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Acoustic velocities in heated block of granite subjected to uniaxial stress
Author(s) -
King M. S.,
Paulsson B. N. P.
Publication year - 1981
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl008i007p00699
Subject(s) - stress (linguistics) , anisotropy , materials science , block (permutation group theory) , atmospheric temperature range , mineralogy , geology , composite material , perpendicular , thermal expansion , optics , geometry , thermodynamics , philosophy , linguistics , physics , mathematics
Acoustic velocities have been measured within a 38 cm cubic block of granite isolated from the surrounding rock. The block was subjected to uniaxial stresses in the range 0‐24 Mpa and to heating in the range 14° to 98°C. An increase in temperature from 14° to 72°C in the unstressed block resulted in an increase in velocities in directions parallel and perpendicular to the applied stress. A further increase in temperature to 98°C in the unstressed block resulted in a decrease in velocities. Application of uniaxial stress with the block at a temperature of 98°C resulted first in uniform increases in velocity to an applied stress of MPa and then sharp decreases from 10 to 14 MPa, followed by uniform increases in velocity to a maximum stress of 24 MPa. A reduction in temperature to 16°C resulted in a sharp reduction in velocity, 25 percent less than originally measured at ambient temperature. It is concluded that, at temperatures rising to 72°C, anisotropic thermal expansion of the crystals comprising the granite causes the closure of microcracks present in the unheated rock. Between 72° and 98°C, particularly when stress was applied, irreversible mechanical changes occurred in the block.