青海化隆群科新区红层大型滑坡群成因机制研究

Study on formation mechanism of large-scale landslide group in red strata distribution area in Qunke New District,Hualong County,Qinghai Province

青海省化隆群科新区特大滑坡群位于青海省东部,面积约25 km2,垂直落差接近700 m的范围内,广泛分布有大型、特大型滑坡8个,中小型滑坡4个,地质灾害极为发育。该地区地层主要以第三系红层为主,表层多分布有厚度不等的更新世黄土,其中红层有成岩历史短、胶结差,遇水易软化崩解、倾角较缓等特点。坡体在地下水下渗软化和坡脚冲刷作用下,破坏自前缘开始,持续向坡顶扩展,多在坡体形成裂缝和陡坎,沿第三系半成泥岩、粉砂质泥岩界面失稳,顺层滑动,局部表现为切层滑动,形成牵引式滑坡。文中以群科新区大型滑坡群为研究对象,结合地调、钻探、试验等手段,通过定量计算和定性分析相结合,对滑坡的成因机制和稳定性进行分析与评价。研究表明:该类滑坡启动的主要原因为坡脚冲刷引起的溯源破坏,其滑动面受控岩层倾角,多与岩层倾角小角度交叉,地下水对滑带的作用表现为滑坡的多期活动性。由于第三系红层滑坡广泛分布,通过其缓倾顺层滑动及特殊的岩土体特点的研究对滑坡的识别和防治具有指导意义。

The large-scale landslide group in Qunke New District,Hualong County,is located in the east of Qinghai Province,covering an area of about 25 km 2 and a vertical drop of nearly 700 meters.There are 8 large and super large scale landslides and 4 small and medium-sized landslides widely distributed,with extremely developed geological disasters.Tertiary red strata are widely distributed in Hualong County,Qinghai Province.It has the characteristics of short diagenetic history,poor cementation,easy softening and disintegration in water,slow-inclination and so on.Under the action of groundwater infiltration softening and slope toe scouring,the failure of the slope starts from the front edge and continues to expand to the slope top.Cracks and scarps are mostly formed in the slope.It is unstable along the interface of tertiary mudstone and silty mudstone,sliding along the layer,forming a traction landslide.Taking the large landslide group in Qunke District as the research object,combined with geological survey,drilling,laboratory test,the author analyzes and evaluates the formation mechanism and stability of landslide through the combination of quantitative calculation and qualitative analysis of landslide.The research shows that the main reason for the start-up of this kind of landslide is the retrogressive failure caused by slope toe scouring.Its sliding surface is controlled by the dip angle of red strata,and mostly intersects with the dip angle of red strata at a small angle.The effect of groundwater on the sliding surface is manifested in the multi-stage activity of landslide.Due to the wide distribution of Tertiary red rock landslide,the research on its low-angle,sliding along the layer,and special rock and soil characteristics has guiding significance for the identification and prevention of landslide.