Some Mechanical Problems On Granular Medium

We mainly studied three aspects:the experiment of the stone embankment and simulation research, numerical simulation of "Brazil nut effect" and numerical simulation of the internal friction behavior of a rod in particles.From the experiment and simulation study of the stone embankment, through the quasi two-dimensional experiment we found the distribution of the pressure that the pile of stone roadbed acted on the bottom of the road was not uniform, and the pressure of the central location of the stone embankment was less than that of other places; from the experiment we also found the change of foundation’s stress during the collapse of the stone embankment. Based on a two-dimensional discrete element simulation, the distribution of internal force chain of the rockfill was founded, and the reason why the phenomenon happened was also founded. Moreover, the arch effect in the process of collapse was analyzed. We discussed the experimental and simulation results, and analyzed the reason of their differences. Furthermore, we found out the mode of embankment’s collapse in frozen region.In the numerical simulation of "Brazil nut effect", the result that the two kinds of particles’ separation speed increased with the growth of gravity under the certain condition was founded, and the dependence of the separation velocity on the acceleration of gravity was the linear relationship, what’s more, the simulation results and the experimental results were agreeable qualitatively. Besides, we studied how the particles’friction coefficient effected on separation speed, and found a "bottleneck value" of the coefficient of friction:when the coefficient of friction is less than this value, the separation speed will be affected by the friction coefficient very much; when it is greater than this value, the separation speed will be affected by the friction coefficient very small.In the study of numerical simulation of the internal friction behavior of a rod in particles, we found the relation between the sliding friction of the rod and the height of particles; in the study of resistant-drawn force of a rod imbedded in particles, the relationship between resistant-drawn force of rod, rod’s diameter and height of particles was founded, and it qualitatively coincided with the original experiment and theory. The simulation results confirmed the rationality of Janssen Model indirectly.