LAUSR

The engineered slopes along transportation routes in the Himalayan region are manifested by multiple sets of discontinuities and are vulnerable to structurally controlled failures. The hazard potential along one such route was assessed by an empirical Q-slope method. The investigated engineered slopes along the route are unstable, and the Q-slope value ranges from 0.0023 to 0.7701. By considering the ongoing road development and excavation works, optimal angles without any requirements of reinforcement measures ( β ) were determined for the probability of failure (PoF) as 1%, 15%, 30%, and 50%. The outcomes obtained by Q-slope were also correlated with the continuous slope mass rating (CSMR) values. A linear relationship was obtained between Q-slope and CSMR values, having the coefficient of determination as 0.67. The study also aims to assess the applicability of the existing Q-slope method for toppling mode of failure. A modified Q-slope method for toppling failure is proposed by considering the basic principles of toppling failure. The role of joint roughness parameter in topple mechanism is highlighted. Consequently, chart based modifications along with proper guidelines for the newly introduced parameter has also been proposed. It is also pointed out that the Q-slope chart is slightly conservative in nature particularly for β corresponding to low Q-slope values. The optimal slope angle for the PoF 1% was correlated with the slope angle at factor of safety as 2, and an extended stable zone is proposed with further scope of development. The modifications and suggestions for the refinement of the system will enhance the applicability of the method for a much broader range of initial ground conditions. The outcomes may be advantageous for the progressing road widening and development work along a section of the transportation route in Uttarakhand Himalaya.