What separates the support of mining openÂings from the support of similar civil engineering structures is the fact that mine openings have to survive large defonnations as a result of changing stress conditions induced by progressive mining. Steel fibers impart to concrete and shotcrete a high degree of ductility which not only allows the shotcrete and concrete linings to absorb important rock movements, but also to increase their bearing capacity by a redistribution of the loads.
The use of shotcrete for the support of underÂground excavations was pioneered by the civil engineering industry. In recent years, the mining industry ha,;; become a major user of shotcrete for underground support. The simultaneous working
Steel Fiber Reinforced Shotcrete, It is time to find out about it.
In an age when the building, tunneling, and in some areas, minÂing industry, is thriving in North America, we in the shotcrete industry should be looking for ways to increase productivity and save on ever-increasing labor costs. This type of thinking often requires the use of products that we either are not familiar with or have never used at all. Since we are in an industry where our chief concerns are keeping a safe workplace, while at the same time, trying to increase production or speeding up project compleÂtion time, we are often times unwilling to try new technology because we are afraid of the unknown. We fear a decrease in proÂduction, having to buy new equipment, and worst of all, lostÂtime accidents.For this reason-the unknown-many shotcrete contractors and mine managers have shied away from the use of steel fibers in their shotcrete. Their arguments against using steel fibers are often the same. “We use mesh or rebar for reinforcement because we know for sure that the reinforcement is in place before we apply shotcrete. That way, we don’t have to worry whether or not we have added the correct amount of steel fibers, or if the steel fibers are mixed uniformly, or if the fibers will do the job at all.” Or, we hear the all too familiar response, “If it is not broken, don’t fix it.”
In my opinion, this “if it is not broken, don’t fix it” attitude is keeping a lot of shotcrete contractors from increased production and greater financial successes. Sure, the economy in North America is strong now in the
Moab Khotsong Mine, A Mining Engineer’s Perspective on the Application of Steel Fiber Reinforced Wetcrete as a Support Medium in an Ultra Deep Level Mine, Part 1
A Mining Engineer’s perspective on the Application of Steel Fiber Reinforced Wetcrete as a Support Medium in an Ultra Deep Level Mine.
Steel Fiber Reinforced Shotcrete Replaces Cast Concrete Lining, World’s Longest Subsea Road Tunnel
The Northcape Tunnel in the Artic Circle in Norway was opened for traffic on June 15, 1999. The project is the longest subsea road tunneltunnel (6820 m or22,000 fl) in the world un1il 1999/ 2()0(). TheNorthcapc¢Tunnel is part of 1he FATIMAÂProject, (he road connection from the mainland of Norway 10 the island of Mager!lya and 1he Northcapc. During the tunneling¢period, many probÂ
Evolution of Fiber Reinforced Shotcrete
The concept of reinforcing shotcrete with discrete, disominous steel fibers was developed by the Battelle Research Corporation in the USA in the early 1970s.
Shotcrete Design and Construction for the Stave Falls Project Power Tunnels
BC Hydro has recently completed construction of a replacement power plant at Stave Falls, near Mission, British Columbia. Two new power tunnels were constn1cted to carry water from the intake to the new powerhouse. The crown, walls, and invert of the power tunnels were fully lined with steel fiber-reinforced shotcretc for the primary purÂpose of reducing the hydraulic roughness of the drill and blast tunnel surfaces. Shotcrete was also used for the geometric transition from the horseshoe-shaped, shotcrete-lined tunnel to the circular steel lining.
Shotcrete for Underground Support in Brazil
Shotcrete has been used in Brazil since the 1950s, mainly in minor works of slope stabilization and repairs in concrete structures. It was only in the 1960s that it started to be used in underground work. The Furnas Hydroelectric Project had some sections of its diversion tunnels, where the ground was a highly fractured and weathered quartzite, lined with steel bar reinforced shotcrete. The good perÂformance in Furnas led many other hydroelectric projects to adopt shotcrete lining in their tunnels, replacing previously specified cast concrete.
Shotcrete Applications at Northparkes E26 Mine
Shotcrete was used extensively during construction of Northparkes E26 Underground Mine, Australia’s first block cave mine. Applications for the shotcrete included ground support, ground control, construction, safety, protection of equipment and remedial repairs. This article details the various uses for the 16,700 m3 (22,000 yd3) of shotcrete applied at Northparkes, the experiences gained during conÂstruction, and discusses whether the design expectations have been achieved.
Estimating Volume of Shotcrete for Mining Applications
Traditionally, there has been a rather ad hoc attitude toÂwards technical supervision of mining engineering ground control programs, to the extent that the preparation and enforcement of specifications has not been a major issue. In certain locations, however, the dominant use of conÂtracting companies to provide mining-related services has meant that structured specifications are needed to ensure the high quality of the end-product. This is perhaps parÂticularly the case with shotcrete (1) now that more and more mines are using the process and product to enhance the ground control regime within the mine.
Shotcrete Reinforcement
Before the 1970s, shotcrete was reinforced either with conventional reinforcing steel welded wire mesh fabric, or in some inÂstances with chain-link mesh or even chicken mesh. In the early 1970s the con-Dr. D.R. (Rusty) cept of steel fiber reinforced shotcrete