COSFLOW is a coupled 3D mechanical deformation and duel porosity multiphase flow finite element code developed at CSIRO. A unique feature of COSFLOW is that in its description of load-deformation behaviour of layered rocks it incorporates the Cosserat theory, which is found to accurately and efficiently simulate mining induced stress and deformation in coal measure rocks. In the Cosserat model, inter-layer interfaces (joints, bedding planes) are considered to be smeared across the mass, i.e. the effects of interfaces are incorporated implicitly in the stress-strain model formulation. An important feature of this model is that it incorporates bending rigidity of individual layers in its formulation and this makes it different from other conventional implicit models yielding an accurate definition of load deformation behaviour.