1:45 PM - 2:00 PM
[SCG74-13] Kinetics study on stress drop and recurrence interval during stick-slip with dehydration
In this study, we analyzed using the data of triaxial compression test made at Sasaki et al. (2016). In the experiment, simulated gouge sample of gypsum hemihydrate, bassanite, between precut gabbro pistons was deformed in high pressure gas medium apparatus at confining pressures of 10 - 200 MPa and temperatures up to 180 ℃. At 200 MPa, 70 ℃ corresponding to non-dehydration condition, samples exhibited stick-slip behavior and the strength of the samples became larger. On the other hand, at 200 MPa, 110 ℃ and higher, likely corresponding to condition for stable anhydrite phase, stick-slip behavior was found to be diminished with the reduction in mechanical strengths with strain.
In this study, we calculate recurrence interval and shear stress drop from data of deformation experiment. We found that recurrence interval and shear stress drop is proportional to confining pressure in experiments with non-dehydration reaction. On the other hand, both recurrence interval and shear stress drop decrease with time despite in an experiment with dehydration reaction. Because the experiment is conducted under constant confining pressure, we consider the decreases in the effective pressure by increasing pore-fluid pressure. From this knowledge, we estimated pore-fluid pressure at time with the effective pressure law. Also, we fit pore-fluid pressure data with Avrami equation. As a result, we found that the evolution of pore-fluid pressure can be described using Avrami equation. From this fact, we consider that by applying the same kinetic approach to different minerals as in this study, it is possible to evaluate the difference of the mechanical properties caused by the dehydration reaction