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For the stability and deformation analysis of open-cut mines using numerical methods, one critical step is to identify and simulate the elastoplasticity of geomaterials comprising the open-cut batters. The Victorian Brown Coal (VBC) in Australia is a non-textbook geotechnical material with a hardening feature in compression leading to brittle failure while showing a sharp post-peak softening behaviour. In order to study different aspects of elastoplasticity including the hardening and post-peak softening behaviour of the VBC, a series of laboratory tests including one-dimensional oedometer and triaxial tests were carried out on undisturbed VBC specimens taken from 30 m to 50 m below the ground level in one of the largest VBC open-cut mines in Victoria. By post-processing of the triaxial and oedometer test results, a yielding phenomenon was identified at the boundary between the fully elastic and elastoplastic domains. The magnitude of the material stiffness in the elastic domain was found to be independent of the confining pressure in triaxial tests while governed by the chemical bonding of the coal particles. The post-yield behaviour, however, was a frictional hardening and ruled by the magnitude of the confining pressure leading to a failure envelope sensitive to the organic content of the material. In this paper, a unified failure envelope is defined for the VBC using the Hvorslev-type normalisation process. Furthermore, a nonlinear elastoplastic constitutive model was examined to describe the elastoplasticity of VBC in triaxial condition, which led to a good agreement between the experimental and numerical modelling results. • Different aspects of elastoplasticity of an Australian Soft Rock (VBC) were studied. • A series of laboratory tests, including oedometer and triaxial tests, were carried out. • The material stiffness in the elastic domain was found to be stress-independent. • The post-yield behaviour was found to be stress-dependant frictional hardening. • The failure envelope was found to be sensitive to the organic content of the material. [ABSTRACT FROM AUTHOR]

• The DDA simulates the mining-induced rock avalanche. • The failure process of the landslide was numerically identified. • The simulated failure process correlates well with the expert image and the local landform. This study numerically simulated the failure process of a mining-induced landslide at Nattai North, Australia. Results obtained using Discontinuous Deformation Analysis (DDA) matched the conceptual failure process suggested by local geologists and the observed maximum run-out distance. The maximum velocity of the sliding rocks exceeded 40 m/s. Computational results showed that the slope with inward sub-horizontal bedding planes and sub-vertical discontinuities remained stable if the mining-induced high principle stresses did not fracture the rocks near the slope toe. Failure of the rocks near the toe of the slope was a key causal factor in the subsequent landslide. This paper presents the first numerical simulation of the post-failure behavior of the mining-induced landslide at the Nattai North site. It also represents the first DDA simulation to clarify the chain reaction of a mining-induced landslide and demonstrate its applicability in such investigations. [ABSTRACT FROM AUTHOR]