SHOTCRETE SAFETY AND ENVIRONMENTAL CONTROL

The paper which reviews health and safety considerations in the use of shotcrete, discusses the dust conditions, rebound problems and causticity problems, and suggests means of overcoming them. The problems which develop after the shotcrete has been in place (which include lack of strength, residual causticity and improper placement) are considered as well as the disposal of rebound and mine effluent to minimize the environmental contamination. The operator is subjected to high concentrations of dust, rebound, poor visibility and poor footing and his physical protection is important. Respiratory protection in the form of well-fitted respirators is mandatory for the gunning crew. Consideration, however, should also be given to others in the vicinity. Goggles or face shields provide protection from rebound but these could become covered from rebound. Means of overcoming this are described. Use of a boom to apply shotcrete eliminates the hazards to the nozzleman. Inadequate protection often leads to serious caustic burns for the people engaged in shotcreting. Good education, proper respirators and protective creams provide the best protection. Some dry-motar gunners have experienced a buildup of static charge on the hose and nozzle. Besides discomfort, the electrical discharge may ignite an explosive atmosphere if one were unknowingly present. A discussion of postshooting problems covers such aspects as the rate of strength increase, failure due to poor bond between shotcrete and rock or the lack of formation of a complete structure, fast-set-agents, the flow of water through the shotcrete area and out of the mine or tunnel, the disposal of rebound, and the problem of rebounding wire in the shooting of wire-filled shotcrete.