MECHANISM OF ROCKFALL WITH ANTI-DIP AND TOP HARD-BOTTOM SOFT ROCK BY UNDERGROUND MININGA CASE STUDY OF ROCKFALL IN KAIYANG PHOSPHORITE, GUIZHOU

This paper takes Kaiyang phosphorite rockfall in Guizhou for example. It analyzes the geological conditions,mining exploitation and failure characteristics. It then develops the process of rockfall deformation with anti-dip and top hard-bottom soft rock. The formation mechanism of this type rockfall is studied through numerical simulation and physical simulation. The results show that this rockfall is induced by specific geological background,dynamic conditions and predisposing factors. Especially,there is a long development process from occurrence to destroy. A rapid destruction form is presented finally. They are specifically deformation of the roof and floor rock in the mine area,appearance of cracks on the top of slope and development of cracks along the steep joints in the slope. There are three failure modes: crack-toppling,crack-slide and crack-shear. Therefore,the key about monitoring and prevention of geological disasters to this type rockfall is precursory information for enhancing early identification and warning.