Slope Stability Analysis in Jhika Gali Murree

Abstract

Landslide is a natural phenomenon which involves the failure of slope materials varying from the small insignificant ones to catastrophic movements. The northern region of Pakistan is susceptible to land sliding which in Pakistan is the most expensive geological hazard. Important land routes linking Pakistan and China frequently get disturbed due to land sliding. These trade routes at times remain close for hours, sometimes even days, activities are suspended due to land sliding. Amongst the mountainous region of Pakistan, Murree is considered to be one of the worst slide-affected areas. The landslide hazard in Murree has been a cause of great concern affecting the safety of life and property. During last three decades, the extent and cruelty of the problem has aggravated due to haphazard land use and un-planned urbanization taking place at a large scale. Given this scenario it is evident that landslide vulnerability and studies for the area are of paramount need. Landslides and related slope failure phenomenon occur in all parts of the world particularly in mountainous areas. A wealth of experience and knowledge has been accumulated over years in developing understanding, identification and treatment of landslide hazards, however, due to diverse nature of this problem knowledge in this field is still in disintegrated form. The area requiring meticulous attention is the proper investigation and analysis for practical design and cost-effective remedial measures. This requires a clear understanding of the conditions and processes that cause landslide. Much progress has been made in developing techniques to minimize the impact of landslide through more efficient, quicker and cheaper methods of mitigation. Multiple ways have evolved in mitigating the effect of landslides, generally landslides can be controlled by one or combination of any four principle measures i.e. adjustment of slope geometry, drainage, retaining structures and internal slope reinforcement. Level of effectiveness and acceptability might vary in applying these measures, a particular slide may require an immediate and absolute long-term correction, whereas, another may only require minimal control for a short period. In this study the causes for instigation of landslides in Jhika gali are evaluated and remedial measures are suggested. Field investigation plan was prepared to evaluate soil, rock strata and surface / subsurface drainage. Relevant field tests were performed to determine insitu strength properties of soil / rock. Laboratory testing plan was prepared to determine the strength properties of soil and rock samples in simulated conditions. Computer software Geo Slope, Rocscience Slide & Phase were used for 2D Analysis. For 3D Analysis Clara 3D, Surfer and ArcGIS were used. The analysis of slopes is based on the material properties obtained from tests and survey conducted for each potential landslide, under simulated conditions. The analysis of the slopes has been carried out for different scenarios, controlled by material input parameters. Finally, the slopes have been checked for the effects of the recommended solutions.