Uniform Four-Foot Length Split Set Roofbolts vs. Uniform Four-Foot Length Fully Grouted Resin Roofbolts: Fid-Bau Portal

Uniform Four-Foot Length Split Set Roofbolts vs. Uniform Four-Foot Length Fully Grouted Resin Roofbolts

J. Maher

A study of roof behavior in an area bolted with fully grouted resin bolts and split set roofbolts was conducted in two concurrent phases of field testing. A study of the mechanics of fully grouted resin bolts and split set roofbolts was conducted in phase 1 testing. Both bolting systems were found to incorporate friction as the primary means of anchorage. The fully grouted resin bolt was found to be capable of about 2,000 pounds of anchorage per inch of grouted rebar and the split set roofbolt was found to have anchorage capacities in the range of 125 to 300 pounds per inch of bolt in contact with the roofbolt hole. Thus the fully grouted resin bolt can be classified as rigid or nonyielding compared with the split set bolt as yielding. A study of the behavior in an area bolted with split set roofbolts was compared with that in a similar area bolted with fully grouted resin bolts in phase 2 testing. In both areas, nominal mine design parameters were the same with bolts being 4 feet long and nominally spaced 4 feet center to center. It was found that both systems functioned adequately to support blast damaged or otherwise fractured roof rock. Roof movement was found to be less in the area bolted with the more yielding split set roofbolts. Test data and observations, however, indicate this finding to be attributable to more competent roof strata resulting from proper and controlled blasting techniques.