  A mix-mode cohesive fracture model considering tension, compression and shear
material behaviour is presented, which has wide applications to geotechnical
problems. The model considers both elastic and inelastic displacements.
Inelastic displacement comprises fracture and plastic displacements. The norm
of inelastic displacement is used to control the fracture behaviour. Meantime,
a failure function describing the fracture strength is proposed. Using the
internal programming FISH, the cohesive fracture model is programmed into a
hybrid distinct element algorithm as encoded in Universal Distinct Element Code
(UDEC). The model is verified through uniaxial tension and direct shear tests.
The developed model is then applied to model the behaviour of a uniaxial
compression test on Gosford sandstone. The modelling results indicate that the
proposed cohesive fracture model is capable of simulating combined failure
behaviour applicable to rock.
