Study On Water Infiltration Characteristics And Applicable Model Of Pisha Sandstone Soil

The Pisha Sandstone is distributed in the Yellow River basin centered on the bordering area of Shanxi,Shaanxi and Inner Mongolia.The ecological environment in this area is seriously deteriorating,and it is the region with the most serious soil erosion in China.In the process of conversion between groundwater and precipitation,soil water,and surface water,soil infiltration is a very important part,so only by in-depth analysis of the infiltration characteristics of Pisha Sandstone soil,it is possible to grasp the soil erosion law in this area.It is of great significance for Pisha Sandstone water and soil conservation work and ecological vegetation restoration construction.This paper analyzes the infiltration characteristics of Pisha Sandstone by using a combination of indoor soil column infiltration test and field observation on the constructed homogeneous Pisha Sandstone and undisturbed Pisha Sandstone.Through analysis of multiple relatively mature soil moisture infiltration models in foreign countries to test the applicability to Pisha Sandstone,the optimal model was selected,and the soil moisture distribution and the change of moisture content after rainfall in the field of complete Pisha Sandstone slope were observed and analyzed.conclusion as below:(1)With the increase of the initial water content,the infiltration rate and cumulative infiltration volume of homogeneous Pisha Sandstone decrease,but the migration speed of the moist front increases,and the lower the initial water content,the drier the soil,the greater the infiltration depth in the same time The shallower,the longer it takes to reach saturation.The infiltration capacity of homogeneous Pisha Sandstone decreases with the increase of bulk density,and the infiltration rate,cumulative infiltration volume and wetting front transport rate all have a negative correlation with soil bulk density,which shows that the high bulk density of Pisha Sandstone will affect the pore volume of Pisha Sandstone The ability of structure,water conductivity and other aspects,which in turn affect the movement of water.(2)The infiltration experience time of undisturbed Pisha Sandstone is longer than that of homogeneous Pisha Sandstone,and the time to reach stable infiltration is more than 3 hours.The average values of initial infiltration rate and stable infiltration rate are 0.677cm/min and 0.008cm/min,both of which are significantly smaller than the corresponding values of the homogeneous Pisha Sandstone with design bulk density and water content.This indicates that the pore structure of homogeneous Pisha Sandstone after the disturbance has changed,and the infiltration capacity is much greater than that of the original Pisha Sandstone.(3)Both the Kostiakov model and the Philip model are suitable for simulating the curve of the infiltration rate of homogeneous Pisha Sandstone with time.In the one-dimensional vertical infiltration test,the determination coefficient R2 of the Kostiakov model is greater than 0.99,and the best fitting effect.In the one-dimensional horizontal infiltration test,the fitting accuracy of the Philip infiltration model is the highest.Using the Kostiakov model,Philip model and Horton model to test the applicability of undisturbed Pisha Sandstone,the results show that the correlation coefficients R2 of the three models are all above 0.90,and the Kostiakov model has the highest correlation coefficient of the fitted curve.(4)The soil moisture on the complete slope of Pisha Sandstone showed a gradual increasing trend with the increase of the depth of the soil layer,but due to the alternating distribution of Pisha Sandstone with different properties,the storage water and permeability of each layer are different,resulting in uneven soil moisture distribution The water content of mudstone is significantly greater than that of pink sandstone and off-white sandstone.After rainfall,the soil water content on the slope surface generally showed an increasing trend,but the deep Pisha Sandstone had a smaller increase than the surface Pisha Sandstone.