Distribution Difference of Landslide and Collapse in the Loess Tableland Area at the Downstream of Jing River

In recent years, the loess landslide and collapse have occurred frequently in the loess tableland area at the downstream of Jing River. These geological hazards threaten the safety, normal order of production and living of local residents. The field investigation has discovered that these geohazards have the distribution characteristic of "East landslide, West collapse", which have close spatial correlation with the secondary geomorphic unit in this area. Previous studies have shown that the agricultural irrigation causes the changes of hydrogeological conditions in the eastern slope belt of this study area, which is the main reason for the loess landslide. But, different types of geological hazards were occurred in the western slop belt of the irrigated area. Therefore, the hydrogeological models have been established to analyze the difference of hydrogeological conditions of different secondary geomorphic units under long-term irrigation. And then, based on the CSD and RTC stress path test, two failure models of slopes under the coupling effect of landform, agricultural irrigation and engineering excavation have been discussed in this paper. The results show that the long-term agricultural irrigation causes a significant increased groundwater level, increased hydraulic gradient, enhanced erosion and changed hydrogeological conditions, which provide favorable formative environment for the formation of loess landslide and become the main cause of loess landslide. In addition, the hydrogeological condition is not strongly affected by irrigation and not easy to induce landslide in the gully area of loess tableland. However, the frequent excavation makes the slope steep and destroys the slope structure, which is the main cause for the frequent occurrence of loess collapse.