工程措施条件下堆积体坡面土壤侵蚀水动力学特性

Hydrodynamic characteristics of soil erosion on deposit slope under engineering measures

工程堆积体极易产生水土流失,及时有效的防护措施是防治水土流失的关键。研究不同工程措施条件下土壤侵蚀过程水动力学参数,可为不同防护措施的选择提供理论参考。该文采用40 L/min流量,对24°、28°、32°共3个坡度的鱼鳞坑和水平阶2种措施条件下的堆积体边坡进行模拟放水冲刷试验,选取水流剪切力、径流功率、径流动能等参数进行分析。结果表明:在试验条件下,2种措施降低了土壤的可蚀性,使土壤的抗蚀性增强;土壤剥蚀率与水流剪切力和径流功率之间存在良好的线性函数关系;土壤剥蚀率与径流动能之间存在良好的对数函数关系;在鱼鳞坑措施条件下,土壤可蚀性参数分别为1×10-3s/m和2.6×10-3s2/m2;在水平阶措施条件下,土壤可蚀性参数分别为5×10-4s/m和1.7×10-3s2/m2;径流功率是描述土壤侵蚀过程的最佳参数;在同一坡面,水平阶措施防护效果优于鱼鳞坑,但2种措施的防护效益均具有时效性。

Engineering deposit formed during the process of engineering construction has unique soil composition and complex underlying surface. This sort of deposit is characterized by weak anti-scourabilty due to loose texture, which may cause severe soil erosion. Hydrodynamic parameters and their relationships with runoff in steep engineering slope show different characteristics in response to hydrodynamic conditions. Most physically based soil erosion prediction models established so far are on the basis of hydraulic characteristics. A detailed study of the hydrodynamic characteristics is the precondition and foundation to understand erosion processes on engineering deposit. Study on the characteristics of hydrodynamic parameters of soil erosion on deposit slope under different engineering measures would be helpful to provide an optional theoretical reference for selection of suitable measures.Moreover,in order to explore the optimal hydrodynamic parameters for describing the process of soil erosion under different engineering measures（ fish-scale pit and level terrace）,a field scouring-erosionexperiment was conducted on steep slopes under three slope gradients of 24°,28° and 32°. Runoff kinetic energy,flow shear stress and runoff power were selected as main parameters to analyze the hydraulic process of rill flow stripping surface soil particles. Results showed that on slopes under measures of fish-scale pit and level terrace,soil erosion amount was reduced because of higher soil antierodibility. Soil detachment rate showed a good linear relationship with both flow shear stress and stream power,while it had a logarithmic relationship with flow kinetic energy. The rill erodibility of engineering deposit under the condition of fish-scale pit was calculated to be 1 × 10^- 3s / m and 2. 6 × 10^- 3s^2/ m^2,and the rill erodibility of engineering deposit under the condition of level terrace was calculated to be 5 ×10^- 4s / m and 1. 7 × 10^- 3s^2/ m^2. Under the same slope of engineering deposit,protection of level terrace was better than that of fish-scale pit,but the effects of these two measures had limitation in time.