Changes in Discontinuities' Role During Failures with Different Slope Orientation: An Example from Chinarock Area, Koya City, Kurdistan Region, Northern Iraq

Landslides are dangerous, especially in mountainous regions where road construction is prevalent. Identifying rock discontinuity’s role in failure mode provides a sound tool to create stable slopes. This study analyses discontinuities' role in slopes on the road that cuts the southwestern limb of the Khalikan anticline in the Chinarock area, Koya City, Kurdistan Region, Northern Iraq. Three slopes were chosen with different slope directions to illustrate the role of changing slope attitudes on discontinuities and potential failure modes. Data from previous works were consulted, and detailed fieldwork was conducted to measure slope and discontinuity attitudes and classify them into sets. Eventually, kinematic analysis will identify the potential failures and the role of discontinuity. Three types of failures were diagnosed: plane sliding, direct toppling failure and wedge sliding on the Main and Right slopes, while the Left slope shows wedge sliding only. In the Main and Right slopes, the discontinuity set 2 represents Plane sliding and Basal surface, respectively; thus, sets 1 and 3 discontinuities represent Lateral release surface. In contrast, the bedding planes represent Upper-release surfaces on both slopes. Further, the Left slope shows that sets 1 and 2 and sets 2 and 3 discontinuities surfaces represent shared sliding surfaces. The results show how changes in the slope face’s attitude affect the failure mode and how these changes affect the roles of different discontinuities, especially in certain failures. The study emphasizes understanding these relationships to design stable slopes in vulnerable landslide areas.