Slope stability analysis of road cut slopes along NH-58 in Alaknanda Valley from Dhari Devi to Rudraprayag, Uttarakhand, India

Slope stability assessment of vulnerable slopes was conducted along National Highway 58 (NH-58) from Dhari Devi to Rudraprayag (~17 km), Uttarakhand. Kedarnath devastation in June, 2013 due to flash floods has made road cut slopes along the Alaknanda River vulnerable, which has a history of frequent landslides particularly at Kaliasaur (sites K1, K2, K3). At Kaliasaur landslide (site K1), the instability is mainly controlled by the combination of pre-existing tectonic fracturing, plunging fold, structural damage zones formed due to the passage of regional Kaliasaur Fault and at site K3, fault gouge is found due to shearing of quartzite. A total of 35 road cut slopes were investigated along NH-58 and kinematic analysis of joint data shows that 18 slopes are prone to planar failure, 7 for wedge failure and 8 for toppling failure. Slope mass rating (SMR) and continuous SMR show that 18 slopes are vulnerable with 6 slopes falling under the class III category (partially unstable), 9 slopes under class IV (unstable) and the rest of 3 slopes are completely unstable fall under class V causing landslides on NH-58. Maps with location of stable, partially stable, unstable and completely unstable sites are formed to take infrastructure projects at stable zones. Research highlights Kaliasuar fault causes active landslides along NH-58, Uttarakhand. Maps with location of stable sites are provided for infrastructure projects. Instability at Kaliasaur Landslide is caused by plunging fold, pre-existing tectonic fracturing. Conducted kinematic analysis and geo-mechanical classification based on CSMR of 35 slopes in the study area.