Benchmarking study by laboratory load transfer testing along full resin encapsulated rock bolts

The primary ground support used in Australian underground coal mines is a rebar rock bolt anchored to the rock mass using polyester resin capsules. The key objective of this research project was to benchmark different types of Australian rockbolt resin capsules, including relatively new formulations. Laboratory test methods were developed based on previous studies conducted in South Africa and subsequently at the University of Wollongong, which used 1.8 m JX bolts for installation in internally threaded steel pipes that simulated the borehole. The encapsulated bolts were cut into 80 mm long sections for push testing to obtain around 20 data points from each bolt. Different resin formulation variables were tested; these included three types of limestone fillers and two types of catalyst. The load transfer capacity ofdifferent resins were determined by evaluating the bond strength, peak strength and area under the push test curve. Significant variation in load transfer capacity was found along the length of all 1.8 m bolts tested. The load transfer capacity and its variations along the bolt length were evaluated to be a characteristic of the type of resin formulation tested. Some resin formulations produced upto 20% higher load transfer capacity with better consistency along the length of the bolt. Results from more than 300 push tests were used to assess and validate this study. The findings from this detailed research project can be used for a better understanding of the ground support performance of different Australian resin capsules.