摘要
隆德县地处黄土高原西部,六盘山主峰西侧,该区自然环境脆弱,地质条件复杂,是宁夏地质灾害的易发区。本文基于野外地质灾害详细调查和室内试验研究,分析了隆德县坡面型泥石流的形成机理。研究结果表明：隆德县坡面型泥石流主要发育在新近系（Ngn）桔红色砂质泥岩地层中,且厚度小（0.5~2 m）,坡度大（40°~50°）,坡面风化的泥岩残坡积物构成主要物源。该泥岩残坡积物粘粒（d〈2μm）含量较多（25.4%）且具有弱膨胀性,吸水后会发生一定程度的崩解软化,导致土体结构联结减弱、强度衰减。降雨是隆德县坡面型泥石流最主要的触发因素。本文通过研究含水量、膨胀压力和强度之间的关系,得到了该岩性边坡的稳定性评价模式,由计算可知,当饱和度达到约85%时,坡体处于临界稳定状态。遇到持续性降雨或暴雨作用,残坡积物失稳下滑,在坡面水流的作用下形成坡面型泥石流。
Longde county is located in the west of Loess Plateau,Liu-p＇an Mountains＇ peak on its west. The natural environment of this region is fragile,while the geological condition is also complicated. In the matter of geological hazards,Longde county is in the severe situation in Ningxia. Based on the survey of geological hazards and lab tests,the formation mechanism of the debris flow on slope in Longde county has been studied in this paper. The research results indicate that the lithology of debris flow on slope in Longde county,which is developed on the steep slope（ 40° ~ 50°） with shallow soil（ 0. 5 ~ 2 m） and whose main material source is the loose weathered mudstone residual soil in the surface of slope,is mainly the orange sandy mudstone of Neogene（ Ngn）. This residual soil consists of some clay particles,whose diameter is less than 2 μm and quality accounts for 25. 4%,and has the weak dilatability. A certain degree of degradation and softening will occur in this residual soil after immersed by water,resulting in the connection of structure and strength of the soil become weakened. In addition,rainfall is the most important trigger factors of the slope mudflow. In this paper,the stability evaluation model is achieved by analyzing the relationship of moisture content,expansion pressure and the strength. Through this model,when soil saturation is about 85%,the slope is in the critical state. Then suffering from the persistent rain or rainstorm,the residual soil will slide. Further,with the work of slope runoff,the debris flow on slope will occur.
出处
《中国地质灾害与防治学报》
CSCD
2016年第1期49-54,61,共7页
The Chinese Journal of Geological Hazard and Control
基金
中国地质调查局项目"西北黄土高原区地质灾害详细调查"(12120108914028)
关键词
坡面型泥石流
泥岩
残坡积物
形成机理
隆德县
debris flow on slope
mudstone
residual soil
formation mechanism
Longde county
