Quasi-static and mechanical shock testing of reinforced shotcrete surface support

摘要

Mining ground control safety often depends on supporting, or at least containing, the ground between rockbolts. Different combinations of shotcrete and mesh are often used to provide surface support between bolts. Researchers with the National Institute for Occupational Safety and Health, Spokane Mining Research Division in Spokane, Washington, United States of America are measuring the mechanical performance of reinforced shotcrete used as ground support in deep underground mines where squeezing or rockbursting conditions pose significant ground control issues. Under these conditions, ground support must be able to absorb energy by yielding through large displacements while maintaining support capacity. Two test machines have been developed: (1) a high-energy high-deformation panel test for performing quasi-static tests on field-scale shotcrete panels restrained by grouted rockbolts, and (2) a fully-dynamic mechanical shock testing machine that has been retrofitted for testing 1 m square shotcrete panels. This paper describes these machines and results from commissioning tests. For the quasi-static machine, reinforcement of tested panels has included welded-wire mesh, chain-link fencing, synthetic fibres, spray-on polyurea liner, and combinations of these products. The dynamic machine is in an early stage of development, but results of several commissioning tests on chain-link, welded-wire, and fibre panels are discussed. Insights gained from laboratory testing may lead to ground support developments that improve safety in underground mines.