Serial decoupling of bolts in coal mine roadway supports

Abstract

Bolt supports within stratified strata in coal mines contribute to the unique characteristics of low-buried engineering structures such as tunnels or subways. Failure at the bolt interface is the main trigger of support failure in such settings. This paper comprehensively investigates the serial decoupling mechanism at a resin–rock interface, which is a process that occurs frequently in stratified strata. There are, however, different evolutionary processes that exist at the interface, from a total bonding stage to a plastic bonding stage, a slippage plastic bonding stage, a slippage plastic stage and a total slippage stage, sequentially. These processes accelerate the shortening speed of anchor life, whereupon axial force will fluctuate at each stage and corresponding equations can be derived successfully. Finally, a long-term field monitoring test which verifies the theoretical results and effective measures, such as pregrouting, can be used to prevent serial decoupling. The service life of the bolt system also can be prolonged.