Laboratory simulation of the stresses within inclined stopes

Abstract

In the process of mining for earth resources, large underground voids called stopes are created that are later backfilled. For stability analysis of the backfilled stopes, it is necessary to understand the stress developments within the stope while the filling is in progress. Due to an arching effect, a substantial fraction of the fill weight is carried by the stope walls, depending on the physical characteristics of the walls. This paper describes the development of a laboratory model that simulates mine backfilling in an inclined stope and enables determination of the average vertical stress at any depth within the fill. The experimental results are validated against numerical models and stresses determined from an analytical expression. The effect of arching is the least when the stope is inclined at about 80 degrees to the horizontal, giving highest vertical stresses at any depth. This fact is not captured in both the mathematical and numerical models developed in the past and the ones discussed herein. The model tests show that the lateral earth pressure coefficient is closer to K-0 for vertical stopes and k(a) for inclined stopes. In the case of walls with dissimilar frictional characteristics, the analytical expression can still be used with an average value of the wall-fill friction angle.