Strain rate dependence in dolomite inferred from impact and static compression studies

Abstract

Plate impact techniques and laser interferometry instrumentation were used to obtain continuous one-dimensional compression wave data through states of loading and unloading on Blair dolomite in the stress range of 0 to 6.5 GPa. These data are used to infer the dynamic stress--strain response. Both the character of the wave propagation and a comparison with quasi-static uniaxial strain data obtained by other workers suggest substantial strain rate dependence in this rock. The dynamic yield stress of 2.5 GPa determined from the wave propagation data was approximately a factor of 10 higher than that observed in the quasi-static data. Wave propagation below 2.5 GPa is suggestive of viscoelastic response, and a nonlinear Maxwell constitutive equation fitted to these data provides a characteristic relaxation time of 0.01 ..mu..s. Comparison of dynamic and quasi-static loading data suggests that the large difference in observed yield stress could be the result of a transition from failure by brittle fracture to failure by intracrystalline plastic flow.