The significance of mobile machine damage on the effectiveness of full-column resin grouted bolts

Abstract

This research study was undertaken to gain an understanding of the extent of the damage caused to full-column grouted resin bolts by collisions with Self-Propelled Mobile Machines (SPMMs). The primary purpose of the study was to determine whether damaged bolts must be replaced. The research consisted of push tests conducted on damaged bolts. To accurately reconstruct the extent of the damage caused by SPMM collisions, pipes were installed into the rock. Full-column grouted resin bolts were then installed into the pipes. After the resin was cured, the bolts were damaged using load-haul dump trucks. The pipes were then recovered and cut into 100 mm segments. Each segment was visually inspected to assess the extent of the damage to the resin column. Thereafter, the resin bond strength of each segment was assessed through push tests. The test results from each batch of tests were compared to a similar, undamaged control sample. The results show that, if the annulus between the bolt and the side of the hole was 4.5 mm or less, the resin damage did not extend beyond 100 mm, or roughly four times the diameter of the bolt, from the point of damage. For samples with an annulus of more than 4.5 mm, the quality of the resin column was compromised up to a depth of 400 mm, or approximately 20 times the bolt diameter. In the undamaged large annulus control samples, it was found that the lower 400 mm (from the hole collar) were poorly mixed. These samples achieved low push-out strengths as compared to the middle sections of the holes. The resin in the middle and upper portions of the holes also showed no detectable SPMM damage. The research concluded that the replacement of damaged full-column grouted resin bolts is only necessary if the annulus between the bolt and the hole is greater than 4.5 mm.