Evaluating methods of underground short encapsulation pull testing in Australian coal mines

In May 2012, an Australian Coal Association Research Program (ACARP) funded project C21011 commenced to develop coal industry standard test methods for assessing resin chemical anchors. The project was run by the University of Wollongong with assistance from Australia’s two resin anchor manufacturers, J-Lok and Orica. A program of field and laboratory studies was undertaken to examine various factors influencing effective the load transfer mechanism between the bolt/resin and rock to ensure test methods represented field performance. This paper discusses the field component of the research project. A series of Short Encapsulation Pull Tests (SEPT) were carried out in three mines with different geological conditions to determine the most representative and practical method of SEPT. Additional field work included installation of bolts into threaded steel tubes for subsequent laboratory evaluation. Factors of importance considered to affect bolt installation and the subsequent SEPT representing the fully encapsulated bolt performance included; borehole diameter, resin annulus thickness, installation time (including bolt spin to the back and “spin at back”), the effect of gloving and its impact on installation quality of the bolt and load transfer variation along the length of the installed bolt.