黄土区原状土壤分离过程的水动力学机理研究

Study on Hydro-dynamic Mechanism of Natural Soil Detachment in Loess Region

对土壤分离过程进行模拟是建立土壤侵蚀过程模型的基础.利用变坡实验水槽,在较大流量(0.5～2.0 L/s)和坡度(8.8%～46.6%)范围内,系统研究了黄土区原状土壤分离过程的水动力学机理.研究结果表明:原状黄土的分离速率远小于扰动土的分离速率,因此,用原状土研究土壤侵蚀机理是十分必要的;土壤分离速率随着流量和坡度的增大而增大,但增大的形式稍有差异,可以用流量和坡度的幂函数准确模拟土壤分离速率(R2=0.95);用平均流速可以对土壤分离速率进行比较准确的模拟和估算;受径流输沙和土样扰动的影响,国内外扰动土样的土壤可蚀性参数与原状黄土的研究成果差异显著;在水流剪切力、单位水流功率和水流功率3个国际上流行的用于模拟土壤分离过程的水动力学参数中,水流功率与土壤分离速率间的关系最为密切,从而表明土壤侵蚀过程受水流能量大小的控制.

Quantitative simulation on soil detachment rate is the base of process-based soil erosion model development. This study was conducted to analysis hydro-dynamic mechanism of soil detachment process for original soil core in loess region under the large range of flow discharge （0.5-2.0 L/s） and slope gradient （8.8%-46.6%）.The results indicated that detachment rate of disturbed soil is more greater than that of original undisturbed soil caused by the disturbance of soil structure. It is necessary to use original undisturbed soil to investigate the mechanism of soil detachment and soil erosion. Soil detachment rate increased with both flow discharge and slope gradient increasing. However, the regression equations were slightly different between each other. Soil detachment rate can be simulated with power function of flow discharge and slope gradient （R^2 = 0.95）. Due to the influence of sediment transport and soil sample disturbance, erodibility parameter of current study was significantly different with the relative results obtained from disturbed soil samples. Therefore, it is necessary to use original soil sample to simulate soil erosion mechanism. Among three current used hydro-dynamic parameters of shear stress, unit stream power, and stream power, there was closely relationship between soil detachment rate and stream power.