寒旱区路基复合侵蚀破坏机理的微细观试验研究

发布时间：2018-06-10 12:18

本文选题：环境岩土工程 + 复合侵蚀　；参考：《内蒙古工业大学》2014年硕士论文

【摘要】：内蒙古自治区位于干旱寒冷的中国北方，因全年大风日数、沙尘暴日数、积雪日数较多，加之常年平均气温较低、温差变化较大，使得沙漠公路在风沙、风雪、风雨等恶劣的自然环境下，不可避免地遭受着风携沙、风吹雪、风驱雨等复合侵蚀作用。本文主要以沙漠风沙土路基作为研究对象，以不设边坡防护作为最不利情况进行研究。通过风携沙粒子、风吹雪粒子、风驱雨滴粒子的风洞高速摄影试验，研究风携带下的不同粒子与路基边坡撞击瞬间的相互作用；研究路基断面设计参数对粒子撞击路基边坡的位置、撞击瞬间的角度和速度的影响。对于同种粒子，当风速一定，路基填料含水率一定时，路基模型为矮路基，边坡坡率越缓，则大粒子大部分撞击在坡中上部后回弹并继续从路基顶面越过，而小粒子大部分越过路基顶面；路基模型为高路基，，边坡坡率越缓，大粒子大部分撞击在路基边坡经多次向上反弹后能量逐渐损失，沿坡面下滑或粒子反弹后直接飞向路基坡脚处堆积，而小粒子大部分附着在坡面上。对于同种粒子，路基模型的各种参数相同时，路基填料含水率增大，导致沙粒子和雪粒子附着在路基坡面的粒子增多，雨滴粒子渗入路基减少，很快形成冲刷路基现象。通过改变路基中心线与来风向的夹角，利用风洞高速摄影试验，对不同夹角下各种粒子运动轨迹进行研究。路基模型的各种参数相同时，当路基中心线与来风向的交角变小时，在路基坡面处形成的涡流小，路基填料被风卷走的也就减少了，沙粒子打击在坡肩回弹后越过路基，或者粒子堆积坡脚处减少，对路基的风蚀侵害变小。雪粒子附着在坡面上增多，考虑温度的变化则会对路基造成因积雪融化渗入路基内部而引发冻融循环破坏，或融水坡面径流侵蚀破坏，而风驱雨滴粒子打在坡脚处的雨滴减少，对路基的雨滴凿蚀破坏减小。以风吹雪粒子可能引发的冻融风蚀复合侵蚀为例，通过体视显微镜进行微观扫描，研究路基在冻融风蚀复合侵蚀作用下对路基的破坏机理。利用Micrograph图片分析软件提取路基土冻融风蚀前后微观孔隙结构参数，分析冻融循环次数、路基土含水率、风蚀作用对路基各试验层孔隙面积的影响。当路基填料含水率一定，随着冻融次数的增加，对路基坡面表层侵蚀破坏越大，随着水平测试深度增加，由坡面向内部侵蚀作用减小。冻融后继续进行吹蚀路基，路基在复合侵蚀作用下，坡面的破坏更为严重，尤其对路基坡肩的影响最为严重。
[Abstract]:The Inner Mongolia Autonomous region is located in the arid and cold north of China. Due to the number of windy days, the days of sandstorms and the number of snow days throughout the year, coupled with the relatively low annual average temperature and the large variation of temperature differences, the desert roads are windy, sandy and snowy. Under the adverse natural environment such as wind and rain, it is inevitable to be subjected to the combined erosion of wind and sand, wind and snow, wind and rain, etc. In this paper, the sand and sand subgrade in the desert is taken as the research object and the slope protection is the most unfavorable condition. Through the wind tunnel high-speed photography test of wind sand carrying particles, wind snow particles, wind dripping raindrops particles, the interaction between different particles carried by wind and embankment slope impact moment was studied. The influence of design parameters of roadbed section on the position, angle and velocity of particle impact on embankment slope is studied. For the same kind of particles, when the wind speed is constant and the moisture content of the subgrade filler is constant, the roadbed model is low subgrade, and the slope ratio of the side slope is slower, then most of the particles will bounce back in the middle and upper part of the slope and continue to cross from the top of the roadbed. However, most of the small particles cross the top surface of the roadbed, the roadbed model is high subgrade, the slope ratio of the side slope is slower, the energy of the subgrade slope is gradually lost after most of the particles impact on the embankment slope after several times bouncing upward. After falling or bouncing along the slope, the particles will pile up directly to the foot of the embankment slope, while most of the small particles will adhere to the slope. For the same particle, when the parameters of the subgrade model are the same, the moisture content of the subgrade filler increases, resulting in the increase of the particles of sand and snow particles attached to the embankment slope, and the decrease of the infiltration of raindrops into the roadbed. By changing the angle between the center line of the roadbed and the direction of the wind, and using the high-speed photography test of the wind tunnel, the motion trajectories of various particles at different angles are studied. When the parameters of the roadbed model are the same, when the angle between the center line of the subgrade and the direction of the wind changes, the eddy current formed at the slope of the roadbed is small, and the filling of the roadbed is reduced by the wind, and the sand particles strike the embankment and bounce back over the roadbed after the shoulder of the slope. Or particle accumulation at the foot of the slope to reduce the roadbed wind erosion damage becomes smaller. When snow particles are attached to the slope surface, considering the change of temperature, the subgrade will be damaged by freeze-thaw cycle due to the melting of snow and infiltration into the subgrade, or runoff erosion damage will be caused by the melting water sloping surface, while the raindrop droplets driven by wind will decrease at the foot of the slope. Taking the wind-thawing composite erosion caused by wind-blown snow particles as an example, the failure mechanism of roadbed under the combined erosion of freeze-thaw wind erosion is studied by microscopic scanning of stereomicroscope. The micro-pore structure parameters of roadbed soil before and after freeze-thaw wind erosion were extracted by Micrograph image analysis software. The effects of freeze-thaw cycle times, soil moisture content and wind erosion on the pore area of each test layer of roadbed were analyzed. With the increase of freezing and thawing times, the surface erosion damage of embankment slope is greater, and with the increase of horizontal testing depth, the erosion effect from slope to interior decreases with the constant moisture content of subgrade filler. After freezing and thawing, the roadbed continues to be blown away, and the damage of the slope surface is more serious, especially on the shoulder of the embankment under the action of composite erosion.
【学位授予单位】：内蒙古工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

【参考文献】