CRACK GROWTH AND THE THERMOELASTIC BEHAVIOR OF ROCKS

The effect of cracks on the elastic moduli of rocks has received considerable attention in recent years; the role of crack growth in the brittle creep and dilatant deformation of rocks has also been extensively studied. However, less attention has been paid to the effects of cracks on other thermoelastic constants of rocks, such as their thermal expansion coefficients, and to the deformation resulting from the growth of cracks in rocks containing internal stresses. These effects have been studied experimentally and discussed in qualitative terms, but quantitative theories relating thermoelastic behavior to the presence or growth of cracks are lacking. A thermodynamic approach can be used to calculate changes in stress, pore volume, and thermoelastic properties for a sample of brittle rock containing open, growing cracks and subjected to changing temperature, pore pressure, and macroscopic strain. The analysis is based upon the relation between the flow of energy to an advancing crack edge and the crack tip stress intensity factors. The effects of cracks on the theraml expansion of aggregates is illustrated by applying the results of this analysis to a simple model of a monomileralic aggregate of uniaxial grains. -Author