Visualization of the Fragmentation of a Weak Granular Material During Compression
The purpose of this research was to visualize the crushing of a weak granular material during compression. In order to be able to see the individual particles of the sample with out the usage of sophisticated and expensive equipment, roasted chick peas were used to model granular material. The chick peas were chosen because of their size and availability. A series of uniaxial confined compression tests were run on the chick peas to check different aspects of the fragmentation. All the samples used in the tests were prepared the same way having the same initial height and mass. The samples also had uniform gradation. An initial test was run on the chick peas to an applied vertical load of 3 kN. This test was used to create a void ratio versus the logarithm of the stress curve. From the curve constructed from the results of the first test four applied vertical loads were chosen. These four applied vertical loads were used throughout the research. The first set of uniaxial confined compression tests were used to determine how many chick peas were broken during compression. The next set of uniaxial confined compression tests were used to run sieve analysis on each sample and to determine how the gradation of the sample changed as the applied vertical load increased. Another confined uniaxial compression test was run to a selected load to determine how the crushing occurred internally. Through out the research several pictures were taken with a digital camera to help illustrate the crushing inside and outside the samples. Pictures outside the samples were possible since the cylinders used for the compression tests were transparent. A fractal analysis was done using the results of the sieve analysis for each sample. Fractal fragmentation dimensions were calculated to determine the degree of crushing at each of the applied vertical loads. Another fractal analysis was done using a Seirpinski Gasket in order visualize the way the samples developed a fractal size distribution. Six level of the gasket were generated and used to model a sample fragmenting during compression.
Advisor:Calixto I. Garcia; Luis E. Vallejo; Jeen-Shang Lin
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Keywords:civil and environmental engineering
Date of Publication:09/25/2007