Abstract
This paper summarizes the results of a theoretical and experimental program at Sandia National Laboratories aimed at identifying and modeling key physical features of rocks and rock-like materials at the laboratory scale over a broad range of strain rates. The mathematical development of a constitutive model is discussed and model predictions versus experimental data are given for a suite of laboratory tests. Concurrent pore collapse and cracking at the microscale are seen as competitive micromechanisms that give rise to the well-known macroscale phenomenon of a transition from volumetric compaction to dilatation under quasistatic triaxial compression. For high-rate loading, this competition between pore collapse and microcracking also seems to account for recently identified differences in strain-rate sensitivity between uniaxial-strain “plate slap” data compared to uniaxial-stress Kolsky bar data. A description is given of how this work supports ongoing efforts to develop a predictive capability in simulating deformation and failure of natural geological materials, including those that contain structural features such as joints and other spatial heterogeneities.
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Acknowledgements
The authors gratefully acknowledge the support of the Advanced Simulation and Computing Physics and Engineering Models Program entitled, “Enhancement Geomechanics Modeling,” led by John Pott of Sandia National Laboratories. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-A04-94AL85000.
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Fossum, A.F., Brannon, R.M. On a viscoplastic model for rocks with mechanism-dependent characteristic times. Acta Geotech. 1, 89–106 (2006). https://doi.org/10.1007/s11440-006-0010-z
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DOI: https://doi.org/10.1007/s11440-006-0010-z