Modelling quasi-brittle fracturing of rock using hertzian stress distribution

This paper describes research conducted to investigate the fracturing process during indentation of rock using Hertzian stress distribution coupled with fracture mechanics principles. The rock to be indented was smeared with a uniform random distribution of micro-cracks (to represent pre-existing micro-cracks), with fractal dimension of 1.5. The micro-crack length (2c) ranged from 0.5 mm to

1.5 mm (order of the grain size) in random directions in the rock specimen. The 3D Hertzian stress field induced by the contact of a hemi-spherical indenter on flat semi-infinite rock surface was used. The indenter was assumed rigid. The crack propagation mechanism was modified to take into account the variation of stress over the crack length. The fracture simulation conformed more or less to the experimentally observed damage beneath the indenter.