三峡库区低等级土质道路侵蚀及防护研究

发布时间：2018-01-17 15:32

本文关键词：三峡库区低等级土质道路侵蚀及防护研究　出处：《华中农业大学》2014年博士论文　论文类型：学位论文

【摘要】：道路网络建设和发展是区域经济发展的基础和保障,是促进不同区域之间能流、物流、信息流交换的重要通道。然而道路作为一种纯粹的人为景观,必然对周边生态环境产生影响。在三峡库区,地形起伏大,人为建设活动频繁,道路建设与维修活动所形成的土壤侵蚀已经成为不可忽视的土壤流失类型,影响流域水文过程、受纳水体水质,加速库区淤积,成为一个亟待解决的环境问题。开展道路,尤其是低等级土质道路的侵蚀规律及防护的研究,弄清道路侵蚀-水文过程及其防控途径,对于完善区域-坡面土壤侵蚀过程研究有重要理论意义,对解决三峡库区道路侵蚀防护有重要的实践意义。本文以土质道路为研究对象,将道路系统分解为路堑边坡、路面和路堤边坡,通过设置不同边坡植被防护模式如自然恢复(NR)、草灌结合(GS)、草本(GR)、梯坎＆草灌结合(TGS)、植生带(SS)、坡耕地(FL)、草本坡耕地(GF),结合人工模拟降雨试验、模拟冲刷试验、原位剪切试验等,分析不同植被防护模式对道路路堑和路堤边坡土壤性质改良、强度提升、侵蚀规律和防护等方面影响,遴选出最佳防护模式。通过室内模拟降雨试验,研究不同路面结构降雨产流产沙规律及边沟对路面侵蚀水沙输移影响,借助临时路面径流小区,通过野外自然降雨观测试验,探讨不同交通荷载和雨型等条件下,路面侵蚀及污染物初始冲刷等相关问题。主要研究结果如下：(1)通过在道路边坡进行植物防护和原位剪切试验,研究了不同植被防护措施对边坡抗剪强度(.τ)影响。结果表明,植被根系随土壤深度增加而减少,表层(0-10 cm)根系长度密度(Root length density, RLD)占总RLD的34%-78%；植被根系含量及盖度与土壤水分含量(Soil water content, SWC)呈指数正相关。表层(0-10 cm)土壤抗剪强度主要受植被根系及盖度影响,随着根系长度密度(RLD)、根系重量密度(Root weight density, RWD)、植被盖度(Vegetation cover,VC)增加呈指数形式增大。30 cmm深度土壤抗剪强度值显著低于10 cm值和50 cm值。随着土壤深度增加,土壤容重和水分对抗剪强度影响力增大,在50 cm处两者分别与抗剪强度呈线性正相关和指数负相关关系。(2)边坡植被在经过8个月自然生长之后,选择路堑和路堤30。边坡小区作为模拟降雨对象。试验结果表明：路堑边坡侵蚀量高于路堤边坡侵蚀量。草灌结合措施,由于致密的地表覆盖(盖度91.4%,地上生物量1.44kgm-2)和发育良好的地下根系系统(RWD3.94 kgm-3),径流系数(4.3%)和土壤侵蚀率(1.99 g m-2 min-1)显著低于其它防护措施。虽然植生带措施和草本措施选择相同的品种,但是由于植生带措施尚未完全发育的地下根系(RWD1.50kgm-3, RLD2.11 kmm-3),土壤侵蚀量(38.5 gm-2 min-1)显著高于草本措施。土壤侵蚀量、径流系数等随植被根系含量、地表生物量增加而呈对线下降。模拟降雨前后,草灌结合措施土壤抗剪切强度最高(分别为59.29 kPa和53.73 kPa),其次为草本措施(46.93 kPa和40.48 kPa)和植生带措施(31.20 kPa和18.87 kPa),自然恢复小区最低为25.31 kPa和9.36 kPa。而抗剪强度衰退值相反,自然恢复措施衰退值最高为15.95 kPa,草灌结合最低为5.56 kPa。土壤抗剪强度衰退值与植被根系及地上生物量呈极显著线性负相关。降雨过程中,抗剪强度的变化与侵蚀过程密切相关,抗剪强度衰退值与径流系数呈线性正增长关系与土壤侵蚀率呈幂函数增长关系。(3)通过模拟降雨(雨强90 mm h-1和120mm h-1)与模拟冲刷(放水量15 L min-1和20 L min-1)试验相结合的方式,研究降雨与路面汇水对路堤边坡侵蚀影响。在模拟降雨试验下,草灌结合产流和产沙量最低,截流和拦沙效率显著高于其它防护模式。模拟冲刷试验下,各措施的水文响应要明显比模拟降雨试验下更迅速,初始产流时间更快。相同措施下,模拟冲刷试验下侵蚀量要高于模拟降雨。水稳性团聚体含量、饱和导水率、植被盖度和根系含量在降雨和冲刷试验下均显著影响路堤边坡的土壤侵蚀量。模拟冲刷试验下,草本措施致密的地下根系地面根茎增加入渗量,分散和消弱径流侵蚀力,并提供额外的地表粗糙度,截流拦沙能力高于草灌结合措施,在路堤边坡有集中水流影响下,防护效果最佳。(4)通过模拟降雨试验,研究拱型、侧倾型、平直型和凹型等路形路面侵蚀特征。试验结果显示：路形对侵蚀特征有显著影响,平直型和凹型路面降雨产流量和产流率高于拱型和侧倾型。凹型土壤侵蚀率最高是拱型路面侵蚀率的11～14倍。路形通过改变路面降雨径流水动力学参数来影响侵蚀过程。径流流速、雷诺数和弗洛德数随拱型侧向型平直型凹型迅速增加,而径流深、Darcy-Weisbach阻力系数和曼宁ae率随拱型侧向型平直型凹型依次降低。不同路形条件下,边沟改变路面侵蚀水沙输移特征。拱型路面67%-82%的径流和85%-94%的泥沙是通过两侧边沟输出的,路面输出量比例低；凹型路面90%以上的水沙均通过路面进行输出的,边沟径流输出量仅为3%～5%,泥沙输出量为4%-7%。(5)通过自然降雨观测研究不同交通荷载及雨型条件下路面侵蚀规律和污染物流失特征。研究结果表明,交通荷载大的干道产流率和侵蚀率均高于交通荷载低的支道,对产流率影响显著的因子主要为降雨量,对产沙率影响显著的因子为降雨量、雨强。雨型对污染物的流失特征影响显著,不同雨型下,污染物的浓度峰值和雨强峰值表现出不同的滞后性,氮素的流失以总氮为主,磷素流失则以泥沙结合态为主。雨型影响污染物的初始冲刷特征,泥沙的初始冲刷强度较弱,而总氮、铵态氮、泥沙结合态磷和溶解态磷均发生了强度较大的初始冲刷效应。本试验结果虽然仅来自于三峡库区较小研究区域内,但是相关试验结果能适用于国内外其它相似环境。对类似低等级土质道路的设计、施工及管理提供必要的理论解释。试验结果中有一些还待进一步的研究(如土质道路初始冲刷定义等),便于更好的服务于流域侵蚀管理和水文水质安全。
[Abstract]:The road network construction and development is the foundation and guarantee of regional economic development, is to promote inter regional flow, logistics, information flow exchange important channel. However, the road as a purely man-made landscape, the inevitable impact on the surrounding ecological environment. In the Three Gorges Reservoir area, terrain fluctuation, human construction activities, soil erosion formed by road construction and maintenance activities have become the noticeable loss of soil types, influence the hydrological process, the water quality of receiving water, accelerate the reservoir, become an urgent environmental problem. The development of the road, especially the study of erosion and protection of low grade unpaved roads, clear road erosion the hydrological process and its prevention and control, to improve the region has important theoretical significance for studying soil erosion process of slope, to solve the road erosion in Three Gorges Reservoir area has important practical significance for the protection. The road to the soil as the research object, the system is divided into road slope and road embankment slope, by setting different slope vegetation protection modes such as natural recovery (NR), (GS), combination of grass and shrub herb (GR), terrace & grass shrub combination (TGS), vegetation (SS) (FL), slope farmland, farmland herb (GF), combined with the artificial rainfall simulation experiment, simulation of scouring, in-situ shear test, analysis of the protection mode of different vegetation on road cut slope and embankment slope soil properties improvement, increase strength, erosion and protection and other aspects, select the best protection pattern through. Indoor rainfall simulation experiment of different pavement runoff law and ditch erosion of water and sediment transportation on the road, with the runoff of temporary pavement, through field observation experiment on natural rainfall, different traffic loads and rain conditions, surface erosion and pollutants The initial problems related to erosion. The main results are as follows: (1) through the door and in situ shear test plants in road slope, the protective measures of different vegetation on the shear strength of the slope (. T) effect. The results showed that the vegetation roots decreased with increasing soil depth, the surface (0-10 cm) root length density (Root length density, RLD) the total RLD of 34%-78%; the content and coverage of vegetation roots and soil moisture content (Soil water, content, SWC) were positively correlated (0-10 cm). The surface strength is mainly affected by the vegetation cover of the root and influence of soil shear, with root length density (RLD), root weight density (Root weight density, RWD), vegetation coverage (Vegetation cover, VC) increased exponentially with the increase of.30 CMM depth of soil shear strength was significantly lower than that of 10 cm and 50 cm value. With the increase of soil depth, soil bulk density and moisture content on the shear strength. The force increases at 50 cm respectively and the shear strength index showed a linear positive correlation and negative correlation. (2) slope vegetation after 8 months of natural growth, choose to cut and fill 30. slope area as rainfall simulation object. The experimental results show that the slope erosion is higher than that of embankment slope erosion the grass. Combining irrigation measures, due to the dense surface coverage (coverage 91.4%, ground biomass 1.44kgm-2) and well-developed root system (RWD3.94 kgm-3) (4.3%), runoff coefficient and soil erosion rate (1.99 g m-2 min-1) was significantly lower than that of the protective measures. Although the vegetation measures and herb selection measures the same species, but due to the underground root vegetation measures are not yet fully developed (RWD1.50kgm-3, RLD2.11, kmm-3), the amount of soil erosion (38.5 GM-2 min-1) was significantly higher than that of herbaceous measures. The amount of soil erosion, runoff coefficient with vegetation root The content of above ground biomass increased on line drop. The simulated rainfall after grass irrigation combined with measures of soil anti shearing strength is the highest (59.29 kPa and 53.73 kPa), followed by herbal measures (46.93 kPa and 40.48 kPa) and vegetation measures (31.20 kPa and 18.87 kPa), the natural restoration area minimum 25.31 kPa and 9.36 kPa., while the shear strength value decline instead, natural restoration measures decline value of up to 15.95 kPa, with a minimum of 5.56 kPa. of shrub and grass soil shear strength decline were significantly linear and vegetation root and aboveground biomass negatively. During rainfall process, closely related to changes in shear strength with the erosion process, the shear strength of the recession were linear positive relationship with the growth rate of soil erosion in a power function relationship with the runoff coefficient of growth. (3) by simulated rainfall (rainfall intensity of 90 mm H-1 and 120mm h-1) and simulation (15 L min-1 scouring water discharge and 20 L min-1) test. Combination effects of rainfall and road embankment slope erosion in the catchment. The simulated rainfall experiment, combining irrigation grass runoff and sediment yield was the lowest, and the closure of sediment efficiency was significantly higher than that of other protective mode. Simulation washout test, the response to hydrological measures than simulated rainfall experiment more quickly the initial runoff time faster. The same measures under the simulated scouring experiment under simulated rainfall. Soil erosion amount is higher than the content of water stable aggregates, saturated hydraulic conductivity, vegetation coverage and root content in rainfall and erosion tests have significant influences on erosion of embankment slope soil erosion experiment. Simulation under ground rhizome herb roots dense measures to increase the amount of infiltration, runoff erosivity dispersion and extinction, and provide additional surface roughness, sediment interception capacity is higher than that of shrub and grass combined measures have concentrated flow effect in embankment slope under the protective effect The best result. (4) through the rainfall simulation experiment, research of arch type, roll type, flat type and concave shaped road pavement erosion characteristics. Experimental results show that the road shape has a significant influence on the soil erosion characteristics, flat and concave road rainfall runoff and runoff rate is higher than the arch and roll type concave. The soil erosion rate is the highest arch pavement erosion rate of 11 ~ 14 times. The road shape by changing the surface runoff kinetic parameters to influence the erosion process. Runoff velocity, Reynolds number and Flood number increases rapidly with the lateral arch type flat type concave type, and runoff depth, the drag coefficient Darcy-Weisbach and Manning AE rate with arch lateral type flat type concave shape decreased. Different road conditions, side ditch erosion change water and sediment transport characteristics of road pavement. Arch 67%-82% and 85%-94% runoff sediment is through the two side channel output, the proportion of pavement output is low; the concave surface 90% Above the water through sand road side ditch runoff output, output is only 3% ~ 5%, the sediment output was 4%-7%. (5) through the observation and study of natural rainfall in different road traffic load and under the condition of rain erosion rules and pollution characteristics. The results show that the traffic load of the road runoff rate and the erosion rate was higher than that of road traffic load is low, significantly influencing factors of runoff rate is mainly on rainfall, sediment yield significantly influence factor of rainfall, rainfall intensity. The loss characteristics of rain type of pollutants significantly affect the different types of rain, the pollutant concentration peak and peak showed different rain intensity the lag, the loss of nitrogen to total nitrogen and phosphorus loss in sediment bound pollutants. The initial scour characteristics of rain type, initial sediment erosion intensity is weak, while the total nitrogen, ammonium nitrogen, phosphorus and dissolved with sediment P had the first flush effect of greater strength. The result although only from the Three Gorges Reservoir area is smaller in the study area, but the test results can be applied to other domestic and foreign environment. Similar to the design of similar low levels of unpaved roads, construction and management to provide the necessary theoretical explanation. The experimental results in some further the research (such as soil erosion, such as the definition of the initial road) to better serve the watershed erosion management and hydrology and water quality safety.

【学位授予单位】：华中农业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U418;S157

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