SLOPE STABILITY STUDY OF MURREE MUZAFFARBAD ROAD

Abstract

Mountainous landscape is generally prone to landslide hazards; historically landslides have caused extensive damage to human life and infrastructure worldwide. The causes of the landslides can be attributed both to nature and human activity. Historically civil engineering community has faced the challenges of landslide mitigation in mountainous regions. The study in hand is a step towards combating this disaster. Ever since the establishment of the Murree Town in 19th century, the population of the Murree has increased significantly. This has resulted in extension of services, infrastructure, buildings and widening of roads in the area. All this development is being carried out without giving due consideration to engineering and environmental aspects of uncontrolled development on the area. Moreover due to fragile geological formation, absence of proper drainage/sewerage system and uncontrolled deforestation the landslide hazard has further aggravated. To analyze the causes of the landslides in the Galiat Area of Murree, a 20 km section of the road has been selected on the Murree-Muzzafarabad Road. The section starts from Murree Town and terminates at Phagwari Village. The slopes along the route are generally stable where the grades are gentle, vegetative growth is thick and surface/subsurface drainage is controlled. Whereas, the slopes are generally found to be unstable where the grades are steep, vegetative growth is sparse and surface/subsurface drainage provisions are poor. Extensive survey along the road was carried out and based on topography, geology, drainage and vegetative cover the 25 km section was divided into four zones. Two locations with adverse stability conditions were selected for detailed geotechnical investigations. Field investigation plan was devised to explore surface/subsurface soil/rock strata, surface/subsurface drainage and vegetation. Relevant field tests were carried out to find in-situ strength and physical characteristics of the soil/rock. A detailed laboratory-testing plan was formulated to study the behavior of the soil and rock samples in simulated conditions (covering normal to worst case scenario). Using the field survey data and field and laboratory evaluated material parameters, the slopes were modeled and analyzed using computer software (GEO-SLOPE Office). The analyses were performed for both stable and critical conditions. The modeling of the slopes was carried out for different scenarios, controlled by the material input parameters. For the slopes to be stable along the route (Murree-Phagwari), during construction phase of the road/infrastructure executing agency must take into account stability measures such as proper blasting techniques, proper slope formation, benching and drainage etc. The local residents must be educated about the land use and its environmental effects. Land surface/subsurface drainage needs to be studied in detail and planned accordingly. Stabilization measures, such as erosion control, properly designed hydrological structures, retaining structures and expedient techniques have been evaluated and proposed. The slopes were checked for the effects of the recommended solutions.