Non-destructive testing of deep mine anchorages

Anchorages are used throughout the coal industry for supporting tunnels leading to and from the active coal face. A large scale non-destructive testing programme using technology developed at the University of Aberdeen was undertaken at an underground coal mine on 264 anchorages in total. The paper discusses the effective free length results and the subsequent detailed statistical analysis of the diagnosis. A number of different scenarios for the anchorages were developed based on their specific attributes, with each scenario comprising a newly developed mathematical model of the anchorage system. This analysis indicated that a number of anchorages had failed. Subsequent exhumation of the anchorages identified by this process by the mine operator confirmed this conclusion. In addition, analysis of the effective free length diagnosis shows that at the time of testing some of the anchorages did not fit the design specification at installation. This has important implications for similar anchorage installation in other environments and a number of explanations for this difference are given.