Testing Study On Particle Breakage Mechanism Of Granular Soil

Currently, the research on particle crushing is mainly concentrated in the static and dynamic mechanical properties of soils in the low stress level, but less in the high stress levels. With the dams, tunnels and other projects expanding the scale, the research of soil particles under high pressure crushing has gradually been paid attention. According to the confined compression tests and the grain size analysis tests under the high pressure, two kinds of granular materials of soil particles compression mechanism is discussed, and the combination of fractal theory, image analysis by means of a detailed analysis of particle breakage. The research content and the main results are as follow:(1) To introduce the confined compression test and the grain size analysis test. (size of particles larger than 0.074mm were analyzed by sieving; less than 0.074mm particles were analyzed by laser particle size analyzer)(2) To analyze the compression deformation of granular soils under the high pressure. The results show that the compression and rebound curve consistent with bilinear compression model.(3) Five different methods(B15,B60,B10,Hardin's and Einav's relative breakages) are used to measure the particle breakages, it indicates the relationship between the particle size distribution, the pressure levels, the particle intensity and the breakages. With the increase of load level, fragmentation makes the particle size distribution towards a more favorable direction. In this paper, focus on the breakage situation of the small particle size less than 0.074mm of the broken soil samples, combined with Hardin's relative breakage, set the limit broken particle size to 0.36μm to explore the mechanism of fragmentation of smaller particles further. Set the highest level of load 204.8MPa as the ultimate distribution of particle breakage, according to Einav's relative breakage, the characteristic curves are acquired similar to Hardin's. At that time, the relationship between the soil ratio and the breakage is also analyzed.(4) Using the fractal theory to describe particle crushing, it is found that the original particle size distribution samples have a fractal low in grades, which explains the law of nature fractal widespread. There is a close relationship between the fractal dimension of breakage D and the relative breakage Br·A linear regression revealed a linear relationship between the two quite significant; the correlation coefficient is between the ranges from 0.9466 to 0.9901. It indicates that the fractal dimension D as a quantitative measure of particle breakage index is reasonable.(5) The image analysis on the shape of particle breakage before and after the compression has been down, according to the particle roundness, the surface fractal dimensions and other parameters. It provides a good means to explain the mechanism of particle breakages.Finally, this article summarizes the research results, and makes a prospect on particle breakage research.