by Alexeev, A. D.; Revva, V. N.; Bachurin, L. L.; Prokhorov, I. Y.

Experimental results on rock deformation and fracture under true triaxial compression have revealed a misfit between strain state and stress state, strain state varying from generalized compression to generalized shear at σ₃ ≠ 0. This misfit can lead to data misinterpretation during the stress field reconstruction after unloading. Fracture of rock specimens under true triaxial compression occurs by a combined longitudinal/transverse shear and produces the highest dilatancy. An increase in the hydrostatic pressure level diminishes limiting values of shear strains and suppresses the dilatancy effect. A maximum of dilatancy coincides with a maximum of fresh surface area formed during the fracture of the rock. The generalized cleavage of rocks becomes energetically disadvantageous in a true triaxial compressive stress field. Some sandstone becomes more brittle under true triaxial compression (σ₂ ≠ 0) at low values of the minimal stress component (σ₃) due to high initial porosity and dilatancy.

DOI: 10.1007/s10704-008-9214-6
Online Date: 6/27/2008
Print publication date: 1/1/2008
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