Stress-strain behavior of a granodiorite and two graywackes on compression to 20 kilobars

Abstract

The complete stress‐strain equation of state for a granodiorite and two graywacke sandstones has been determined on loading to 20 kb axial stress at room temperature. Data under conditions of hydrostatic, uniaxial stress at various confining pressures and uniaxial strain loading are synthesized to define the behavior of these rocks. For the granodiorite it is observed that the onset of dilatancy as well as intersection of the failure envelope is independent of loading path. No dilatant behavior is observed on uniaxial strain loading to 12 kb axial stress. Both sandstones are observed to load below the hydrostat (increased compressibility) in either uniaxial stress or uniaxial strain loading. This enhanced compaction at relatively low pressures is believed to result from the influence of the additional shear stresses, which facilitate intergranular movements in these porous rocks. Dilatant behavior greatly diminishes at higher mean stresses where the rock undergoes a transition in failure mechanism from throughgoing narrow tensile and shear fractures (predominantly intergranular) to pervasive small‐scale fracturing (predominantly intragranular). Dilatancy again becomes important at the highest stresses, where most of the initial porosity has been removed. The data on both rocks are used to delimit areas of characteristic behavior that are uniquely defined in stress space, independent of loading path.

Numerical Modeling of Shock-Induced Damage for Granite under Dynamic Loading

“…Pressure coefficient stress/pressure, P, as a function of the volumetric strain ȝ during uniaxial strain loading for Westerly granite [6] and for Climax stock granodiorite [7]. Pressure constants K 1, K 2 , K 3 are obtained by fitting P to ȝ using ,…”

Simulations of an underground explosion in granite

“…Statically, the behavior of granite in triaxial compression was simulated at different levels of confining pressure. The numerical simulations closely resembled a series of experiments performed by Schock et al [4] to examine the yield, bulking and failure characteristics of Climax Stock granodiorite, the same rock formation where PILE DRIVER was detonated. These static simulations were used to determine the material parameters for the yield and bulking models.…”

Near Field Modeling of Spe1 Experiment and Prediction of the Second Source Physics Experiments (Spe2)

“…The model assumes the material is isotropic and applies the mathematical structure of plasticity theory to capture the basic features of the mechanical response of geological materials, including the effects of bulking, yielding, material damage, and porous compaction on the material response. This model has been shown to be in good agreement with the static data of Schock et al (1973), as well as explosion data in granite [Antoun et al (2001)]. One of the shortcomings of this model is that it does not account for directional effects associated with wave propagation.…”