Study On Soil Infiltration Of Purple Sandstone

In this paper,the purple sandstone development soil in the Wangjiaqiao small watershed of the Three Gorges Reservoir area is taken as the research object.The physical and chemical properties of the soil are obtained through experiments,and the basic properties of the three types of land use(orchard,forest land,cultivated land)are analyzed;The characteristics of the developed soil pores and the distribution of macropores are studied.At the same time,the effects of soils with different development levels on the hydraulic properties of the soil were studied in combination with the water characteristic curve.Finally,the water infiltration parameters were obtained through the disk infiltration test,and the basic physical and chemical properties and macroporosity distribution measured above were used to analyze the soils with different development degrees Law of water infiltration.The following results were obtained:(1)Three types of land use were selected on the soil developed with purple sandstone,and the differences in physical and chemical properties between different development levels of the soil were analyzed.The results show that in the three types of land use,the average soil bulk density is forest land>orchard>cultivated land;the average soil clay content is cultivated land>orchard>forested land;the soil gravel content is forested land>orchard>cultivated land;the soil organic matter content is orchard>cultivated land >Woodland.The indicators of different soil levels also have very significant differences,and the physical and chemical properties of different soil levels vary greatly;(2)The main factors affecting the soil hydraulic characteristics are bulk density,clay content,organic matter content,and gravel content.Among them,soil bulk density has the greatest influence on the water characteristic curve,and the gravel content is the smallest.For the three soils of the same parent material,the difference in water characteristic curve is not obvious at the low suction stage.The purple normal newly formed soil and the purple wet prototype soil change more than the acidic wet leaching soil in the high suction section,and the change ranges are purple normal new Formed soil>Purified moist prototype soil>Acid moist leached soil,indicating that the aerated pore content of purple normal newly formed soil and purple moist prototype soil is much higher than that of acid moist leached soil,and the acid moist leached soil mainly consists of capillary pores and invalid pores Mainly;(3)There are also significant differences in the distribution of soil pores in the three profile configurations.The large porosity of the soil is purple normal new soil>purple humid prototype soil>acid humid leaching soil.At the same time,during the process of soil macropores decreasing with the degree of soil development,the content of smaller pores in the soil gradually increases,the overall connectivity of the soil decreases,and the pore length density also decreases.The smaller the pores,the higher the sphericity of the pores.The larger the wet circumference of the cross-section,the smaller the hydraulic radius;(4)The higher the degree of soil development,the lower the soil permeability.The same soil with the soil depth increases,the soil permeability decreases layer by layer.The basic physical and chemical properties of the soil have a significant effect on water infiltration,and the large pores of the soil also have a large effect on the soil infiltration performance.During the development of the soil,the change of soil physical and chemical properties and the difference in the distribution of pores led to the difference in soil infiltration.The infiltration performance was purple normal newly formed soil>purple wet prototype soil>acid wet leaching soil.As the soil develops higher,the soil permeability decreases,and the same soil with the soil depth increases,the soil permeability decreases layer by layer.According to the above results,when the degree of soil development is determined,the law of water infiltration in the soil can be determined to a greater extent,which has a greater theoretical guiding role in the prevention and control of soil erosion and rational land use in areas with complex soil development environments.