Yielding pillar design in South African collieries
Date
1997
Authors
Oldroyd, Oldroyd
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Abstract
Three cases of pillar failure on Southern African Collieries have been studied to
analyse the behaviour of both the pillars and the overlying strata. Each of the cases
shows a different type ofpillar and strata behaviour during failure and thus provides
an opportunity for back analysis.
In the first case, pillars failed in a controlled fashion while the overlying strata behaved
in an elastic fashion. In the second pillars failed in a controlled fashion while the
surrounding strata behaved inelastically. In the third failure was initially controlled but
became uncontrolled.
Computer models have been run to determine the theoretical critical post peak pillar
slopes and the results of these models have been compared with the actual pillar
behaviour as derived from in-situ measurements during failure and that which might
be predicted from the theory of controlled and uncontrolled pillar failure.
Comparisons are also made with the expected behaviour implied from the results of
in-situ strength tests carried out on small coal pillars to ascertain their load
deformation characteristics. The results indicate that the behaviour of the pillars more
closely resemble that predicted from in-situ tests carried out by Van Heerden4• The
results also indicate inadequacies in using elastic methodologies to determine whether
pillar failure will be controlled or uncontrolled.
Description
A project report submitted to the Faculty of Engmeering, University of the
Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the
degree of Master of Science in Engineering.
Keywords
Coal mines and mining, Mining engineering, Barrier pillars, Rock mechanics, Coal mines and mining -- Safety measures, Coal mines and mining -- Data processing