 |
| Titel |
Investigations on comminution of sheared prismatic granular materials using the discrete element method |
| VerfasserIn |
D. Weatherley, B. Wruck, W. Hancock, G. P. Chitombo |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066096
|
|
|
|
|
|
| Zusammenfassung |
| The comminution (or breakage) of granular materials under shearing loads is conjectured to
strongly influence dynamics of both natural processes (such as fault zone evolution and
landslides) and man-made processes (such as underground cave mining and minerals
processing). Previous laboratory [1] and numerical studies [4] have demonstrated that two
distinct breakage mechanisms contribute to the comminution of granular materials under
shear. The first mechanism is that of abrasion in which grinding or chipping removes small
volumes of material from the surface of larger blocks. The amount of abrasion has been found
to be dependent both on the total shear strain and the confining pressure applied to the
granular material. The second breakage mechanism is that of bulk-splitting, in which a single
block is broken into two or more smaller blocks. The degree of bulk-splitting has been shown
to be largely dependent upon confining pressure, and only to a lesser extent the total shear
strain.
Common to previous laboratory and numerical studies is that the granular material is
typically initially mono-disperse and often of a contrived shape (cylindrical [1] or
spherical [4]). This approach has two adverse consequences. Firstly, the initial granular
material has a porosity much higher than a similar volume of compacted prismatic
material. The higher porosity results in less dilation of the granular material as shear
commences, which may inhibit breakage via builk-splitting. Secondly, there are fewer
edges or corners, the sites most amenable for abrasion both during confinement and
shear.
This study extends previous studies using the Discrete Element Method (DEMÂ [2]) to
investigate the breakge mechanisms of sheared prismatic granular materials whose initial
porosity is near zero. The granular prismatic material is constructed by first filling a
volume with large spheres of variable size. These spheres are then replaced by convex
polyhedra forming planar surfaces between adjacent spheres. Finally, the convex
polyhedra are filled with bonded spherical particles to simulate the brittle-elastic
response of the granular material.As in previous studies, the granular assembly is
then compressed to various confining pressures and sheared to large total shear
strains.
During these so-called annular shear-cell experiments, each breakage event is analysed to
determine whether it qualifies as an abrasion event or bulk-splitting event. The
size-distribution of fragments within the shear-cell is also monitored throughout the
experiments. Preliminary results confirm the qualitative relationships between applied loads
and breakage mechanisms described above. Quantitative comparisons with previous DEM
studies will be presented at the meeting.
These experiments were conducted using ESyS-Particle, an Open Source DEM
simulation package for multi-core PCs or supercomputers [3].
References
[1]Â Â Â Bridgwater, J. and Utsumi, R. and Zhang, Z. and Tuladhar, T. (2003), Particle
attrition due to shearing – the effects of stress, strain and particle shape, Chemical
Engineering Science, 58, 4649–4665.
[2]Â Â Â Cundall, P.A, and Strack, O.D.L (1979), A discrete numerical model for
granular assemblies, Geotechnique, 29, No. 1, 47–65.
[3]Â Â Â ESyS-Particle High-Performance Discrete Element Simulation Software,
https://launchpad.net/esys-particle
[4]Â Â Â Mair, K. and Abe, S. (2011), Breaking up: comminution mechanisms in
sheared simulated fault gouge, Pure Appl. Geophys., 168, no. 12, 2277–2288. |
|
|
|
|
|
|