Experimental Study on Instability and Load Transfer Mechanism within Multi-Pillar System

Abstract

In order to study the instability and load transfer mechanism among multiple parallel pillars during underground mining, compressive tests on single- and treble-pillar specimens were conducted under soft loading condition with adjustable stiffness. Disc spring group was used to realize the adjustable stiffness of the test machine. Experimental results showed that the instability of rock specimen was determined by the stiffness of test machine, where the sudden jump displacement Δd exponentially decreases with the increase of loading stiffness. The load transfer behavior of treble-pillar specimen could only be reproduced under this soft loading condition. Under the soft loading condition, the failure of single pillar in multi-pillar system induces the sudden increase of cumulative AE counts not only in itself, but also in adjacent pillars, which indicates the accelerated damage in adjacent pillars accelerated by load transfer effect. Finally, it was concluded that the soft loading condition was the necessary condition for the load transfer of multi-pillar system. Results of this study may contribute to the better understanding of load transfer mechanism and to optimizing the design of room-and-pillar stopes during underground mining.