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2014SprShotcreteEMag

Goin’ Underground Does Dry-Mix Shotcrete Have to be Dusty? By Joe Hutter Aso-obvious. Although the generation of dust can be controlled at the source so that less dusteffect on the generation of dust. This statementcan be attributed to the fact that dust generationn underground environment is often fraughtwith hazards—some obvious and some not- may not have obvious, immediate effects, it is needs to be removed from the atmosphere (Fig.1). recognized as a hazard that can have long-term health effects on the personnel who work in the Dry-Mix Shotcrete Materials mining and tunneling industry. It is important to address the causes of dust generation and to and Equipment recognize what we can do to minimize the effect When it comes to the production of airborne of this common hazard. dust, not all dry-mix shotcrete materials and During the development cycle, high amounts equipment are created equal. Doing your home- of dust can be generated through the processes of work by researching a materials and equipment extraction, drilling, blasting, crushing, conveying, supplier who has the benefit of experience and shotcreting. With the exception of the shotcrete working in an underground environment will process, dust generated by each of these processes contribute greatly to a clean, trouble-free under- must be controlled by ventilation, water sprays, ground shotcrete application. or dust collectors. While each of these methods Reducing dust at the source can be achieved of dust control can be effective, all require that by adhering to the following accepted practices: dust particles be removed from the atmosphere. • Bulk tote bags—When using prepackaged The problem lies in the fact that once the dust is materials, consider purchasing shotcrete airborne, it is always harder to control. materials in bulk tote bags, which generally From the perspective of a shotcrete operation, release materials into the machine hopper it is safe to say that when placed by an experienced, through a chute at the bottom of the bag. One properly trained crew using well-maintained of the greatest sources of airborne dust is equipment, dry-mix shotcrete can have minimal created when small 66 lb (30 kg) bags are broken into the hopper of a shotcrete machine. • Hopper hoods—When using bulk tote bags, a hopper hood, manufactured to fit the hopper of the shotcrete machine, will seal the hopper and prevent dust from being released (Fig. 2). Most shotcrete equipment suppliers will be able to supply a hopper hood with their shot- crete machine. Otherwise, many can custom- fabricate a hopper hood to fit any machine. • Equipment maintenance—Keep the shotcrete placement equipment well-maintained. Inspect wear pads and plates to ensure they are well- sealed to prevent dust from escaping the machine. Some shotcrete equipment manufac- turers will supply machines with lubricating capabilities to extend the life of wear pads and Fig. 1: When placed by an experienced, properly trained crew using wear plates and better seal the system. well-maintained equipment, dry-mix shotcrete can have minimal effect on • Exhaust port—Rotary-style dry-shotcrete the generation of dust machines are designed with an exhaust port 30 Shotcrete • Spring 2014


2014SprShotcreteEMag
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