【作者】 刘丹丹；

【导师】 王兆印；

【作者基本信息】 清华大学 ， 水利工程， 2010， 硕士

【摘要】 颗粒侵蚀发生在干旱河谷地区,是裸露的岩石发生破碎,呈颗粒状剥离沿坡面滚落,在坡脚形成碎屑堆积体的现象。岩石裸露是发生颗粒侵蚀的首要条件,小江流域许多崩塌滑坡和人类活动造成的岩石裸露最终发育成颗粒侵蚀体。但是颗粒侵蚀引起关注,则是由于汶川地震发生后,岷江沿岸无数的山体崩塌与滑坡造成了大片完全裸露的山体,使得颗粒侵蚀面积急剧扩大。本文以云南省小江流域的颗粒侵蚀为调查研究对象,通过野外测量和试验得到了颗粒侵蚀的基本特征及相关发育机理,初步开展了针对颗粒侵蚀的治理方法研究。小江流域颗粒侵蚀分布于布于干旱河谷区海拔800-2000m的阳坡、半阳坡地带,岩性以细砂岩、千枚岩、板岩、页岩和灰岩为主。颗粒侵蚀的存在形式为颗粒侵蚀体,由坡度常年为50°-70°的裸露侵蚀面、40°左右的颗粒滑动段、35°左右的颗粒堆积体三部分组成。相比于其它侵蚀形式,颗粒侵蚀粒径分布均匀,呈现出较好的分选性,粒径变幅小。颗粒侵蚀的侵蚀强度很大,侵蚀速率主要为在1~10cm/yr,严重破坏植被,带来飞石灾害,并导致坡面泥石流。颗粒侵蚀的发育过程受到干旱河谷气候环境和地形地质的综合影响。气候因素的影响尤为重要,主要是气温与湿度的变化,以及太阳辐射。风是侵蚀发育的主要驱动力,模拟风动力实验证明:单位面积内平均每分钟的吹落量与风速的四次方呈正比关系,同等时段内吹落颗粒的最大均值粒径与风速呈线性关系。颗粒侵蚀的治理必须从侵蚀面开始。选择当地耐旱的苔藓植物种类,与底泥和营养物质混合后均匀涂抹、喷洒于侵蚀面上。苔藓覆盖层可以抵抗阳光暴晒和风吹剥落,在经过雨季的活力生长期和旱季的生长休眠期,苔藓发育到一定程度即可实现治理。更多还原

【Abstract】 Grain erosion is defined as the phenomenon of detachment of grains from bare rocks, flow of grains down slope, and accumulation at the toe of the mountain, forming a deposit fan. The prerequisites of grain erosion development is bare rocks. Bare rocks were caused by avalanches, landslides and human activities, which were very common in the Xiaojing River basin. The Wenchuan Earthquake, occured in Sichuan on May 12, 2008, caused numerous rockfalls, avalanches and landsildes. Consequently grain erosion occurred throughout the earthquake area in dry valley of Min River. The process of grain erosion, and control strategies to limit it are studied by field investigations and experiments in the dry valley of Xiaojiang River basin in southwest China.Grain erosion occurs in the Xiaojiang River Basin mainly on south facing slopes with altitude ranges from 800m to 2000m. In general, grain erosion occurred mostly in finestone, phylite, slate, shale and limestone rocks. A grain erosion site mainly consists of three sections: a top where surface grain erosion occurs with the slope angle in the range of 50°-70°; a middle where grain flow occurs with a slope angle about 40°; and a bottom where deposit fan forms with the slope angle about 35°. Relatively uniform grain size and lack of large stones are common features of grain erosion, which are much different from those of landslides and avalanches. The rate of grain erosion in the Xiaojing River basin is mainly between 1 to 10 cm/yr. Grain erosion causes flying stones and can injure humans, and results in great damages on vegetation and numerous slope debris flows.The develope process of grain erosion is impacted by the combined action of climate, geology and landform. The foremost influence factor is climate, especially the variation of temperature and humidity, and the solar-radiation. Rocks are broken down to grains under the action of insolation and temperature change. Then, wind blows the grains from the bare rock down slope. An experiment was conducted to study the relation of grains blown down by wind with wind speed. Experimental results showed that the amount of grains blown down by wind per area of rock surface per unit time is proportional to the fourth power of the wind speed. However, the size of the grains blown down by wind increases linearly with the wind speed.Several experiments proved that grain erosion can be controlled if the bare rocks are covered with a layer of clay suspension with moss. Two drought-enduring moss species were collected from local and neighboring areas and mixed with mixed with the river sediment and humus, and evenly scrawled or sprayed to the bare rocks. The moss layer protected the rocks from insolation and mitigated the effects of temperature change, thus effectively mitigated grain erosion.更多还原