植被发育斜坡土体中根—土间隙对降雨入渗的贡献

发布时间：2018-11-04 13:54

【摘要】：在自然界中,滑坡与大气降雨有着密切的关系,降雨入渗成为了非饱和土体斜坡失稳主要的诱发因素。据统计数据显示,上世纪中期以来,在强降雨作用下植被发育斜坡区发生失稳事件的频率越来越高,不仅极大的破坏当地的生态平衡、打乱了人们正常的生活规律,而且对人们的生命财产安全构成了严重威胁。随着国民经济和地区基础设施建设的不断发展,涉及斜坡稳定性方面的问题越来越引起工程界的重视。然而,仅仅考虑在降雨条件下植被边坡及浅层稳定性的研究是不完善的,本文以云南省昭通头寨、呈贡段家营以及个旧象冲三个植被发育自然斜坡为研究对象,采用现场和室内试验、统计分析以及数学模型等手段研究植被发育斜坡土体中根-土间隙的导流特性及其对降雨入渗的贡献,同时分析由根-土间隙引起的植被抑制浅层边坡稳定性的变化。本文研究取得的主要成果如下：(1)土体中根系密度随着土层深度增加而急剧减少这一规律普遍存在,其空间分布受植被类型、地质条件、生长时间和气候条件等因素的影响。根-土间隙是植物根系伸展的一种普遍现象,其导流现象具有普遍存在性,不受地域、植被类型、气候条件以及地质条件的限制而广泛存在于斜坡土体中,且随着土体深度的不断增加根-土间隙的导流特性随根系的衰减而减弱。(2)头寨试验区和呈贡段家营试验区土体的物理特征差异明显,且季节的变化对土体的物理特性影响不大。头寨试验区非饱和带土体孔隙度、质量含水率、有机质含量及根系生物量集度均比段家营试验区高,头寨试验区土体具有高孔隙度-低容重-高含水率的物理性质和高有机质含量有关。相同土层深度处,头寨试验区土体的渗透速度始终高于段家营试验区土体的渗透速度,头寨试验区土体的饱和渗透速度与初始渗透速度差异较大,而段家营试验区土体的饱和渗透速度与初始渗透速度波动幅度不大。(3)根-土间隙尺寸的大小对水分下渗的阻力特性的影响与Re有关,间隙尺寸大小对摩擦阻力系数的影响与Re呈正相关性。相比传统的阻力计算经验公式和模型一,改进的KAYS阻力模型对研究根-土间隙流道的阻力特性更贴近实际情况,具有一定的实用性；另外,基于纳维埃-斯托克司方程式二次积分化解得到不同根-土间隙流道内水分下渗速度分布,其结果基于水分动态测量过程,从一定程度上反映了土体水分与根-土间隙的关系。(4)在降雨过程中,植被发育斜坡土体中根-土间隙具有很强的导流特性。头寨试验区和呈贡段家营试验区土体中根-土间隙的导流量分别占总入渗量的72%～82%和54%-70%,由于根-土间隙的存在促进了土体水分的下渗,从而消弱或抑制了地表径流的产生。
[Abstract]:In nature, landslides are closely related to atmospheric rainfall, and rainfall infiltration has become the main inducing factor of slope instability in unsaturated soil. According to statistical data, since the middle of the last century, the frequency of unstable events in slope areas developed by vegetation under the action of heavy rainfall has increased, not only greatly damaging the local ecological balance, but also disrupting people's normal life laws. Moreover, it poses a serious threat to the safety of people's life and property. With the development of national economy and regional infrastructure construction, more and more attention has been paid to slope stability. However, it is not perfect to study the slope and shallow stability of vegetation only under rainfall conditions. This paper takes three natural slopes of vegetation development in Zhaotong Village, Chenggong Duan Ying and Gejiuangchong as research objects. Field and laboratory tests, statistical analysis and mathematical models were used to study the conductivity of root soil gap in slope soil and its contribution to rainfall infiltration. At the same time, the change of stability of shallow slope caused by vegetation caused by root-soil gap is analyzed. The main results obtained in this paper are as follows: (1) the root density in soil decreases sharply with the increase of soil depth, and its spatial distribution is affected by vegetation types and geological conditions. Factors such as growth time and climatic conditions. Root-soil gap is a common phenomenon of plant root extension, and its diversion exists widely in slope soil mass without the restriction of region, vegetation type, climate condition and geological condition. With the increasing of soil depth, the conductivity of root soil gap decreases with the decay of root system. (2) the physical characteristics of soil in Touzhai experimental area and Chenggong Duan Jiaying experimental area are obviously different. The seasonal variation has little effect on the physical properties of soil. The soil porosity, mass moisture content, organic matter content and root biomass concentration of unsaturated zone in Touzhai experimental area were higher than those in Duan Jiaying experimental area. The physical properties of soil in Touzhai experimental area are related to the content of high organic matter, such as high porosity, low bulk density and high water content. At the same soil depth, the infiltration velocity of soil in Touzhai experimental area is always higher than that in Duan Jiaying experimental area, and the saturation permeability velocity of soil in Tou Zhai experimental area is different from that of initial seepage velocity. However, the saturation permeability velocity and initial permeability velocity of soil in Duan Jiaying experimental area fluctuated little. (3) the influence of the size of root soil gap on the resistance characteristics of water infiltration is related to Re. The effect of clearance size on friction resistance coefficient is positively correlated with Re. Compared with the traditional empirical formula and model of resistance calculation, the improved KAYS resistance model is more practical to study the resistance characteristics of root-soil gap passage. In addition, based on the quadratic integral solution of Navier-Stokes equation, the velocity distribution of water infiltration in different root-soil gap channels is obtained, and the results are based on the process of water dynamic measurement. To some extent, it reflects the relationship between soil moisture and root-soil gap. (4) during rainfall, the root soil gap in slope soil developed by vegetation has strong conductivity. In Touzhai Experimental area and Chenggong Duan Jiaying Experimental area, the conductivity of the root soil gap accounts for 72% of the total infiltration volume and 54% to 70% respectively. Because of the existence of the root soil gap, the infiltration of soil water is promoted. This weakens or suppresses the generation of surface runoff.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P642.2

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