Stress distribution during cold compression of a quartz aggregate using synchrotron X-ray diffraction: Observed yielding, damage, and grain crushing
Herein, we report new experimental results that quantify the stress distribution within a quartz aggregate during pore collapse and grain crushing. The samples were probed with synchrotron X-ray diffraction as they were compressed in a multianvil deformation apparatus at room temperature from low pressure (tens of megapascal) to pressures of a few gigapascal. In such a material, stress is likely to concentrate at grain-to-grain contacts and vanish where grains are bounded by open porosity. Therefore, internal stress is likely to vary significantly from point to point in such an aggregate, and hence, it is important to understand both the heterogeneity and anisotropy of such variation with respect to the externally applied stress. In our quartz aggregate (grain size of ~4 μm), the measured diffraction peaks broaden asymmetrically at low pressure (tens of megapascal), suggesting that open pores are still a dominant characteristic of grain boundaries. In contrast, a reference sample of novaculite (a highly dense quartz polycrystal, grain size of ~6–9 μm) showed virtually no peak broadening with increasing pressure. In the quartz aggregate, we observed significant deviation in the pressure-volume curves in the range of P = 400–600 MPa. We suggest that this marks the onset of grain crushing (generally denoted as P* in the rock mechanic literature), which is commonly reported to occur in sandstones at pressures of this order, in general agreement with a Hertzian analysis of fracturing at grain contacts.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States); Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)
- Grant/Contract Number:
- SC0012704; EAR 11-57758; EAR 1361463; EAR 1045629; EAR 1141895; AC02-98CH10886; AC02-06CH11357
- OSTI ID:
- 1409604
- Report Number(s):
- BNL-114656-2017-JA
- Journal Information:
- Journal of Geophysical Research. Solid Earth, Vol. 122, Issue 4; ISSN 2169-9313
- Publisher:
- American Geophysical UnionCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Note: Elastic wave velocity measurement using ultrasonic system with two-reflectors
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journal | August 2018 |
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