When you say overhead, people invariably think of fixed costs, salaries, and the general costs of running a business.
Freeport’s New Barmac Delivers High-Quality Shotcrete Sand
In November 1936, during a climbing expedition to the glacier-capped peaks of central New Guinea, Dutch Petroleum Geologist Jean Jaques Dozy discovered a massive copper mineralized outcrop
Shotcrete Spraying Machines for Immediate Support in Tunnels
Tunnels are important elements in modern industrial society.
Robotic Shotcrete Applications for Mining and Tunneling
If a robotic applicator is mentioned in connection with mining or tunneling and shotcrete, what is meant is an apparatus used to hold and control a spraying nozzle. Why should this be necessary when a man can do the same work? Tunneling and mining development are intrin-sically hazardous forms of construction. When shotcrete is used as initial temporary support after blasting, using a mechanical arm to extend into an unsupported area is a great enhancement to personnel safety.
Underground Shotcrete Quality Assessment
During the 1990s, the use of dry-mix shotcrete as a tool for ground support became much more prevalent in Canadian hardrock mines. With this increase in dry-mix shotcrete use came the need to develop a practical and accurate method for determining the quality of the in-place shotcrete. This report summarizes the results of a study undertaken to provide the basis of an under-ground shotcrete quality assessment program for hardrock mines.
Early-Age Test Methods for Fiber-Reinforced Shotcrete
Toughness is at least in part influenced by the compressive strength of the shotcrete matrix, so concrete strength is doubly important for ground control. In time-critical environments such as heading development in mines and most tunnels, the cost of excavation is often strongly influenced by the overall rate of progress; this, in turn, is influenced by the time to safe reentry. The minimum period of time that must elapse before it is safe to reenter under freshly shotcreted ground is directly related to the rate of strength gain in the shotcrete matrix.
Reentry into a Shotcreted, Underground Heading
Whether in a mine or a tunnel, the concept of keeping all people working under supported ground is an essentially sacred one. Even with the most stable ground, the risk of a ground fall causing injury to persons or possessions is greatly mitigated once proper support measures are installed. This becomes even more critical as the quality of the ground diminishes.
Quality Management of Shotcrete in North America
As for all construction materials, a proper program of quality management should be implemented in shotcrete construction to protect the owner™s investment. This article briefly examines typical shotcrete Quality Management (QM) practice in North America. QM can be considered to be comprised of Quality Assurance (QA) and Quality Control (QC) functions.
Shotcrete – The Repair Solution for the Memorial Tunnel
In 1953, the Memorial Tunnel in Standard, WV, was constructed as a two-lane, 2800 ft (853 m) tunnel with semi-transverse ventilation. The owner operated the tunnel until the mid-1980s when a four-lane bypass was constructed to upgrade the turnpike to current Interstate standards. The tunnel was abandoned until 1989 when the Federal Highway Administration (FHWA), in conjunction with the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), embarked on the Tunnel Fire Ventilation Test Program using funding from the Central Artery Project.
The test program consisted of performing controlled test ï¬res up to 100 megawatts. These intense ï¬res then provided valuable information for the design of ceiling wall partitions and the protection of facilities for power, ventilation, and lighting. In addition, it provided the opportunity to develop and evaluate methods of proper ventilation control of a tunnel under various ï¬re scenarios.
Parsons Brinckerhoff was retained to perform the test program. As part of that test program, an evaluation of the structural condition of the tunnel was performed and structural repairs were designed. A critical part of the design was to insulate structural portions of the tunnel for temperatures in excess of 2000 °F (1143 °C).
The rehabilitation program for the reuse of the tunnel required the sealing of all cracks in the tunnel liner because the bedrock around the tunnel contained low-flashpoint cannel coal. In addition to sealing the cracks, extensive structural rehabil-itation of the liner was performed to repair damage caused by the excavation for the bypass on the adjacent highway. Numerous products were evaluated to determine which would provide suitable fire protection for the structural elements of the ceiling and for mechanical equipment anchorages. The test program included the use of traditional venti-lation with a tunnel ceiling and tests with the ceiling removed for the use of jet fans. The construction contract for the rehabilitation of the tunnel and the removal of the ceiling had a projected cost of $10 million.
During the test program of 98 ï¬res, routine inspection of the tunnel was performed to evaluate the performance of the ï¬reprooï¬ng. Based on the performance of certain structural elements, changes were made in the use of structural ï¬re-prooï¬ng and code requirements for the protection of equipment. After the test program in 1991, the
The Use of Macro-Synthetic Fiber-Reinforced Shotcrete in Australia
Macro-synthetic ber-reinforced shotcrete (SnFRS) has rapidly gained popularity in Australia over the past 5 years. This can be attributed mainly to the huge improvement in post-crack performance that has been demonstrated over recent years and the almost universal adoption of this material for ground support by the underground mining industry.