REVIEW ON FRAGMENTATION-RELATED DYNAMICS OF ROCK AVALANCHES

Rock avalanches are characterized by huge volume,high velocity and long runout and greatly threaten human lives and construction of major projects of the mountain areas in China. Fragmentation of rock avalanches is a universal and critical phenomenon,which is one of the prerequisites for the formation of the special internal structures in deposit and even considered as the possible mechanism for the hypermobility of rock avalanches. The fragmentation of rock avalanches has become a highlighted scientific issue in the field of landslide dynamics,since is currently great controversy as whether fragmentation promotes or hinders the mobility of failure mass. The substantial point of this controversy is how the fragmentation process contributes to the runout of the sliding mass when fragmentation itself consuming energy. This article reviews studies on sedimentological characteristics induced by fragmentation process in rock avalanches,including inverse grading,jigsaw structure,retaining of source stratigraphy and local shear band. The implication of fragmentation related deposit characteristics for rock avalanche dynamics is conducted based on those studies. The research progress of the influencing factors of fragmentation process and the friction-weaken mechanisms of rock fragmentation are further discussed. Finally,the controversial issue of energy consumption/friction-weaken induced by fragmentation process is summarized. Then we propose some key issues for future research on the mechanism of fragmentation in rock avalanches.