Slope stability analysis of vulnerable landslide zones along Srinagar Rudraprayag national highway Uttarakhand

Abstract

The failure of rock slopes along the roads in fragile belt of Himalaya is identified as a one of the most frequent natural disaster. Such slope failure cases has been creating problem on the strategic National Highway- 58 (NH-58), Uttarakhand. Kedarnath valley and adjoining areas along the transit of the Mandakini River witnessed the nation s worst natural disaster of flash floods and massive landslides in June, 2013 which has made road cut slopes along the Alaknanda River vulnerable. The present study attempted to characterize vulnerable road cut slopes along NH-58 and geological mapping at a scale of 1:10,000 was conducted along ~ 17 km stretch from Dhari Devi to Rudraprayag, Uttarakhand. In-situ geotechnical investigations included measurement and estimation of various rock parameters such as Uniaxial Compressive Strength (UCS) and Rock Quality Designation (RQD), Kinematic analysis along with different rock mass and slope mass characterization techniques like basic rock mass rating (RMRb), Slope Mass Rating (SMR) with updated parameter and Continuous Slope Mass Rating (CSMR) were implemented for slope stability classification. A total 35 number of 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 shows that 18 slopes are vulnerable with 6 slopes falling under the class III category (partially unstable), 9 slopes are 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 infrastructures projects at stable zones. In order to reduce the impact of mass wasting phenomenon, remedial measures have been suggested. Site specific measures can be very effective, economical and can be adopted with local material and knowhow.