坡度影响下的砒砂岩区裸露坡面水分入渗特征及模拟

为探究不同坡度(5°,10°,20°,30°)条件下,不同质地砒砂岩土壤(灰白色、混合色、紫红色)的水分入渗特征及最优入渗模型。通过室内模拟土柱法对土壤的水分入渗特征和拟合结果进行对比分析。结果表明:(1)研究区不同坡面土壤容重在1.513~1.737 g/cm³,30°坡面下的灰白色砒砂岩土壤入渗能力较强,5°坡面下的紫红色砒砂岩土壤入渗能力较弱。(2) 在砒砂岩土壤一维垂直 入渗过程中,初始入渗率为2.000~8.600 cm/min,入渗时间3.500~5.000 min后达到稳定入渗率(0.160~1.800 cm/min)。入渗率、湿润锋运移速率与时间呈幂函数递减关系。坡度的大小、砒砂岩的质地均影响砒砂岩土壤入渗能力,坡度越小、颜色越深, 入渗率、累计入渗率越低,湿润锋运移越慢;且初始入渗速率、稳定入渗速率、初始湿润锋运移速率、稳定湿润锋运移速率的值均随着坡面坡度的减小、砒砂岩土壤颜色的加深呈现减小趋势。(3)Kostiakov模型、Philip模型对于砒砂岩区土壤水分入渗结果拟合较好,决定系数均在0.900以上。Kostiakov模型 决定系数的平均值0.948拟合效果最优;Philip模型决定系数的平均值0.937拟合效果其次;Horton模型决定系数的平均值0.688拟合效果较差。通过平均绝对误差(MAE)、均方根误差(RMSE)、偏差百分比(PBIAS)、纳什效率系数(NSE)验证Kostiakov模型和Philip模型模拟值与实测值的差异性小、两者吻合程度高。

Water Infiltration Characteristics and Simulation on Exposed Slope in Pisha Rock Area Under the Influence of Slope

In order to explore the water infiltration characteristics and optimal infiltration model of arsenic sandstone soil (gray white, mixed color, purplish red) with different textures under different slopes (5°, 10°, 20°, 30°), the characteristics of soil water infiltration and fitting results were compared and analyzed by indoor simulated soil column method. The results showed that:(1) The soil bulk density of different slopes in the study area is 1.513~1.737 g/cm³. The soil infiltration capacity of gray white arsenic sandstone under 30° slope was strong, and the soil infiltration capacity of purple red arsenic sandstone under 5° slope was weak. (2) In the process of one-dimensional vertical infiltration of arsenic sandstone soil, the initial infiltration rate was 2.000~8.600 cm/min, and the stable infiltration rate (0.160~1.800 cm/min) was reached after the infiltration time was 3.500~5.000 min. The infiltration rate and wetting front migration rate decreased with time in a power function. The smaller the slope and the darker the color was, the lower the infiltration rate and cumulative infiltration rate was, and the slower the migration of wetting front was. The values of initial infiltration rate, stable infiltration rate, initial wetting front migration rate, and stable wetting front rate all decreased with the decrease of slope gradient and the deepening of arsenic sandstone soil color. (3) Kostiakov model and Philip model fit well the results of soil water infiltration in arsenic sandstone area, and the determination coefficients were more than 0.900. The average value of the decision coefficient of Kostiakov model was 0.948, and the fitting effect was the best. The average value of Philip model determination coefficient was 0.937, and the fitting effect was the second. The average value of the determination coefficient of Horton model was 0.688, and the fitting effect was poor. Through the mean absolute error (MAE), root mean square error (RMSE), percentage of deviation (PBIAS), and Nash efficiency coefficient (NSE), it was verified that the simulated values of Kostiakov model and Philip model have little difference and high degree of coincidence with the measured values.