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喀斯特槽谷区坡面集中水流曼宁系数变化特征
曾荣昌, 李天阳, 何丙辉
西南大学 资源环境学院 三峡库区生态环境教育部重点实验室, 重庆 400715
摘要:
[目的] 探究喀斯特槽谷区不同岩石与坡面夹角影响下地表集中水流阻力变化特征,为该区土壤侵蚀模型构建提供科学依据。[方法] 在3个坡度(10°,15°,20°),3个冲刷流量(5,7.5,10 L/min)和6个岩石与坡面夹角角度(30°,60°,90°,120°,150°,180°)组合条件下开展室内放水冲刷试验,研究喀斯特槽谷区不同岩石与坡面夹角下地表集中水流曼宁系数的变化规律及其影响因素。[结果] ①地表集中水流曼宁系数n随冲刷历时呈迅速增大再缓慢增长或趋于稳定的变化趋势。不同夹角的n值大小顺序为:n180° > n150° > n90° > n30° > n120° > n60°。②当岩石与坡面夹角大于30°时,n与水深h显著相关,夹角为30°时,二者关系不显著;试验条件下,n与雷诺数Re关系不显著,与弗汝德数Fr呈显著幂函数负相关。③相对水深曼宁系数n/h随夹角增大呈先增后减的变化趋势。④岩石与坡面夹角大于30°时,n/h与Re均呈幂函数负相关,夹角为30°时,二者关系不显著;不同岩石与坡面夹角的n/h与Fr关系均不显著。[结论] 喀斯特槽谷区坡面集中水流曼宁系数n受岩石与坡面夹角的显著影响,随夹角增大总体呈先减后增的趋势。
关键词:  喀斯特  岩石与坡面夹角  集中流  曼宁系数
DOI:10.13961/j.cnki.stbctb.2020.04.036
分类号:S157.1
基金项目:国家重点研发计划课题“喀斯特槽谷区土壤地上/下流/漏失过程与保护技术研发及示范”(2016YFC0502303);国家自然科学基金项目“喀斯特槽谷区土壤地上/下流/漏失过程与模拟研究”(41771312)
Manning Roughness Coefficient Characteristics of Concentrated Flow on Slope in Karst Trough Valley Hillslope
Zeng Rongchang, Li Tianyang, He Binghui
College of Resources and Environment, Southwest University, Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing 400715, China
Abstract:
[Objective] The variation characteristics of concentrated water flow resistance influenced by different angles between bedrocks and ground surface on the hillslope were explored to provide scientific basis for the construction of soil erosion model in the karst trough valley area.[Methods] To investigate the changes of Manning roughness coefficient (n) of concentrated flow and its influencing factors on the karst trough valley hillslope with different angles between bedrocks and ground surface, the laboratory scouring simulation experiments were conducted under the conditions of three slope gradients (10°, 15° and 20°), three inflow rates (5, 7.5, 10 L/min) and six angles between bedrocks and ground surface (30°, 60°, 90°, 120°, 150° and 180°) . [Results] ① The Manning coefficient n of concentrated flow increased rapidly and then increased slowly or tended to be stable with the scouring time. The average value of n was ranked as: 180° > 150° > 90° > 30° > 120° > 60°. ② When the angle between rock and slope surface was greater than 30 °, the relationship between n and water depth (h) was significant, and when the angle was 30 °, the relationship between n and Reynolds number (Re) was not significant, and there was a significant negative power function correlation between n and Froude number (Fr). ③ The ratio of Manning roughness coefficient to flow depth (n/h) increased at first and then decreased with the increase of angles between bedrocks and ground surface. ④ The n/h presented negative power correlation with Re when the angle between bedrocks and ground surface was greater than 30 °, and n/h showed no significant relationship with Re when the angle between bedrocks and ground surface was 30°. The relationship between n/h and Fr was always not significant. [Conclusion] Manning coefficient n was strongly affected by the angles between bedrocks and ground surface, and decreased first and then increased with the increase of angles between bedrocks and ground surface on the karst trough valley hillslope.
Key words:  karst  angles between bedrocks and ground surface  concentrated flow  Manning roughness coefficient