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2013SprShotcreteEMag

Fig. 1: Plan and profile section of the shaft repair (Note: 1 in. = 25.4 mm; 1 ft = 0.328 m) that an upgraded structural steel support system placement areas. To pump the required distance, with a reinforced shotcrete shaft lining was the a high-slump, self-consolidating mixture was most time- and cost-effective option. designed with accelerator introduced at the One challenge to placing shotcrete on this nozzle. The product was to be pumped through project was that dust had to be minimized due a 2 in. (51 mm) line. A surface and procedure to the proximity of sensitive laboratory equip- test was conducted, including full-mixture ment. Conveyance of bulk prepackaged shot- testing and the production of test panels. Once crete material to the repair area was difficult the shotcrete mixture and placement techniques because of the available sizes of the shaft cages, were worked out, 2 in. (51 mm) slickline was and establishing an underground mixing plant installed in the shaft to the work area. at the available levels was impossible without After the shaft and steel support structure was extensive mining. Because of the physical con- temporarily stabilized, the final repair was straints underground, ECI selected to establish executed in stages from the upper limit of the on-site batching operations at the surface and damage to Level 27. The average stage length pump the shotcrete from the surface down the was 8 to 10 ft (2.4 to 3 m) and included removing shaft approximately 2300 ft (700 m) to the the steel sheeting between the support sets, Shotcrete • Spring 2013 19


2013SprShotcreteEMag
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