GEOTECHNICAL EVALUATION OF DEBRIS FAILURE FROM CHAMOLI TO JOSH IMATH, GARHWAL HIMALYA, INDIA

Abstract

Debris slides are the geological phenomenon in which water saturated ground moves along the slope under the influence of gravity. It is very common phenomenon in Garhwal Himalayan Region. It causes the blockage of roads and water streams. It is the major cause for changing the geomorphology of the Himalaya. If we move along the road in Garhwal Himalayan region then we can see that the some slopes are stable and adjacent slopes are unstable. There are several causes (like vegetation variation, climate change, etc) behind this stability variation. The characterisation of stable and unstable soil slopes on the basis of different soil properties has not been looked into. Hence, the characterisation of stable and unstable soil slopes in terms of the geotechnical properties of soil material is attempted in the present study. Several tests have been carried out in the laboratory for soil samples collected from different stable and unstable slopes in Garhwal Himalayan region. These tests include: (I) Specific gravity determination for grain size distribution of fraction finer than 0.075mm, (2) Sieve analysis for the grain size distribution of fraction coarser than 0.075mm, (3) Soil classification to decide, which kind of shear box will be required i.e., smaller or larger shear box and (4) compaction test (as it is required because the samples collected from the field are disturbed hence we do not know the field density) to determine maximum dry density. The study implies that samples collected from the stable slope have higher value of cohesion and lower value of angle of internal friction. The samples collected from the unstable slopes have lower value of cohesion and higher value of angle of internal friction. So on the basis of cohesion and angle of internal friction we can differentiate and evaluate the stable and unstable soil slopes.