Mechanical behavior of backfilled pillar under biaxial loading

Abstract

Backfilling the pillar to form a pillar-backfill collaborative bearing structure is the key to cut and fill method. The pillar-backfill bearing system is also an important support structure to maintain the stability of the underground stope. This paper analyzed the load-bearing capacities and failure modes of the backfilled pillars through biaxial compression tests, and the combined effects of lateral stress, fill ratio, and backfill mechanical properties were investigated. The results showed that the mobilized interface friction force between the pillar and backfill (fill ratio <100%) and effective backfill strength (fill ratio=100%) increased faster than pillar strength with lateral stress gain, which were the main reason for the increase in the load capacity of the backfilled pillar under biaxial loading. In addition, due to the significant stiffness difference between the pillar and backfill, the effective strength of the backfill in the biaxial loading test was lower than uniaxial compressive strength. The increase of lateral stress could not only improve the interface friction and the effective strength of backfill, but also affect the failure modes of the pillar and backfill. The experimental results will have reference value for studying the interaction of pillar-backfill structure.

Keywords

backfilled pillar / lateral stress / fill ratio / interaction mechanism / failure modes

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