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Cemented backfill is an important contribution to ground support, particularly in high stress conditions. The
rate at which strength, and more importantly stiffness, increases with time after placement of backfill is
crucial to the safe and reliable use of this technology, but is an area that is currently poorly understood. The
importance of the interaction between fill type, binder and water used during the hydration process and their
impact on the rate of gain of stiffness and strength is highlighted. The principle of effective stress is critical
to understanding how pore pressures generated during placement and consolidation of backfill affects the
loads on barricades used to retain the newly-placed fill. Based on laboratory and in-situ experimental work,
a constitutive model has recently been developed at the University of Western Australia that considers
strength and stiffness gain with hydration time, self-desiccation and the effect on pore pressures in the fill. A
comparison of pore pressures developed during the staged filling of a stope is used to illustrate the
versatility of the model when incorporated into a finite element package. The utilisation of this model
enables the choice of fill and binder combination to be optimised, and provides greater certainty in the use of
cemented backfill in high stress conditions.
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434 Deep Mining 07, Perth, Australia
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