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2015FallShotcreteEMag

Materials Handling Underground By Craig McDonald and Julian Peña Cruz Mof materials and equipment in an under- shotcrete or concrete can carry between 4 and 9 yd3) of material per load. The drum or3Most bulk haulage equipment designed for(3 and 7 materials and equipment handling can bechallenging in any industry. Movement ground environment, however, has its own unique bins are charged on the surface and driven under- challenges. Once supplies arrive at the surface of ground via the ramp, where they are discharged the jobsite, they must be sent underground through and then returned to surface so the process can be a network of tunnels to the work site where the repeated. This type of delivery method is reliable supplies are required. For some mines and tunnel and efficient. However, many mines and tunnel projects, access underground is available by a projects do not have the luxury of being able to ramp from the surface. For others, access to an use it due to lack of ramp access. underground worksite may only be available Mines and tunneling projects serviced only by through a vertical shaft with an elevator or cage a shaft often use bulk bags or super sacks of that travels from the surface to the various levels. preblended material to overcome shotcrete supply In either case, the shaft or ramp usually becomes challenges. Bags containing 2200 to 3300 lb a literal bottleneck in the process of getting materials (1000 to 1500 kg) of material are shipped to the to the worksite. site on pallets, where they are stored until used. Like all jobsites, each mine or tunnel project In most cases, the site is accessible by road and has its own unique challenges. Shallow mines shotcrete materials can be delivered directly on with ramps from the surface have the ability to flatbed trucks. In certain cases, however, use bulk haulage equipment to transport shotcrete extremely remote sites require a more challenging materials and equipment to the heading. In the strategy. Some remote northern mines, for case of wet-mix shotcrete supply, material is example, can only be accessed by “ice roads” delivered in trans-mixers, which travel via the made popular through the television show Ice ramp to the worksite or heading. For dry-mix Road Truckers. For other remote locations, the supply, bulk bins mounted on underground only economically viable solution is to transport haulage vehicles can be used to transport bulk the material by boat. In both of these cases, the dry-mix shotcrete to the worksite (refer to Fig. 1). dry-mix material should be packaged in heavy- duty bulk bags with the additional protection of an inner polyethylene barrier. This added protection will reduce the possibility of moisture (in the form of water or snow) from coming in contact with the dry shotcrete material and causing the mixture to hydrate prematurely. When transporting shotcrete by boat, smaller volumes are best shipped in 20 ft (6 m) shipping containers, which generally hold a maximum of 53,000 lb (24,000 kg). For larger volumes, bulk bags can be directly loaded into the hull of a vessel dedicated specifically for shotcrete material transport (refer to Fig. 2). Whether a remote mine site in the far north or a local tunneling project located a few miles (few km) from the production plant, preblended, ready-to-use bags of shotcrete must be stored on-site until the surface crews are required to transport the material underground to the shotcrete crew. Once the material is delivered to the worksite, the Fig. 1: Bulk dry shotcrete hauler/sprayer shotcrete crew will be able to begin the shotcrete 22 Shotcrete • Fall 2015


2015FallShotcreteEMag
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