Study On Soil Hydrological Characteristics Of Large Depth In North China Plain

It is not only the basis of deep understanding of the soil hydrology process to carry out the study on the hydrological characteristics of the large buried deep soil in the North China Plain,at the same time,it has a deep theoretical and practical basis for the improvement of hydrological research and regional ecological protection and management,it also provides scientific basis for research on groundwater recharge and excretion mechanism and regulation mechanism in large-depth burial depth in North China Plain.This article selects Kangzhuang Town of Yanqing County as the northwestern experimental area of North China Plain,Mulin Town of Shunyi District as the northeastern experimental area of North China Plain,and Yongledian Town of Tongzhou as the southeastern experimental area of North China Plain.Conduct field investigations in the test area to determine suitable sampling points,obtain spatial position information of each sampling point,soil profiles,and undisturbed soil samples required for the test.According to the difficulty of sampling in the field,the equivalent sampling mechanism of large-buried soil was proposed and its feasibility was verified;The soil hydrological parameters of the sample were measured indoors,and the statistical properties,correlations,and spatial distribution patterns of soil physical properties and soil hydrodynamic parameters under different buried depth conditions were analyzed in detail;The relationship between soil bulk density and saturated water content,permeability coefficient and saturated hydraulic conductivity was studied in detail.After detailed analysis of the above-mentioned research contents,the analysis conclusions are summarized as the following points.(1)Under the condition of the same texture,the soil vertical additional stress characteristics are used to calculate the sampling points of the vertical stress equivalent in different soil layers.By analyzing the soil hydrological parameters of the sampling points and the equivalent sampling points,it is found that the change range of bulk density and saturated water content is relatively small,and the permeability coefficient and soil moisture characteristic curve of the sampling point and the equivalent sampling point are highly correlated.It shows that the method of equivalent sampling is feasible in the field sampling.(2)Based on the traditional statistics and geostatistics methods,the statistical characteristics,variation trend,correlation and spatial distribution of soil hydrological parameters under different buried depth conditions are analyzed in detail.The results show that the soil texture shows a distinct level with the depth of the buried depth.For example,the soil texture in Yanqing test area belongs to the interlayer type model(soil clip adhesion);the soil texture of Tongzhou test area belongs to the homogeneous model(the common body soil);the soil texture in Shunyi test area belongs to the light model under the upper weight(loam cap sand).The soil texture shows a distinct level with the depth of the buried depth make the soil bulk density have a certain spatial variation rule.Among them,the bulk density of each soil section in Yanqing,Tongzhou and Shunyi test area decreased first and then increased with the increase of soil depth;The response relationship between the saturated water content and the bulk density is negative correlation and obviously significant;Under the condition of soil depth change,the change trend of saturated water content and the trend of bulk density are opposite to the change trend of buried depth.In addition,between the 0-1m of the soil surface is influenced by human activities,the surface soil is more dense and the permeability coefficient is smaller;Depth of soil between 1-3m,the soil permeability coefficient is the largest,and then the permeability coefficient decreases with the increase of buried depth.(3)Soil permeability coefficient varies significantly with the depth of buried depth.With the increase of soil depth,the soil permeability coefficient increased first and then decreased gradually.It also decreased with the increase of soil bulk density.The soil permeability coefficient is also concentrated when the amplitude of bulk density changes is small.(4)From the soil moisture characteristic curve of the large buried deep soil in the Yanqing experimental area,the soil water suction gradually decreased with the increase of soil water content.Under the same soil suction condition,the soil moisture content of loam clay is larger than that of silty sandy loam.Under the same soil suction condition,the water content of sandy clay loam is larger than that in clay loam.The soil saturated water conductivity fluctuates frequently,and there is no obvious change with the increase of buried depth.But the saturated water conductivity of the surface soil is obviously larger than that of the other buried deep water,the main reason is that human farming has enhanced the permeability of surface soil moisture.In addition,in the Shunyi Experimental Area,in addition to the large value of the saturated hydraulic conductivity of the surface soil,the soil saturated hydraulic conductivity value at the depth of 1.5m is also large.This is due to the change in soil texture from silty loam to sandy soil.