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干热河谷土地整理台地边坡的沟蚀发育过程研究
Alternative TitleDevelopment Processes of Gully Erosion on Land Consolidation Terrace Slopes in Jinsha River Dry-hot Valley Region, Southwest China
杨丹
Subtype博士
Thesis Advisor熊东红
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline土壤学
Keyword土地整理台地边坡 水动力特征 形态特征 沟蚀发育机制 水土耦合作用
Abstract本研究以金沙江干热河谷为研究区,依托中国科学院水利部成都山地灾害与环境研究所与云南省农业科学院合建的元谋干热河谷沟蚀崩塌观测研究站(以下简称“元谋站”),构建原位简易试验小区,并采用野外原位人工降雨模拟试验,研究土壤类型、植被状况影响下土地整理台地边坡的径流水动力过程特征、沟道发育形态特征及其侵蚀产沙过程,同时与未进行土地整理的自然边坡的侵蚀过程进行比较分析,探明影响土地整理台地边坡沟蚀发育的关键因素,揭示土地整理台地边坡的沟蚀发育过程。研究结果对于深刻揭示土地整理台地沟蚀发育形态特征及侵蚀产沙过程机理具有重要意义,有助于探索山区水土耦合作用机制,为有的放矢地采取相应措施防治土地整理台地边坡的沟蚀提供有价值的指导。本研究的主要结论如下:(1)建立了干热河谷土地整理台地边坡沟蚀发育强度分级标准,初步确定了影响台地边坡沟蚀发育形态特征的关键因素。基于野外调查,根据沟道宽度、深度、截面积、面密度和割裂度提出了综合反映沟蚀发育程度的指标——沟蚀发育指数Q,初步确定了台地边坡沟蚀发育强度分级标准为:0<沟蚀发育指数Q≤0.1为微度发育;0.1<沟蚀发育指数Q≤0.2为轻度发育;0.2<沟蚀发育指数Q≤1.0为中度发育;1.0<沟蚀发育指数Q≤2.0为强度发育;沟蚀发育指数Q>2.0为剧烈发育。台地边坡沟蚀发育强度受表观因素和微观因素的共同影响。表观因素主要包括边坡类型、土壤类型、植被状况和汇水状况;微观因素主要包括土壤非毛管孔隙度、颗粒分布不均匀系数、曲率系数、粘聚力、内摩擦角和分散率。(2)查明了典型土地整理台地边坡沟蚀发育水动力过程特征。土地整理显著改变径流水动力特征参数的时间变化规律,增大边坡侵蚀力/阻力系数比。自然边坡水动力参数基本不随降雨时间变化而变化,但土地整理台地边坡水动力参数随降雨时间呈规律性变化。土地整理台地边坡水动力特征参数时间变化规律具有相似性,但不同处理台地边坡水动力参数的大小差异显著。各台地边坡雷诺数、剪切力、径流功率和阻力系数均总体上随时间呈先增大后稳定的变化趋势。台地边坡发生沟蚀的剪切力/阻力系数比介于0.065~0.103之间,径流功率/阻力系数比介于0.009~0.012之间。(3)阐明了典型土地整理台地边坡侵蚀方式及形态特征的演变过程。土地整理台地边坡不同程度的发育细沟侵蚀或切沟侵蚀,其中,燥红土、新成土边坡的侵蚀演变过程为片蚀-细沟侵蚀-切沟侵蚀,变性土边坡侵蚀演变过程为片蚀-泄溜侵蚀-细沟侵蚀。但是,自然边坡在整个降雨过程中以片蚀为主,不发生沟蚀。不同土壤类型、植被状况台地边坡的侵蚀演变过程存在较大差异,各侵蚀阶段(片蚀、细沟侵蚀和切沟侵蚀阶段)所需启动时间及持续时间不同。其中,变性土边坡细沟侵蚀启动所需时间最长,为30 min,明显大于燥红土、新成土边坡的8~10 min 和5 min;保留植被残茬燥红土边坡细沟侵蚀持续时间最长为110 min,明显大于裸露燥红土、新成土和变性土边坡的37、70和90 min。降雨过程中,沟道形态特征(长度、宽度、深度、体积和割裂度)基本随降雨次数呈线性或对数增大。各单次降雨末期,沟道体积和割裂度为新成土>变性土>燥红土,沟道深度为燥红土>新成土>变性土。新成土、变性土沟道发育以平面强度(体积、割裂度)的增大为主,燥红土边坡沟道发育以竖向强度(深度)的增大为主。(4)查明了典型土地整理台地边坡沟蚀发育产沙过程特征。土地整理改变边坡产沙特征的时间变化趋势,显著增大边坡侵蚀产沙量。台地边坡泥沙浓度、输沙率的变化趋势均与降雨时间密切相关,而自然边坡泥沙浓度、输沙率基本不随降雨时间变化,基本稳定在较低水平。台地边坡泥沙浓度、输沙率和侵蚀量分别为自然边坡的10.22~50.20、16.75~56.00和10.51~488.06倍。三种土壤类型台地边坡的侵蚀产沙特征具有显著差异,燥红土、变性土泥沙浓度和输沙率以不同方式在时间上呈减小趋势,而新成土边坡泥沙浓度和输沙率在时间上呈先增大后稳定的变化趋势。但在产沙量的大小上表现为新成土、变性土边坡相对接近,且显著大于燥红土边坡。新成土、变性土泥沙浓度、输沙率和侵蚀量分别为燥红土边坡的3.45~4.91、2.30~3.56、1.04~5.27倍。保留植被残茬显著降低输沙率,但对产沙特征的时间变化规律及泥沙浓度的大小影响较小。两种植被状况边坡泥沙浓度、输沙率均大致在时间上呈逐渐变小的变化趋势。(5)揭示了典型土地整理台地边坡沟蚀发育机理。抗剪强度是影响边坡水动力过程特征、侵蚀形态特征和产沙特征的关键土体性质参数,此外颗粒分布状况和团聚度的影响也较为明显。土体性质的差异使得台地边坡土壤可蚀性(0.456~3.311 g/(N×s))和临界侵蚀力(0~1.698 Pa、0~0.218 N/(m×s))明显大于自然边坡(0.290 g/(N×s)、0.410 Pa、0.053 N/(m×s)),改变侵蚀力/阻力系数动态比,促使台地边坡侵蚀强度远高于自然边坡。台地边坡主控水动力条件的动态变化是影响其侵蚀形态特征及演变过程的关键动力因素。降雨前30 min,沟蚀发育形态特征主要受剪切力控制;降雨后90 min(降雨第30~120 min),沟蚀发育形态特征主要受剪切力和径流功率的共同控制。
Other AbstractA series of easy simulation experimental plots were constructed to study the development processes of gully erosion on land consolidation terrace slopes (LCTSs) based on the field investigation. This study was conducted in Yuanmou Dry-hot Valley Gully Erosion and Collapse Observation Research Station of Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, which was located in Jinsha River Dry-hot Valley Region. This study aimed at revealing the influence of soil types and vegetation conditions on the changing processes of hydrodynamic properties, morphological characteristics and sediment characteristics of gullies on LCTSs, and we studied the changing processes of hydrodynamic properties, morphological characteristics and sediment characteristics on a natural slope which had not been interfered by land consolidation. By comparing the gully development processes on LCTSs with that on a natural slope, the key factors that affect the gully erosion development on LCTSs can be found out. The research results revealed the mechanism of morphological development and sediment yield of gullies on LCTSs and natural slope, which were beneficial to explore the coupling effect of water and soil in mountain area and helpful to take purposeful measures to prevent LCTSs from intense gully erosion. The main conclusions of this study are listed as follows:(1) Classfication criteria for gullies’ morphological development degree on LCTSs, and its main influence factors.According to the field investigations about width, depth, sectional area, areal density and lacerate-degree of gullies, development index of gully erosion Q was considered as the quantitative indicator for division of gullies morphological development degree, and the division criteria were: 02 belonged to extremely intensive development degree.The morphological development degree of gullies on LCTSs was affected by apparent factors and microcosmic factors. Slope type, soil type, vegetation and runoff condition were main apparent factors. Noncapillary porosity, coefficient of uneven distribution of particles, coefficient of curvature, cohesive force, and internal friction angle and dispersion rate of soil were major microcosmic factors.(2) Hydrodynamic properties of gullies on typical LCTSs.Land consolidation changed the varying patterns of hydrodynamic properties over rainfall time, and increased the ratio between runoff erosivity and resistance coefficient. The hydrodynamic properties remained basically stable over the whole test process on the natural slope, however, hydrodynamic properties changed regularly over the rainfall time on LCTSs.Similar change trends with time can be detected for the same hydrodynamic property on LCTSs, and significant difference can also be found for the values of the same hydrodynamic property on LCTSs. Reynolds number, shear stress, stream power and resistance coefficient exhibited to increase firstly and then tended to stable over the whole experimental process on our studied 4 LCTSs. The ratio between shear stress and resistance coefficient were 0.065~0.103, between stream power and resistance coefficient were 0.009~0.012 when gully erosion started on LCTSs.(3) Evolution process of erosion patterns and morphological characteristics on LCTSs.Rill or gully erosion developed in varying degrees on LCTSs, but sheet erosion was the unique pattern on natural slope in our study. The evolution processes of erosion pattern for dry-red soil and entisol were sheet erosion-rill erosion-gully erosion, for vertisols was sheet erosion-slip erosion-rill erosion.The starting time and duration of rill erosion on LCTSs can be affected intensively by soil types and vegetation conditions. The starting time of rill erosion for vertisols was 30 min which was the longest in the 4 LCTSs, in contrast, the starting time were respectively 8~10 min and 5 min for dry-red soil and entisol. As for the duration of rill erosion was 110 min for dry-red soil with vegetation stubble, which was much longer than those of bare dry-red soil, entisol and vertisols.The value of morphological characteristics (length, width, depth, volume and lacerate-degree of gullies) increased in different ways over the experimental time. In the whole experimental process, the volume and lacerate-degree of gullies were all characterized with: entisol >vertisols > dry-red soil, in contrast, the depth of gullies was characterized with: dry-red soil > entisol >vertisols.(4) Sediment yield process characteristics of gully development on LCTSs and natural slope.Land consolidation changed the varying patterns of sediment yielding, and enlarged the amount of sediment. Sediment concentration, transport rate varied depending on rainfall time on LCTSs, but sediment concentration, transport rate did not change with the experimental time and remained at a relatively stable level on natural slope. In whole, the sediment concentration, sediment transport rate and the total amount of erosion of LCTSs were significantly higher than those of natural slope, the former were respectively 10.22~50.20, 16.75~56.00, 10.51~488.06 times as much as the latter.Time changing trends and values of sediment characteristics were significant different among the three soil type LCTSs. It showed a decreasing tendency for sediment concentration and transport rate both in dry-red soil and vertisol. By contrast, sediment concentration and transport rate exhibited to increase firstly and then tended to stable over the test time in entisol. The average value of sediment yield of entisol and vertisol were similar and greater than that of dry-red soil. The sediment concentration, transport rate and total amount of erosion of entisol and vertisol were respectively 3.45~4.91, 2.30~3.56, 1.04~5.27 times as much as dry-red soil.Vegetation stubble can decrease sediment transport rate evidently, but had no significant effects on decreasing sediment concentration and can not change the time trends of sediment concentration and transport rate in this study. Sediment concentration and transport rate all showed to decrease gradually with time under the two vegetation condition LCTSs.(5) Development mechanism of gully erosion on LCTSsThe soil shear strength was the most important soil properties that influenced the hydrodynamic properties, morphological characteristics and sediment yielding process of gullies on our studied slopes. Besides, particle distribution and degree of aggregation of soil can also affect the sediment yield process in this study. The difference of soil properties induced higher soil erodibility (0.456~3.311 g/(N×s)) and critical runoff erosivity(0~1.698 Pa, 0~0.218 N/(m×s)) in LCTSs than those(0.290 g/(N×s), 0.410 Pa, 0.053 N/(m×s)) in natural slope, and changed the dynamic ratio between runoff erosivity and resistance coefficient, which resulted in more severe gully erosion in LCTSs than in natural slope.It was the key factor that affected the evolution processes of erosion modes and morphological characteristics of gully development for the key controlling hydrodynamic properties’ dynamic changing. The key controlling hydrodynamic properties changed from shear stress in the first 30 min to shear stress and runoff power in the last 90 min (30 ~ 120 min).
Pages194
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24587
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
杨丹. 干热河谷土地整理台地边坡的沟蚀发育过程研究[D]. 北京. 中国科学院大学,2017.
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