Characterisation of confinement effect on jointed rock pillars using a Synthetic Rock Mass approach

X. Zhao, Y. Zhang
International Journal for Numerical and Analytical Methods in Geomechanics
3D, confinement effect, Discrete Fracture Network, jointed rock pillar, Particle flow code, Synthetic rock mass

Confinement effect on jointed rock pillars is numerically characterised in this research using a Synthetic Rock Mass (SRM) approach. The SRM is an integrated model incorporating a discrete fracture network within a Particle Flow Code 3D particle assembly. In this paper, the confinement effect on a 3D jointed pillar SRM model is investigated in a series of simulations, including biaxial compression tests and true and conventional triaxial compression tests.

The numerical results suggest that the applied confining stresses generally result in higher pillar strengths and ductile post-peak responses. More brittle post-peak behaviour is simulated in the biaxial and true triaxial tests when the pillar is confined by a high stress in one lateral direction and by a zero/low stress in the other lateral direction. This phenomenon is attributed to significant lateral pillar dilation in the less confined direction. Detailed pillar failure modes are monitored in the uniaxial and triaxial tests. Axial splitting fractures and long shear zones cutting through the pillar are simulated when the pillar is able to dilate in the direction of least confinement. Localised shearing along joints and failed rock blocks is the dominant failure mode when the pillar dilation is resisted by the applied confining stresses. The pillar remains relatively intact with limited cracking in the pillar core in the highly confined triaxial tests.

Keywords: jointed rock pillar, confinement effect, Synthetic Rock Mass, discrete fracture network, Particle Flow Code, 3D.

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