Compactive Cataclastic Flow in Tuffeau de Maastricht Calcarenite: Mechanical Deformation & Permeability Reduction

Abstract

The mechanical behavior and permeability of the Tuffeau de Maastricht calcarenite under compactive cataclastic flow have been studied. The model used to back-test analyze the experimental results was the one developed by Lade and Kim, which employs all three invariants. The model parameters were calibrated based on conventional triaxial and hydrostatic experiments. In order to predict the formation of localization zones, bifurcation analysis was applied. The localization point was identified to be the onset of shear-enhanced compaction (a threshold in differential stress after which significant reduction of porosity is induced). The numerical results proved to be in good agreement with the experimental ones. As for the permeability measurements, K-constant as well as conventional triaxial experiments were conducted. The effective mean stresses were in the “transitional” regime between brittle faulting and cataclastic flow. Before the onset of shear-enhanced compaction, permeability was primarily controlled by the effective mean stress, independent of the deviatoric stresses. With the onset of shear-enhanced compaction, however, coupling of the deviatoric and hydrostatic stresses induced considerable permeability and porosity reduction.