NUMERICAL MODELLING FOR SNOW AVALANCHE MOTION

Abstract

"An avalanche is a rapid down slope movement of a large mass of snow that may also contain pieces of rocks, soils or ice." In the alpine areas of snow bound western and central Himalayan region in the northern boundary of India, due to snow avalanches a considerable number of human lives are lost and unaccounted property is destroyed every year, besides causing interruption of traffic movements by blocking approach roads and cutting off supply links to remote inhabited areas and defence establishments. The knowledge of snow depths, velocities, mass flow rates, force and run-out distance of likely avalanches are very much useful for the development of avalanche prone areas of snow bound alpine region. The start of an avalanche is the outcome of a contest between the stress and strength within the snow pack on an inclined terrain. On the basis of initiation mechanism and starting-zone failure patterns, snow avalanches are generally classified as loose snow avalanches and slab avalanches. All the available computational models, for predicting the dynamic forces and extreme avalanche run-out distances of snow avalanche, have been developed either with the help of application of avalanche-dynamic equations or using empirical statistical relationships of regression analysis of terrain slope and avalanche profile length. Now a days, the kinematic wave approximation theory is a well-accepted tool for modelling a variety of hydrological processes in the water resources sector. The basic assumption in the kinematic wave approximation theory is that the local acceleration term, the convective acceleration term, and the pressure force term can be neglected, which enables to assume that the energy line or friction slope is parallel to the avalanche xiv path terrain slope. The Kinematic wave approximation theory can be applicable if the dimensionless Kinematic wave number K (= SOL / HFF2 ) is greater than 10. The main objective of. this dissertation work is to investigate the general applicability of kinematic wave approach to the modelling of snow avalanche motion and also investigating the performance of the proposed model with regard to the existing hydrodynamic (PERLA) 'model in terms of predicting the velocity in the avalanche path segment. Based on some assumptions by applying the kinematic wave approximation theory; a numerical model is formulated and analyse the simulation results using different values of segment of avalanche path, initial flow height of avalanche, coefficient of dry ground friction and coefficient of turbulence or dynamic friction. On perusal of the simulation results, it could be concluded that in the initial reach of avalanche path, where terrain slope is higher the kinematic wave number is less and it is higher in the lower reach of avalanche path. Simulation results are also shows that higher values of , lower values of L , higher values of H and lesser values of μ contribute to lowering of kinematic wave number.. Further, the avalanche velocity, as obtained by the proposed model has been compared with the avalanche velocity, as obtained by hydrodynamic (PERLA) model. On perusal of simulation results, it could be discerned that almost all the computed results, by kinematic wave approximation theory, have a close confirmity with those produced by application of hydrodynamic (PERLA) model in the transition zone,