Modelling of cut-and-fill mining systems – Näsliden revisited

Abstract

Over the period 1975-1980 an extensive rock mechanics research and development program was conducted at the Näsliden Mine, Sweden by a team of investigators from the Boliden Company, the University of Luleå and the Royal Institute of Technology (Stockholm). The overall purpose of the program was to evaluate the degree to which rock mechanics calculation methods, mainly finite-element models, could be used as planning instruments in mining operations. Specifically a series of models (finite element and others) were used to predict the response of the ore body, the hanging and foot walls, and the fill during cut-and-fill mining at the Näsliden mine. Predictions were compared to field measurements and modifications were made until a calibrated model which could be used for simulation of future mining at Näsliden emerged. The major results from this work which was performed under sponsorship of the Swedish Board for Technical Development (STU) and the Swedish Rock Mechanics Foundation, (BeFo) were reported at the International Symposium of the Application of Rock Mechanics to Cut-and-Fill Mining (Luleå, Sweden) in June of 1980. Although the values predicted by the final model were in general agreement with the measurements, some variation in both trend and amount of the fill pressures, wall convergence and pillar stresses were noted. One possible explanation was the difficulty of simulating the non-linear behavior of the fill using the finite element models selected. In this paper, the Näsliden data have been reevaluated using a technique that allows detailed modelling of the non-linear fill behavior and the stope pillars but greatly simplifies the reaction of the surrounding (wall) rocks. One-dimensional load-deformation curves for the fill determined using a split platen consolidometer have been incorporated into a filled slot analysis of the Näsliden cut-and-fill system. Actual and predicted fill pressures, wall convergence, and pillar stresses as a function of mining sequence are found to be in good agreement.