红壤工程堆积体坡面径流水动力特性研究

Study on the Dynamic Hydrodynamic Characteristics of Runoff on the Slope of Red Soil Engineering Accumulation

[目的]揭示裸坡和土石混合2种典型人为扰动工程堆积体在降雨条件下的坡面径流水动力参数特征,量化堆积体侵蚀动力临界条件,进而为阐明堆积体侵蚀动力机制奠定基础。[方法]以红壤工程堆积体为研究对象,通过模拟降雨试验,开展裸坡和土石混合(20%砾石含量)堆积体在不同降雨强度条件下的径流水动力特性分析,进一步量化不同堆积体侵蚀临界动力条件,开展堆积体侵蚀内在机制研究。[结果]随降雨强度1.0 mm/min递增至2.0 mm/min,堆积体的径流由层流缓流过渡为层流急流,砾石使平均阻力系数增大1.40~3.54倍。径流剪切力和径流功率随降雨强度增大呈递增趋势,1.0 mm/min雨强时砾石作用使径流剪切力均值较裸坡下降44.99%,但≥1.5 mm/min时增大2.90%~18.50%,然而3种降雨强度下砾石均使径流功率均值较裸坡减少10.38%~68.13%,同时单位径流功率及过水断面单位能分别减少20.11%~40.45%和21.06%~37.57%。径流功率是表征堆积体侵蚀动态变化的最优参数,≤1.5 mm/min雨强时砾石抑制堆积体侵蚀,临界径流功率提高19.38%~138.12%,土体可蚀性降低79.87%~83.51%,雨强达到2.0 mm/min时,临界径流功率减小97.87%,土体可蚀性增大347.43%。[结论]降雨强度对裸坡和土石混合堆积体水动力参数均有显著影响,但随降雨强度增大砾石对堆积体侵蚀调控作用会发生改变,存在临界降雨强度。

[Objective]The aim of this study are to explore the characteristics of hydrodynamic parameters on the slope runoff of two typical artificial disturbance engineering accumulations,bare slope and soil rock mixture under rainfall conditions,to quantify the critical conditions for erosion dynamics of accumulations,and to lie the foundation for elucidating the erosion dynamics mechanism of accumulations.[Methods]This study focused on the loose red soil engineering accumulation as the research object.The runoff dynamic hydrodynamic characteristics of bare slope and mixed soil and rock accumulation(20%gravel content)under different rainfall intensity conditions through simulated rainfall experiments were analyzed.The critical dynamic conditions for erosion of different accumulations were quantified.The research on the internal mechanisms of accumulation erosion was conducted.[Results]The runoff of accumulations changed from laminar slow flow to laminar jet flow,and Darcy-Weisbach increased by 1.40~3.54 times,with the increase of rainfall intensity from 1.0 mm/min to 2.0 mm/min.The runoff shear stress and runoff power of the accumulation showed an overall increasing trend with the increase of rainfall intensity.When the rainfall intensity was 1.0 mm/min,the average runoff shear stress of the soil rock mixed accumulation decreased by 44.99%compared to the bare slope.However,when the rainfall intensity was more than 1.5 mm/min,it increased by 2.90%~18.50%.The gravel action reduced the average runoff power by 10.38%~68.13%compared to bare slopes under three rainfall intensities.The gravel action also reduced the unit runoff power and the unit energy of the water flow section by 20.11%~40.45%and 21.06%~37.57%,respectively.The runoff power parameter was used to characterize the dynamic changes of slope erosion in accumulations.When the rainfall intensity was less than 1.5 mm/min,gravel could inhibit accumulation erosion,and the critical runoff power increased by 19.38%~138.12%,resulting in a decrease of 79.87%~83.51%in soil erodibility.When the rainfall intensity reached up to 2.0 mm/min,the critical runoff power decreased by 97.87%,and the soil erodibility increased by 347.43%.[Conclusion]Rainfall intensity has a significant impact on the hydrodynamic parameters of both bare slopes and mixed soil and rock accumulations.However,as rainfall intensity increases,the role of gravel in regulating erosion of the accumulations will change,a critical rainfall intensity can be indentified.