15:30 〜 17:00
[HDS05-P01] Unraveling the role of particle shape on high mobility of rock avalanches: results of ring shear tests on rice particles
Rock avalanches are distinguished from ordinary landslides by their large volume, high velocity, and long-runout characteristics, and usually present significant hazards to human safety and properties. Many studies were conducted to investigate the reasons for the ultra-low shear strength of the sliding mass from rock avalanches, in order to reveal the movement mechanism of rock avalanches. Recently, some field evidence indicated that rock fragmentation can occur throughout the runout. The phenomenon of inverse grading is a typical feature of rock fragmentation. During the transfer process, rocks become particles of various sizes and shapes. It has been inferred that particle shape can affect the shear strength and other mechanical behavior of granular materials. Nevertheless, less evidence had been obtained. In this study, to improve our understanding of the effect of particle shape on shear strength and to reveal the motion mechanism of particles with different shapes, we conducted a series of ring shear tests on rice materials with different shapes. Our results show that rice particles have a significant rate effect (with increasing shear velocity, the shear resistance decrease) during shearing and that the rice with longer grains has a lower shear strength than the short one at high shear velocity. Based on the results of tests on different types of rice shown in this study and other results of our tests on sandy materials, we concluded that the particle shape of the granular materials can greatly affect its friction strength, and inferred that the different shear behavior may result from the different shear mechanisms, such as laminar sliding and turbulent shearing occurring with the shear zones of granular materials.