紫色土丘陵区生物埂不同植被类型土壤分离水动力学特征

Hydraulic Characteristics of Soil Detachment Under the Terrace Banks with Different Vegetation Types in the Purple Hilly Area

野外采集紫色土区六棱型预制网格式护坡生物埂内不同植被类型原状土样,通过室内模拟细沟水槽(长4 m,宽0.12 m,深0.1 m)冲刷试验,探究不同植被类型影响下土壤分离能力与水动力学参数之间的关系。选择麦冬、韭菜2种生物埂类型,以单一网格式裸坡为对照,在3个坡度(15°,20°,25°)、5个流量(39.86,59.98,79.67,100.45,121.16 L/min)组合条件下进行冲刷试验。结果表明:生物埂内不同植被类型下土壤分离能力差异显著(P<0.05),表现为麦冬(均值2.24 kg/(s·m^2))>对照(均值1.34 kg/(s·m^2))>韭菜(均值1.09 kg/(s·m^2))。幂函数方程可用于描述土壤分离能力与水流剪切力(R^2=0.75)、水流功率(R^2=0.73)、单位水流功率(R^2=0.46)及过水断面单位能量(R^2=0.63)间的数学关系。生物埂各植被类型下土壤发生分离的临界剪切力τ_c表现为τ_c麦冬(8.75 Pa)>τ_c韭菜(6.47 Pa)>τ_c对照(1.93 Pa),表明植被可增强网格式护坡生物埂土壤抵抗分离的能力。

To determine the relationships between soil detachment capacities and hydrodynamic parameters under Terrace Banks in hexagonal prefabricated net format with different vegetation types, we collected the undisturbed soil samples in Terrace Banks planted with Ophiopogon japonicus, Allium tuberosum and bare land(control) in situ respectively, and conducted the simulated rill flume(4 m long, 0.12 m wide, 0.1 m height) scouring experiments in laboratory. Flume scouring experiments were carried out under the combinations of 3 slopes(15°, 20 °, 25 °) and 5 flow rates(39.86, 59.98, 79.67, 100.45, 121.16 L/min) with 3 replicates(i.e., a total of 135 scouring experiments). The results showed that soil detachment capacities were significant differences under various vegetations(P<0.05), and ranked as Ophiopogon japonica(2.24 kg/(s·m^2))> bare land(1.34 kg/(s·m^2))> Allium tuberosum(1.09 kg/(s·m^2)). The power functions could be used to describe the relationships of soil detachment capacities with shear stress(R^2=0.75), stream power(R^2=0.73), unit stream power(R^2=0.46) and unit energy(R^2=0.63). The shear stress threshold presented as τ_c Ophiopogon japonicus(8.75 Pa)>τ_c Allium tuberosum(6.47 Pa)>τ_c bare land(1.93 Pa), indicating that vegetation planted in the Terrace Banks in hexagonal prefabricated net format could enhance the soil resistance to detachment.