崩岗不同土层土壤水力学特性差异性分析

Analysis on the Difference of Soil Hydraulic Properties in Different Soil Layers of Benggang

为研究崩岗不同土层土壤水力学特性的差异性,采用离心法测定不同土层土壤水分特征曲线,筛选出适合的土壤水分特征曲线拟合模型,结合统计模型,推求土壤的当量孔径分布、比水容量、非饱和导水率和扩散率,分析崩岗不同土层土壤水力学参数的变化规律。结果表明,崩岗土层从红土层到砂土层的变化过程中,土壤质地由黏土向砂土变化;Fredlund&Xing模型对崩岗土壤土水特征曲线拟合效果最好;参数θs、α、n随着质地变黏重逐渐减小;随着土层深度的增加,土壤的持水性能降低;土壤比水容量、非饱和导水率和扩散率受土壤质地和基质吸力的共同影响。在低吸力阶段,3个指标随基质吸力变化比较平缓,砂土层土壤比水容量和非饱和导水率最大,扩散率最小;而在高吸力阶段,砂土层土壤的这些指标降低较快,且低于其他土层,各层土壤间导水率和扩散率差异随着基质吸力的增加而增大。

In order to study the difference in hydraulic characteristics of different soil layers in benggang,soil-water characteristic curves of different layer soils were measured by using the high-speed centrifuge method,and a suitable soil-water characteristic curve(SWCC)fitting model was screened.Soil equivalent pore size distribution,soil specific water capacity C(θ),unsaturated conductivity K(θ),and soil water diffusivity D(θ)were calculated and then analyzed based on the selected SWCC model and soil hydraulic statistical models.Results showed that soils shifted from clay to sand gradually with soil depth increased.Among the frequently-used SWCC models,the Fredlund&Xing model was the optimal one for benggang.The model fitting parametersθs,α,and n decreased when soil texture changed from sand to clay.As the depth of the soil layer increased,the water holding capacity of the soil decreased.The values of C(θ),K(θ),and D(θ)were influenced by both soil texture and water content(or suction).In the low suction stage,these three indices changed gently with soil suction,and the values of C(θ)and K(θ)of sandy layer soils were larger than those in other layers;while the performance of D(θ)was the opposite,which were mainly controlled by macropores.In the high suction stage,all those indices of sandy layer soils decreased rapidly and were lower than other layers;the difference of K(θ)and D(θ)values between different layer soils become bigger and bigger with the suction increased,which was due to the clay adsorption and soil capillarity of micropores.