The dissertation details work aimed toward the development and implementation
of a 3-D impact fragmentation module to perform rock fall analysis by taking into
account impact fragmentation. This fragmentation module is based on a database of a
large set of impact simulations using a fully calibrated discrete element model (DEM),
and is employed to predict impact fragmentation processes in rockfall analysis by either
training a neural network model or linearly interpolating the database.
A DEM was employed to model impact fragmentation in the study. A DEM code
was developed from scratch. The model was first calibrated and verified with
experimental results to demonstrate the capability of modeling both quasi-static and
dynamic material behavior. Algorithms to calibrate the model’s micro-parameters against
triaxial tests on rocks were presented. Sensitivity analyses were used to identify the
deformability micro-parameters by obtaining relationships between microscopic and
macroscopic deformability properties. The strength model parameters were identified by
a global optimization process aimed at minimizing the difference between computed and experimental failure envelopes. When applied to the experimental results of tested
granite, this calibration process produced a good agreement between simulated and
experimental results for both deformability and strength properties.
Dynamic compression and SHPB tests were performed to verify the dynamic
model. A strain-rate-dependent dynamic strength was observed in the experimental
results. This strain-rate-dependent dynamic strength was also confirmed by the numerical
results. No rate-dependent constitutive model was used in the DEM to simulate dynamic
behavior. This simulated rate-dependent dynamic strength can be attributed to material
inertia because the inertia inhibits crack growth.
Some fundamental mechanisms of impact fragmentation associated with rockfalls
were then numerically investigated. The developed DEM code was coupled with a
simplified impact model inspired by the theory of dynamic foundations. It has been
shown that the magnitude of impact velocity, the angle of the incidence, the ground
condition all play very important roles in impact fragmentation.
Several case studies were performed to validate the developed impact
fragmentation module in rock fall analysis. It has been demonstrated that the developed
fragmentation module can reasonably predict impact fragmentation and perform some risk analysis in rock fall analysis. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/6591 |
| Date | 21 October 2009 |
| Creators | Wang, Yuannian |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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