INFLUENCE OF HIMALAYAN OROGENY ON GEOTECHNICAL ASSESSMENT

The origin of Indian Himalaya is attributed to striking of Indian and Eurasian plates and therefore the youngest mountain chain has distinctive geological characteristics due to various tectonic, erosional and sedimentation processes. Because of their enormous hydropower potential these mountains are attractive for project development. Infrastructure works for development of railroads and highways are also in progress or in planning stage in these ranges.

Different ranges depending on the age of geological formations offer various challenges. There are issues such as low compressive strength in younger rocks or high to moderate stresses in deep seated tunnels. Problems of dealing with water ingress, crushed rock formations or sheared rock masses epecially in tunnels are also associated with certain geologic conditions such as working near fault zone, below intersections of natural drainages etc. There is strong and direct relationship between the evolution of Himalayas, physio-graphic zones and resultant geological conditions and geotechnical problems experienced in large engineering projects of the Himalaya. Therefore it is necessary that geology of Himalaya is fully understood before planning of large engineering projects in the region. Not only advanced direct geotechnical investigations are necessary but full knowledge of regional geology and geo-tectonics is required before embarking upon a focused site investigation program and locating large structures. Known areas of difficulty should be avoided to save time and cost of investigation as well as problems during construction. Such a work program has yielded best results in the past. The role of pure geological studies in engineering geological or geotechnical assessment should never be forgotten or diluted.