[SCG63-P08] Dilatancy of ultra-mafic and mafic rock under triaxial compression test
Keywords:Dilatancy, Peridotite, Mafic rock, Triaxial compression test, Moho discontinuity
Tri-axial compression tests were conducted on cylindrical specimens of mafic granulite and peridotite collected from Horoman. All the experiments were done with Intra-Vessel Deformation and Fluid-Flow Apparatus at constant strain rate (4.2×10-6 s-1), confining pressure (20 MPa) and room temperature. During tests strain measurements were performed with strain gauges stuck on the specimens.
The experimental results showed that the onset of dilatancy of mafic rock ranged from 40 % to 65 % of the maximum differential stress and the volume dilation ranged from 0.6 % to 1.0 %, which are similar to those of granite (e.g. Brace et al, 1966). On the other hand, the onset of dilatancy of peridotite was higher than 75 % and the dilation was less than 0.3 %. Furthermore, it seemed that the onset of dilatancy delays and the volume dilation decreases with increase in Young’s modulus. This relation is considered to be reasonable from the theoretical mechanism of crack behavior in deformed rocks (e.g. Bieniawski, 1967). These differences of dilatant behaviors indicate that the crack distributions and/or geometries are different between crust and mantle and the seismic anomalies can be induced at the Moho.