Abstract:
This paper describes the evaluation of a limit equilibrium model to
simulate the behaviour of crush pillars in platinum mines. An
analytical model was derived to calculate the residual average pillar
stress (APS) values of the crush pillars. The values predicted by this
model were compared to the numerical values obtained from TEXAN
simulations. In general, the limit equilibrium model appears to be
very attractive for simulating pillar failure as the gradual crushing
of the outside of the pillar and the transfer of stress to the intact
core can be replicated. The value of the TEXAN crush pillar model
was further demonstrated by simulating an idealized layout with
crush pillars between two adjacent panels. The simulations
illustrated that oversized pillars will not crush close to the face and
this may lead to seismic failure in the back area. An important
finding of the study is that closure measurements may prove to be a
very valuable diagnostic measure in crush pillars layouts. Distinct
differences in magnitudes of closure were simulated for a scenario
where the pillars crush as expected, compared to the scenario where
an oversized pillar is left. Experimental closure data collected in a
crush pillar stope provided further evidence regarding the value of
closure measurements in these layouts.
