National Natural Science Foundation of China (No.41771312) and National Key Research Developmental Program of China (No.2016YFC0502303)
喀斯特槽谷区不仅存在地上/地下双层空间结构，还存在典型顺/逆层坡两种特殊的地质构造，因此研究喀斯特槽谷区两翼坡面水流移动规律具有重要意义。根据野外调查结果，在喀斯特槽谷区临界坡度25°条件下进行人工模拟降雨试验，采用顺/逆层坡岩层倾角（30°、60°和90°）和3种雨强（30、60和90 mm•h-1）作为变量因子，并以裸坡作为对照因子，研究喀斯特槽谷区顺/逆层坡面水动力参数特征。结果表明：喀斯特槽谷区顺/逆层坡主要以薄层浅流为主，顺层坡的岩层倾角越大则坡面流速越小，逆层坡则以岩层倾角60°为临界点，裸坡的流速均大于顺/逆层坡。对于喀斯特槽谷区顺层坡而言，其雷诺数Re 和佛汝德数Fr均大于逆层坡而小于裸坡，阻力系数f均小于逆层坡而大于裸坡。雷诺数Re和阻力系数f两个参数呈显著的幂函数正相关关系。地表累积径流量分配比例大小排序为裸坡＞顺层坡＞逆层坡，地下累积径流量分配比例为逆层坡＞裸坡＞顺层坡。本研究可为喀斯特槽谷区顺/逆层坡的坡面的土壤侵蚀预报模型提供科学依据。
【Objective】 A karst valley has not only surface/underground double-layered structure, but also two special geological structures, bedding slope and reverse slope. During rainstorms, bedrocks seem to form a discontinuous impermeable area, which reduces soil and water loss. Although it seems obvious that rock layer inclination influences hydrology in karst areas, little has been reported in the literature on this subject. Therefore it is of great importance to launch a study on rules of water transport with runoff in Karst Valley areas. So the objective of this study is to investigate roles of rock layer inclination in guiding surface water flow on slopes in karst valleys. 【Method】 Based on field investigations, a simulated rainfall experiment, designed to have bedding/reverse slopes (30°, 60° and 90° in gradient), 3 levels of rainfall intensity (30, 60 and 90 mm h-1) and a bare slope as CK, was carried out on a slope approximate to the critical gradient (25°) of the nearby karst valley to explore runoff rate and hydrodynamic parameters and their relationships with bedding/reverse slopes. A total of 18 treatments and 3 duplicates for each were laid out and conducted in the experiment. The characteristics of soil hydraulics measured included flow velocity, Reynolds number (Re), Froude number (Fr), Darcy-Weisbach roughness coefficient (f), and surface/underground accumulated runoff.【Result】Results show that with the rainfall experiment going on, runoff on the bedding slopes and inverse slopes was dominated with shallow watersplash. Over on bedding slopes, the overland flow slowed down in velocity, with rising inclination angle of the rock layer, while on reverse slopes the inclination angle of 60° was the threshold. Surface runoff flew faster on the bare slope than on bedding slopes and reverse slopes. Reynolds number (Re) and Froude number (Fr) was higher on bedding slopes than on reverse slopes, but lower than on bare slopes, Darcy-Weisbach roughness coefficient (f) was lower on bedding slopes than on reverse slopes but higher than on bare slope. Value for Froude number (Fr) indicated that the water flow was a subcritical one, and was generally higher on bare slopes than on bedding slopes and reverse slopes. Darcy-Weisbach roughness coefficient (f) was much lower on bare slopes than on bedding slopes and ireverse slopes, showing order of reverse slope ＞ bedding slope ＞ bare slope, and decreased with increasing Reynolds number (Re), which was in an extremely significant positive power relationship with Reynolds number (Re). Accumulated surface runoff varied with rock layer inclination in the order of bare slope ＞ bedding slope ＞ reverse slope , while accumulated underground runoff followed an order of reverse slope ＞ bare slope ＞ bedding slope.【Conclusion】Overall, the findings may provide certain data support for analysis of the mechanism of runoff generation and scientific basis for further research on processes of the runoff and models of the soil erosion in karst valley areas. Meanwhile, these findings are expected to be of some help for building prediction models for soil erosions in similar environments different in rock layer inclination.
甘凤玲,何丙辉,覃自阳.喀斯特槽谷区的顺/逆层坡面对水动力学参数的影响[J].土壤学报,2019,56(4):825-837. DOI:10.11766/trxb201808210284 GAN Fengling, HE Binghui, QIN Ziyang. Effect of Bedding Slope on Hydrodynamic Parameters in Typical Karst Valley[J]. Acta Pedologica Sinica,2019,56(4):825-837.复制