基于斜坡单元的滑坡风险识别——以贵州万山浅层土质斜坡为例

Landslide hazard identification based on slope unit:A case study of shallow soil slope in Wanshan,Guizhou Province

识别斜坡地质灾害风险已成为西南山区地质灾害防治的重要基础工作,通过GIS软件划分出孕灾斜坡单元,选取坡度、坡高、覆盖层厚度、滑体土类型、人类工程活动、日最大降雨量等6项指标作为评价因子,利用层次分析法开展山区大比例尺地质灾害危险性评价,初步评价出研究区危险性斜坡。以万山区1:1万地质灾害风险调查获取的斜坡剖面模型为基础,通过取样、试验,综合选取岩土体物理力学参数,利用有限元软件对暴雨状态下的高危险斜坡进行数值模拟,通过强度折减计算出安全系数均小于1.05,并存在不同程度的塑性贯通区。其分析结果与层次分析法评价结果一致,可作为西南山区浅层土质滑坡隐患识别的定量化评价方法。

The identification of slope geological disaster risk has become an important basic work for geological disaster prevention and control in southwest mountainous areas.The potential unstable slope units are divided by GIS program,and six factors including dip angle,elevation,thickness of covering,slope soil type、human engineering activities and maximum rainfall were selected as evaluation factors.Analytic hierarchy process(AHP)is carried out to assess risk of large-scale geological hazards in mountainous areas and preliminarily evaluate the unstable slopes in the study area.While taking slope models in study area of Wanshan as examples,the safety factors under heavy rain condition are analyzed with FEM approaches.In this method,we only reduce the strength parameters of elements whose shear strain is beyond the limit value.The reduction process will continue until the global slope failure associated with the formation of whole sliding surface whose limit shear strains beyond the limit value.It is found that all of the safety factors in 12 slopes are below 1.05 which accorded with the results of AHP.It is proved that proposed method can be seen as a quantitative evaluation method for geological hazard identification of the soil unstable slope in southwest mountainous area.