Slope Stability Analysis and Hazards Assessment of Swat Motorway, Khyber Pakhtunkhwa, Pakistan

Analysis of Slope Stability of Swat Motorway Pakistan

Abstract

The 81-kilometer-long Swat motorway starts from the Karnal Sher Khan interchange connecting M1 motorway with Chakdara, Swat. Major part of the motorway runs through Peshawar basin, while crossing Malakand ranges at some locations. Geologically, this region belongs to weak meta morphosed rocks of Mesozoic age and consists of schist, phyllite and schistose marble. These rocks are excavated for the highway with a height ranges from a few meters to 80 meters, which requires significant stabilization measures.In this case study, slope stability of the benches along the highway have been analyzed by kinematic approach using DIPS (Rocscience software). By using the discontinuities data collected from scanline survey of the area, probability of different modes of failures are predicted and potential unstable zones are determined. Keeping in view the financial aspects, it is desired to have a hybrid stabilization technique in contrast to conventional techniques to make the slopes stable and ensure road safety. Different slope angles are analyzed and it is found that there is high chances of planar failure i.e. 43% (average)1:0.15 sloping grade, while the failure chances can be reduced to 23%, if the slope gradeis kept as 1:0.5 (63.430), which is safer enough.Moreover, the benches are highly unstable under any seismic activity.According to kinematic analysis, a data of 225 discontinuities are recorded which is divided into three sets, among them set 3 is recorded as the most critical set of discontinuities resulting in 68.7 % chances of planar failure. A hybrid stabilization system comprised of a ditch filled with sand or fine debris material and rock fall protection system is proposed, which is economical and easily constructible for slope stability at KM 37 of the Swat motorway. Keeping in view the significance and efficiency of the system, it is recommended to be adopted at other sections of the Swat motorway as well.