2013年1月11日,云南镇雄发生滑坡,滑程近800m,堆积体积约40104m3,赵家沟村民小组60多间房屋被毁, 46人遇难。本文对旱季期间少遇的镇雄赵家沟特大滑坡灾害原因进行了现场调查,运用有限元法分析了久雨和采矿条件下滑坡失稳机理。从地质上,滑坡位于乌蒙山区常见的煤系地层区,上部为陡倾的三叠系中统灰岩、白云岩,中部为相对较陡的三叠系下统砂页岩地层,下部为平缓的二叠系上统页岩、泥岩地层,局部含煤,具有上硬下软的工程地质结构和上部富水下部隔水的水文地质结构,极易形成滑坡地质灾害。在地形上,形似靴状地形,上部陡峭地形导致山体易于失稳,而中下部开阔伸展良好的沟谷提供了远程的运动条件,较大的势能向动能的转化,容易形成高速远程滑动,造成严重的损失。可将滑坡区分成滑坡源区、铲刮与堆积区、滑覆成灾区3部分,其中,高速飞行的滑体直接滑覆了赵家沟村民小组数间民房,同时,其余抛散的滑坡体沿低缓沟谷部位液化滑动冲埋多间村民房屋,成为特大灾害发生的重要原因。有限元模拟结果表明:堆积层斜坡的地下水位上升,可使赵家沟滑坡稳定系数降低10%以上,说明对位于陡坡沟谷中的残坡坡积物来说,持久小雨也可触发滑坡失稳; 由于滑坡下部煤层较薄,顶板地层完整且距滑床厚达200多米,在20世纪60～70年代小煤窑开采情况下,对滑坡变形失稳没有明显影响。通过此次特大滑坡引发的社会问题,作者提出了加强特大地质灾害公共危机管理科学应对、加强煤系地层地区高速远程滑坡早期识别与风险管理和加强复杂地质灾害防灾专业知识培训的建议。
On January 11,2013,a large landslide occurred in Zhenxiong county, Yunnan Province. The debris traveled about 850m. The debris volume was about 400,000m3. More than 60 houses in Zhaojiagou village were destroyed.46 persons were killed by the debris. This paper presents the field investigation on the cause of the landslide which unusually occurred in dry-season. It uses finite element method to analyze the mechanism of landslide under the conditions of long-term rainfall and coal mining. In geology, the landslide site located in coal-related strata which is common in Wu-meng mountains. The upper strata are limestone and dolomite of high bedding dip angles and middle Triassic epoch. The middle strata are sand shale of relatively high bedding dip angles and lower Triassic epoch. The bottom strata are shale and mudstone with coal seams of gentle bedding dip angles and upper Permian epoch. The strata system has an upper hard and lower soft structure in engineering geology and an upper rich and lower poor groundwater structure in hydrogeology. It is very vulnerable to landslide disasters. The site topography looks like a boot-shaped profile from top to bottom. The upper ground is steep and easy to be unstable. The middle and bottom grounds are wide and gentle. The ground profile offers the condition for long run-out motion and makes potential energy to transfer into kinetic energy. Therefore, the site can easily form high-speed and long travel distance landslide that causes disasters. The landslide zone can be divided into landslide source area, shoveling and stripping and deposition area and debris covered village disaster area. The flying landslide debris with high speed directly slipped and covered over the village houses. In the meantime, the rest ejected debris liquefied and rushed and buried other village houses along the gentle stream valley. They became the most important reason for the huge disaster. The finite element simulation results show the following. The rainfall led the groundwater table rising, which caused a more than 10% reduction of the factor of safety value of the slope. This result may demonstrate that the slope colluvium on steep stream valleys can be triggered to fail by long duration of small rainfall. The coal bed beneath the landslide has relatively thin thickness. The vertical distance of the upper strata between the coal seam and the landslide base is about 200m. The coal mining between 1960 and 1970 did not have noticeable effect to the slope deformation and stability. Based on the social problem induced by this landslide disaster, the authors put forward the following suggestions: to reinforce the public risk management and responding of huge geological disaster, to enhance the early recognition of high speed and long travel distance landslides in coal bed related strata areas, to improve the professional training of complex geological disaster prevention.