الملخص

The study area is represented by the slopes, which are found along the Bazian – Chami Rezan road in the Sulaimaniyah Governorate, northeastern Iraq. The slopes were exposed to rock failure mostly rock toppling that led sometimes to the closure of the road. The present study aims to conduct a detailed study of three sites of failure(stations) to be representative of the type of failure (secondary rock toppling) prevailing over the study area to determine the factors affecting the failure. The rock blocks located in the face of the slope that surrounded by discontinuities are stable in the area according to the rules of the rock toppling. The toppling occurs due to the intervention of other factors such as weathering and erosion which led to the remove of the supporting parts at the slope toe in addition to erosion and dissolution of the lower parts of the limestone until the exit of centers of gravity vector outside the base of rock mass. Thus, secondary rock toppling occurs either because of the undercutting such as in the station (1) or because of the weathering and erosion of the basal parts of the same limestone blocks such as in the stations (2 and 3).