典型黄土丘陵区浅层黄土滑坡稳定性评价——以延安市志丹县为例

Evalution of shallow loess landslide stability in typical loess hilly region:A case study of Zhidan County in Yan'an area of Shaanxi Province

黄土丘陵地区地质环境脆弱,每到雨季极易诱发浅层黄土滑坡,对居民的生命和财产安全构成威胁也阻碍着当地经济的发展。对浅层滑坡进行稳定性评价,不仅有助于认识浅层滑坡的发生发展过程,而且对防灾减灾和地区规划建设具有十分重要的指导意义。本研究选择SINMAP模型作为评价浅层黄土滑坡的重要工具,评价了陕西省延安市志丹县黄土丘陵区浅层滑坡的稳定性,评价结果表明:1)研究区整体稳定性程度较高,在降雨量为8.6 mm、15 mm、25 mm、50 mm和100 mm时不稳定区域(包括极不稳定、不稳定和潜在不稳定)面积分别占研究区总面积的9.12%、18.93%、23.17%、30.94%和38.67%,不稳定区域的面积不超过整个研究区面积的一半,极不稳定区域的滑坡密度最大,其次为不稳定区域和潜在不稳定区域;2)随着降雨量的增大,潜在不稳定和不稳定区域的面积会逐渐扩大,极不稳定区始终位于坡度大且水流侵蚀强烈的地方,变化幅度小;3)浅层滑坡的稳定性很大程度上依赖于当地的地形条件:坡度分布为20°~51°,高程分布范围为1302~1606 m,在坡向上阴坡的发生数量多于阳坡,西向和西北向浅层滑坡最为发育;4)流域内的滑坡多属降雨诱发的山体滑坡,确定性模型SINMAP为预测这一类滑坡提供了强大的工具,不仅评估了现有的已发生的滑坡的稳定性,也预测了未来在不同降雨条件下可能发生滑坡的地区。分析结果可为预防和减轻滑坡灾害带来的损失,合理的城市规划和道路选址等提供参考。

The geological environment of the loess hilly region is fragile,and it is easy to induce shallow loess landslides during the rainy season.Zhidan County is a typical loess hilly region,where the loess landslide is widely distributed and the shallow loess landslides account for 85%of the total number of landslides.The research area is located in Zhidan County of Shaanxi Province,where the geological environment condition is poor and shallow landslides account for 80%of the total landslides.Evaluation of shallow landslides stability is not only conductive to understand the occurrence and development of shallow landslide,but also of great significance for disaster prevention and regional planning.In this paper,96 shallow landslides were acquired through field investigation,aerial survey by UAVs and interpretation by satellite image.The basic physical and mechanical parameters were obtained through laboratory experiments.The SINMAP model was used to evaluate the stability of shallow landslide under different rainfall conditions in the study area.Then the area of stability regions,the number of landslide points and landslide density under different rainfall levels were analyzed.The simulation results of SINMAP model show that the overall stability of the study area is relatively high.When the precipitation value is 8.6 mm,15 mm,25 mm,50 mm and 100 mm,the area falling in instable classes(including high instable,instable and potentially instable)accounts for 9.12%,18.93%,23.17%,30.94%and 38.67%of the total area respectively,and the unstable area does not exceed half of the area of the watershed.The landslide density of the high instable class is the largest,followed by the instable and potential instable class.The areas expand in instable classes with the increase of precipitation values,and the areas in high instable classes located in the place with steep slope and intensive fluvial erosion has a small change in area.The stability of shallow landslide depends a great extent on the local topography conditions:the elevation is between 1302~1606 m,the slope is between 20°~51°,and the largest number of shallow landslides is in the westward and northwest slope.Finally,the stability simulation results by SINMAP model is verified through landslide field investigation.SINMAP model provides a powerful tool to predict the stability of rainfall induced shallow loess landslides.It not only evaluates the stability of existing landslide,but also predicts the potential landslide in the future under different rainfall conditions,which will be helpful to prevent and mitigate the loss caused by landslide disaster and provide reference for reasonable urban planning and road siting.