Mecânica das rochas

Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. Vol. 31, No. 6, pp. 687-698, 1994

Pergamon

0148-9062(94)E0002-J

Copyright ,ffS~1994 ElsevierScienceLtd Printed in Great Britain. All rights reserved 0148-9062/94 $7.00 + 0.00

Designing Mine Pillars with the Convergence-Confinement Method
D. E. GILLt M. H. LEITEt D. LABRIE~

This paper shows how the convergence-confinement method can be extended to predict the axial stresses in pillars in uniform and non-uniform multiple pillar arrays. The conventional graphical method, which allows the dimensions of single pillar and uniform two-pillar arrays, is first extended to uniform arrays consisting of three and four pillars and then to non-uniform arrays consisting of two pillars. As graphical solutions are not feasible when the number of pillars in uniform arrays is greater than four or when the number of pillars in non-uniform arrays is greater than two, an algorithm which makes use of the pillar reaction curves is proposedfor predicting the axial stress acting on each pillar of the array. Some of the axial pillar stresses predicted with the proposed extensions of the convergence-confinement method are compared to those obtained with other prediction methods. Features of the proposed algorithm are briefly discussed.

INTRODUCTION Mine pillars are blocks of ore left between productive excavations. Their function is to control rock mass displacements throughout the zone of influence while mining proceeds. Such a support system is often called "natural support" [1]. Although differences exist between the way in which mine natural support systems are generated, an economic design of pillars must always satisfy two conditions: the amount of ore left in place must be kept to a minimum and it must fulfil the requirement of assuming the global stability of the mine structure. There are two fundamental approaches to the design of mine pillars. With the first one, a detailed determination of the state of stress