This paper describes the application of a three-dimensional finite element
modelling tool to help assess the stability of a highwall at a Central
Queensland mine following the weakening of its base due to highwall
mining. With traditional stability assessment techniques, likely failure
modes are identified on the basis of previous experience and structural,
sedimentological and geomechanical data and a mechanistic analysis of
these individual modes is performed. The value of the full
three-dimensional model over these traditional techniques is that it
provides a coherent approach to assessing highwall stability without the
necessity of initially deciding upon the dominant failure mechanism and
gives a useful adjunct to the traditional tools. The three-dimensional model assumes the rock mass is made of
elasto-plastic blocks, incorporating possible planes of weakness,
separated by near horizontal joints. The model includes the relaxation of
stresses due to the excavation of the highwall and incorporates estimates
of blast damage near the highwall surface