Evaluation of Slope Stability and Application of Rock Mass Classification on the Alagaba New Road, Northeast Sudan.

Abstract

TThe Alagaba New Road, a crucial highway in northeast Sudan, connects the capital, Khartoum, with major Red Sea ports. Part of the road (~ 6 km) has been constructed on hilly terrain with cut and rugged topography. This study aims to characterize the rock mass and assess the stability of jointed rock slopes in seven sites along this dangerous part of the road. To achieve this aim, a comprehensive study was conducted involving the collection of 710 discontinuity readings and representative samples for laboratory testing. The scanline technique and a Brunton compass were employed for field data acquisition. The rock mass rating (RMR), slope mass rating (SMR), and geological strength index (GSI) were then calculated for the target locations. The study area comprises metavolcanic rocks and dolerite dykes in the east, metasediment rocks with less abundant metavolcanic and granodiorite in the west. The eastern rocks have higher Rock Mass Rating (RMR) values (70-77) compared to the western rocks (56-68), indicating better quality due to less weathering. Slope Mass Rating (SMR) results indicate that the eastern sites are more stable than western sites. Kinematic analysis reveals higher planar and wedge failure rates in the western sites, attributed to internal rock variations and external factors like unplanned road cutting and seismicity. The geological and engineering conditions on the eastern side offer the highest assurance of road stability and long-term sustainability. So, it is recommended that the mountain road be constructed on the eastern slope, incorporating benches and terraces to enhance stability.