ABSTRACT
Existence of the density of coal joints and cleats are the most important factors complicating mechanical responses of a coal mass to stress loading. The joint and coal mass interaction and the mode of failure dominate the mechanical behaviour of jointed coal masses and the stability of coal excavations. The shear or mixed shear/tensile failure change to tensile failure by increasing the confining pressure, ligament length and ligament angle. This paper focuses on extending of a thermodynamic approach to constitutive modelling of the coal, with emphasis on developing local and non-local damage models based on the joint density and the joint dip angle. Effort is put on the construction of a consistent and rigorous statistically framework, which allows the incorporation of both local and non-local features into the constitutive modelling. This is an important feature in developing damage constitutive models based on trajectory of the failure surfaces in a coal mass. A particular attention is devoted to derive an equation to calculate the fracture energy which would be a function of the joint density either in a single or crossed conditions as well as the suggested damage constitute model.
