is more stable than that in the dolomite area.The study shows that the tillage process accelerates the soil erosion,and the limestone soil is not easy to be lost than the dolomite in karst slope cropland in central Guizhou province.