ABSTRACT
Room-and-pillar is one of the most well-known and widely used underground mining methods worldwide. Even though this method is traditionally linked with mining, its application serves as a cost-effective and versatile construction method for the development of large underground spaces for civil applications as well. The Tributary Area Theory (TAT) has been traditionally used for the estimation of the average pillar stress, the first step in the empirical methodology for the design process. Although TAT and the empirical pillar stress equations have been successfully employed, it is common knowledge that TAT tends to oversimplify and yet overestimate the stress imposed to the pillars.
The main aim of this paper is to analyze and evaluate the pillar stress conditions by directly comparing the TAT values and the pillar induced stresses through FEA. In this effort, a series of 3D and 2D numerical analyses were carried out under a series of various pillars’ configurations and initial virgin stress fields in order to properly decode the pillar loading regime and depict the deviation of stresses estimation. The authors suggest two (2) power equations for the direct estimation of the average major principal stresses developed upon the pillars’ crest, both for the case of rib & square pillars layout. The performance of the equations was found to provide results within high confidence levels in alignment with the results from 2D & 3D numerical analyses. In general, further room is left for improvement in terms of a more efficient and perhaps more aggressive pillar design maximizing the full potentials of the room-and-pillar method.
