Mitigation Measures for Landslide Protection along a Highway in the Himalayan Region

Abstract

The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rock-falls, deep-seated slope failures, mudflows, and debris flows. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable. Identifying and suggesting a remedial measure to landslide involves sifting through a maze of complex probabilities and an understanding of the micro and macro parameters causing the landslide. There is always a dichotomy between qualifying and quantifying a landslide situation and it vacillates between art and science, philosophy and statistical analysis and investigational approach and heuristic analysis. The landslide analysis cannot follow a fixed template and is dependent upon a number of local factors. In the present study, landslide sites were selected along NH 94 covering the stretch from Rishikesh to Uttarkashi. During the first visit carried out in December 2020, a need was felt to formalize and standardize a data collection sheet which is more in tune with the current area of study and covers all the aspects pertinent to the region. In the subsequent visits, the format was further improvised as it was found that the factors contributing to a landslide were site specific. In some situations, it is the technical parameters which enable the decision making processes while in others, it is the decision making processes which take a lead in deciding the mitigation options. The present study provides link between the fundamental geotechnical parameters responsible for stability/instability of a slope and the factors influencing these fundamental characteristics.