紫色土和红壤坡面径流分离速度与水动力学参数关系研究

Relationships between soil detachment rate and runoff hydrodynamic indexes of purple soil slope and red soil slope

土壤剥蚀是土壤侵蚀、搬运和沉积过程中的一个重要子过程,对其定量研究是建立具有明确物理意义侵蚀模型的理论基础。采用放水冲刷法,在3.0m长、1.0m宽的土槽上,通过4个不同坡度(5°、10°、15°、20°)、5个不同放水流量(1.3l/min、3.0l/min、5.5l/min、6.5l/min、8.5l/min)的组合实验,对红壤和紫色土坡面径流分离速度与径流剪切力、单位水流功率、水流功率、过水断面单位能量之间的关系进行了研究。结果表明:在一定的坡度条件下,分离速度随放水流量的增大而增大,而对于相同的放水流量,分离速度呈现出先增大后减小,然后趋于稳定的趋势,且有随放水流量的增大达到峰值的时间有提前趋势。径流剪切力、单位水流功率、过水断面单位能量及水流功率四个参数与分离速度均存在着明显的线性关系,但相对而言,水流功率更能准确反应坡面分离速度的变化情况。实验条件下,红壤坡面土壤剥蚀的临界水流功率值为0.0083N/(m.s),紫色土坡面土壤剥蚀的临界水流功率值为0.062N/(m.s)。

Soil detachment process is one of the very important processes of erosion,transportation and deposition.Quantitative study of the soil detachment process is the basis of building the significant physical implication of soil erosion and prediction model.Taken the red soil and purple soil slopes respectively as the research fields,which was 3.0 long and 1.0 wide,a series of scouring experiments at 4 slope gradients(5°、 10°、15°、20°) and 5 water discharges(1.3l /min、3.0l /min、5.5l /min、6.5l /min、8.5l /min) were conducted.The relationships between soil detachment rate and runoff shear stress,unit stream power,stream power and cross-section specific energy are studied in this paper.The results show that the soil detachment rate increased with the increase in water discharge at the same slope gradient.Soil detachment rate increased at the beginning and then decreased,at last,the soil detachment rate became stable at the same water discharge.The time of soil detachment rate reaching its peak value became shorter along with the increase in water discharge.There exited a good linear relationship between the soil detachment rate and runoff shear stress,unit stream power,stream power and cross-section specific energy.All of these four indexes could be used for reflecting the soil detachment rate,but the stream power was better than the others.For the red soil the critical shear stress was about 1.25N /m2 and for the purple soil it was about 2.16N /m2.For the red soil the critical unit stream power was about 0.00014m /s and for the purple soil it was about 0.0018m /s.For the red soil the critical stream power was about 0.0083N /(m.s) and for the purple soil it was about 0.062 N /(m.s).For the red soil the critical cross-section specific energy was about 0.24cm and for the purple soil it was about 0.23 cm.