含砾石锥状工程堆积体侵蚀水动力学特性和细沟形态特征

采用人工模拟降雨的方法,以陕西关中地区的重质土壤和工程中常见的破口石为试验材料,模拟散乱锥状工程堆积体的堆积过程和堆积形态,研究了不同砾石质量含量(0,10%,20%,30%,40%)散乱锥状工程堆积体在不同降雨强度下(1.0,1.5,2.0,2.5mm/min)的侵蚀水动力学特性和细沟形态特征。结果表明:(1)流速和径流强度随雨强的增加而增大,随砾石含量的增加而减小,雨强和砾石对两者均有显著影响,其中雨强的影响较大,起控制性作用;(2)坡面径流处于层流、缓流的状态,雷诺数和弗劳德数随雨强的增加而增大,随砾石含量的增加而减小;(3)剥蚀率随雨强的增加呈指数型增大,相同降雨强度下,随砾石含量的增加线性减小,径流剪切力、水流功率、单位水流功率、过水断面单位能与剥蚀率显著相关且呈幂函数的关系,其中水流功率相关性最好,拟合优度最高,是描述侵蚀动力机制的最优因子;(4)随着降雨强度的增加,细沟出现的时间提前,沟宽、沟深、沟长和细沟密度逐渐增加,雨强相同时,随着砾石含量的增加,细沟出现的时间推迟,且逐渐变窄、变浅,细沟下切侵蚀减弱。

Characteristics of Hydrodynamics and Rill Morphology of Tapered Engineering Piles with Gravel

Engineering piles is a special man-made geomorphic unit and has been found much more serious in soil erosion. The studying of hydrodynamic process in the engineering piles is of great necessity, for the engineering piles with three-dimensional is quite different from the traditional slope. In this paper, a self-made platform was used to simulate the three-dimensional pyramidal engineering piles and an indoor artificially simulated rainfall experiment was carried out under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm/min) to study the hydrodynamic process and shape characteristics of rills of engineering piles with different mass percentage of gravel (0, 10%, 20%, 30%, 40%). The results showed that: (1) Flow velocity and runoff intensity increased with the increase of rain intensities and decreased with the increase of gravel contents. Both the rainfall intensity and gravel contents had the significant influences on flow velocity and runoff intensity, and the influence of rainfall intensity was greater. (2) The runoff was in the laminar and subcritical flow state, and Reynolds number and Froude number increased with the increase of rain intensities and decreased with the increase of gravel contents. (3) Erosion detachment rate increased exponentially with the increase of rainfall intensities, and decreased linearly with the increase of gravel contents, there were significant power function relationships between erosion detachment rate and shear stress, stream power, unit flow power and unit energy of water-carrying, among which stream power had the best correlationship, indicating it was the optimal factor to describe soil erosion. (4) The rill occurring time advanced and the length, width, depth of rill increased with rainfall intensities increasing, while the rill occurring time was delayed, the depth and width of rill decreased gradually with the increase of gravel contents under the same rainfall intensity.