GREAT LANDSLIDES IN HIMALAYA MOUNTAIN AREA AND THEIR OCCURRENCE WITH LITHOLOGY

The Himalayan region,locating in the south of Qinghai-Tibet Plateau,is characterized with the fastest uplifting and actively dynamic motion.This area is one of the worst landslides hit areas in China.The serious landslide disasters have brought great harm to the national economic and social development.With the aid of imagery interpretation and field investigation,the paper studies the distribution of the serious landslide disaster and its relationship with lithology,and divides the lithology in the region into 13 engineering geology rock groups as follows: loose rock group,soft rock group,soft rock mixed with secondary soft rock group,soft rock mixed with secondary hard rock group,secondary soft rock group,secondary soft rock mixed with soft rock,secondary soft rock mixed with secondary hard rock group,secondary soft rock mixed with hard rock group,double-layer with secondary hard rock and secondary soft rock group,secondary hard rock mixed with soft rock group,secondary hard rock mixed with secondary soft rock group,secondary hard rock group,hard rock group.Then the paper concludes that the great landslides prompt to occur in the soft rock group,secondary hard rock mixed with secondary soft rock group and hard rock group; however there is few great landslides occurred in the soft rock mixed with secondary soft rock group,secondary soft rock mixed with secondary hard rock group.The distribution characteristics of the great landslides have indicated the complicated relationship between the formation lithology and occurrence of the great landslides: on the one hand,the soft rock area is too weak to slide,on the other hand,the steep and high area dominated with hard rock often tend to slide.