Elastic moduli, thermal expansion, and inferred permeability of two granites to 350{sup 0}C and 55 Megapascals
Journal Article
·
· Journal of Geophysical Research
OSTI ID:59267
The coefficient of thermal linear expansion {alpha}, Young`s modulus E, and bulk modulus K have been determined for the Westerly and Stripa granites to temperatures T of 350 {sup 0}C and pressures P to 55 MPa. Using conventional triaxial aparatus, displacement measurements were made on three samples from each of three orthogonal directions for both rocks. Comparison of the directional values at any P, T, and those from the nine-sample population indicated that within our precision, both granites are isotropic in E, K and {alpha}. Both E and K for both rocks decreased with T and increased with P in a nonlinear fashion. From 19{sup 0} to 350 {sup 0}C, E decreased by as much as a factor of 2 and K decreased by 2 to 3 times, depending on P. From 6 to 55 MPa, E increased by factors of 3 to 6 and K increased by 3 to 5, depending on T. Values for {alpha} were neither constant nor a monotonic function of P or T. In both granites over the P range investigated, {alpha} typically increased from 6 to 12 x 10{sup -6} {sup 0}C{sup -1} at 40 {sup 0}C to 10--15 x 10{sup -6} {sup 0}C{sup -1} at 325 {sup 0}C. In both rocks over the T range investigated, increasing P from 6 to 55 MPa generally decreased {alpha} by 1--5 x 10{sup -6} {sup 0}C{sup -1}. Most measurements are consistent with microcracks controlling the thermoelastic response by cracks opening with increasing T and closing with increasing P. Changes in crack porosity phi due to bulk compressibilit y and thermal expansion have been calculated for both granites. Because K and {alpha}were nonlinear with P and T, phi was inferred to be a complex function of both.
- Research Organization:
- Geosciences Division, Lawrence Livermore National Laboratory, Livermore, California 94550
- OSTI ID:
- 59267
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: B11 Vol. 87; ISSN JGREA2; ISSN 0022-1406
- Country of Publication:
- United States
- Language:
- English
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