5. Geotechnical Investigation of Toldi Landslide Along the National Highway-44 (NH-44), Udhampur, J&K

The Toldi slide falling in the Samroli area along the NH-44 in the Udhampur district of Jammu and Kashmir has been plagued by frequent failures during insistent rainfall from last more than three years. This slide falls within the Murree Group of rocks comprising interbedded medium- to fine-grained sandstone and mudstone which is considered as the water-sensitive lithology. The current slide on the basis of its areal content is categorized as a medium slide and covers an area of about 51,888 m². It is also categorized as a rock slide depending on the kind of movement and the geologic material. The fundamental goal of the present study was to comprehensively understand the underlying failure mechanisms, with the aim of proposing immediate remedial measures to mitigate the losses and disruptions experienced by the population. In order to determine the quality of the rock mass and the slope mass's instability, the current study includes extensive field investigations as well as geotechnical studies in the form of rock mechanics (RMR, SMR and kinematic analysis). The basic rock mass rating inferred that the rock mass falls under fair category; however, the slope mass rating indicated a completely unstable slope with a high likelihood of failure (failure probability of 0.9). Kinematic analysis on the other hand uncovered two prevalent modes of failure at the site: planar and wedge failures. The study also inferred that the unsystematic toe cutting of the water-sensitive lithology is the dominant reason behind this landslide. Other causes include uncontrolled blasting, mechanical excavation, subsequent rainfall, improper drainage, steeper slope angle and shear zones around the slide.