Mechanical and transport properties of rocks at high temperatures and pressures. Task III. Technical progress report Number 3, 1 March 1982-30 October 1982
In an effort to characterize the rheology and flow processes (mechanisms of deformation) operative for presupposed semi-brittle behavioral conditions we have conducted a series of drained constant stress creep tests on 2 x 4 cm specimens of dry and water-saturated (Pp = 100 MPa) Westerly Granite at 100 MPa effective confining pressure and temperatures of 300/sup 0/C to in excess of Tm (1000/sup 0/C). The deformation is multimechanistic; microfracturing of apparent extensile and shear origin, glide in quartz and biotite, microfracture healing, dissolution, and mineral alteration are mechanisms observed and evaluated as functions of temperature and strain. We attempt to partition the bulk specimen deformation into that contributed by the individual mineral species in the analysis. Available equations of flow and time to failure are used as response models to characterize the experimental data even though the multimechanistic deformation described above and the quasi-steady state are not compatible with the assumptions underlying the corresponding theories. Data for 600/sup 0/C and below (the brittle field) are well fit by an equation of the form: t/sub failure/ = t/sub 0/ p/sub - ..cap alpha../exp (E/RT -Ksigma), which has been shown to predict the static fatigue time for rock. Using this expression, we calculate apparent activation energies for the total fatigue processes in the ..cap alpha..-quartz field of 7.5 kcal/mole (300 to 400/sup 0/C, dry) and 21.6 kcal/mole (400 to 600/sup 0/C, wet, Pp of 100 MPa. Quasi-steady state flow is observed in the ..beta..-quartz field (700 to 800/sup 0/C) and the flow behavior is described by e = A exp (-Q/RT)sigma/sup n/, where Q = 68 kcal/mole, n = 2.7, and A = 25.2.
- Research Organization:
- Texas A and M Univ., College Station (USA). Center for Tectonophysics
- DOE Contract Number:
- AS05-79ER10361
- OSTI ID:
- 6372794
- Report Number(s):
- DOE/ER/10361-T1; ON: DE83007278
- Country of Publication:
- United States
- Language:
- English
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