Structural uses and placement techniques for lightweight concrete in underground mining

"The U.S. Bureau of Mines conducted experiments on the use of lightweight concrete in the density range of 100 lb/ft3 for liners in underground mines. Three test sections were completed: a monolithic, portal-type structure with integral walls and arch constructed aboveground; an underground test section constructed in a mine drift using plywood forms; and a second section constructed in a drift using an air-supported formwork. The lightweight concrete in the two underground test sections was placed using piston pumps and a slickline. Fiber reinforcement was added to the concrete in the mine sections without any apparent problems with either pumping or placement of the concrete. In another experiment, the Bureau and Hecla Mining Company, Mullan, Idaho, used lightweight concrete in the density range of 25 lb/ft3 to replace timber blocking in a raise preparation structure. Other experiments are described in which low-density, lightweight concrete blocks were produced for mine ventilation doors, stoppings, and barricades. Other mine uses reviewed include pillars and collapsing beams. An advantage of low-density concrete is that it will display up to 50 pct deformation at a constant yield stress. These innovative concepts in deformable concrete lining systems will aid mine operators by decreasing capital and maintenance costs, increasing the available space in underground haulageways, and providing productivity gains and improved resource recovery in the soft, caving, squeezing, or bursting ground conditions often found in deep mines." - NIOSHTIC-2NIOSHTIC no. 10007308198

Assessment and optimisation of winze blasting designs for underground sublevel stoping

Winze blasting is the first and most critical step in the production cycle of underground sublevel stoping. Blasting design heavily relies on personal experience due to the lack of design guidelines and because very limited research has been conducted in the past. This research uses an empirical method to develop a design guideline and optimisation system for winze blasting. A winze blasting database was developed to collect data from three Australian sublevel stoping mines, and 68 cases using nine winze blasting patterns were recorded in a period of two years. An optimisation system or winze blasting calculator was introduced based on the database. The optimisation system analyses key parameters of the blasting data recorded in the winze blasting database, such as advanced height, void ratio, ground condition and cost. Then the system provides suggested firing height for winze blasting patterns investigated in this thesis. Besides, the system also provides guideline information about alternative winze blasting patterns, related firing height and cost for those patterns according to various ground condition. Analysis of the database found that the average firing height for winze blasting is 8.5 metres and most firings do not reach the optimal height. A new term void ratio efficiency factor was introduced to measure the maximum and optimal firing heights that can be determined by each percent of void ratio. Results show that the maximum void ratio efficiency is 3.34 m/% and the optimal level is from 0.71 m/% to 1.36 m/%. The average cost for developing a metre of winze is A$2,505 and average developing speed is 0.49 shift (12 hours shift) per percent of void ratio. The research also shows that one large reamer with fewer blast holes is better than a number of small reamers with more blast holes. The database can be used and shared across different sites to provide essential guidance for winze blasting design optimisation. The more data collected in the database, the more accurate the optimisation results can be

Proceedings : mechanics and mitigation of violent failure in coal and hard-rock mines

Papers presented at a U.S. Bureau of Mines (USBM) technology transfer seminar describe the causes of violent material failure in U.S. mines, measurement techniques for monitoring events that result in violent failure, and mitigation techniques for controlling failure. Specific factors contributing to violent failure are identified on the basis of geotechnical monitoring in 16 U.S. hard-rock and coal mines and on statistical analyses of 172 coal bump events. New monitoring and analysis techniques developed as tools for assessing violent failure; geotomographic methods that provide new capabilities for the study of material failure and stress changes over large areas; and seismic methods for determining source locations, calculating energy release, and determining source mechanisms are described. Fair correlations have been established among seismic parameters, elastic stresses, face support load, and violent events. USBM studies have identified the advantages using both yielding and stable pillars for coal bump control. A computer program has been developed as an aid for selecting room-and-pillar layouts. The practical aspects of implementing a destressing program is outlined for coal mines, while the importance of mine orientation and timely support installation in controlling buckling-type failure is identified for hard-rock mines.Papers presented at technology transfer seminars held May 1995 in Coeur d'Alene, ID, Price, UT, and Norton, VA.NIOSHTIC no. 2002460

Bleederless ventilation systems as a spontaneous combustion control measure in U.S. coal mines

"The U.S. Bureau of Mines conducted a worldwide literature review of bleederless ventilation practices to evaluate their use as a spontaneous combustion control measure in U.S. coal mines. Factors that must be taken into account in the design and use of these systems include seal construction, the use of ventilation control devices, the use of methane-drainage systems in gassy mines, and the ground control plan. Monitoring for the detection of spontaneous combustion and the control of methane when methane-drainage techniques are employed is critical to the successful use of a bleederless ventilation system. This report describes the types of ventilation systems used throughout the world and the spontaneous combustion risks associated with these systems. Methane-drainage systems used in conjunction with bleederless ventilation systems are discussed. Ground control considerations such as pillar design, entry stability, and seal usage are reviewed. Monitoring systems for spontaneous combustion detection, methane-drainage control, and behind seals are examined. Finally, methods for evaluating the spontaneous combustion hazard of a mining operation to determine when the use of a bleederless ventilation system is warranted are reviewed." - NIOSHTIC-2NIOSHTIC no. 10004943199

Barrett v. Hecla Min. Co. Clerk\u27s Record v. 3 Dckt. 43639

https://digitalcommons.law.uidaho.edu/idaho_supreme_court_record_briefs/7116/thumbnail.jp

Barrett v. Hecla Min. Co. Clerk\u27s Record v. 2 Dckt. 43639

https://digitalcommons.law.uidaho.edu/idaho_supreme_court_record_briefs/7115/thumbnail.jp

Proceedings Of The International Workshop On Numerical Modeling For Underground Mine Excavation Design

Numerical models play a significant role in the design of safe underground mining excavations and support systems. Advances in the capabilities of numerical modeling software, together with ever increasing computational speeds, have made it possible to investigate the very nature of the large-scale rock mass and its response to mining excavations. The improved understanding of the rock response obtained from modeling enhances our designs, resulting in greater stability and safety of the mining excavations. To help advance the state of the art in this field, the National Institute for Occupational Safety and Health organized the International Workshop on Numerical Modeling for Underground Mine Excavation Design. The workshop was held in Asheville, NC, on June 28, 2009, in association with the 43rd U.S. Rock Mechanics Symposium. The proceedings include 10 papers from leading rock mechanics and numerical modeling experts in the United States, Canada, Australia, and Germany. The papers address a wide range of issues, including various numerical modeling approaches, rock mass modeling, and applications in coal and metal mines

Metal- and Nonmetallic-Mine Accident-Prevention Course--Section 4

Circular produced by the U.S. Bureau of Mines to promote safety through a series of reports on accident prevention in mines. According the the scope statement, "This is the fourth section of the revised series of circulars that cover various phases of accident prevention in metal and nonmetallic mines; it give information on accidents and injuries from storing, handling, and using explosive in metal and nonmetallic mines and discusses the precautions by which they can be prevented" (p. 2)

Proceedings of the International Workshop on Numerical Modeling for Underground Mine Excavation Design

"Numerical models play a significant role in the design of safe underground mining excavations and support systems. Advances in the capabilities of numerical modeling software, together with ever increasing computational speeds, have made it possible to investigate the very nature of the large-scale rock mass and its response to mining excavations. The improved understanding of the rock response obtained from modeling enhances our designs, resulting in greater stability and safety of the mining excavations. To help advance the state of the art in this field, the National Institute for Occupational Safety and Health organized the International Workshop on Numerical Modeling for Underground Mine Excavation Design. The workshop was held in Asheville, NC, on June 28, 2009, in association with the 43rd U.S. Rock Mechanics Symposium. The proceedings include 10 papers from leading rock mechanics and numerical modeling experts in the United States, Canada, Australia, and Germany. The papers address a wide range of issues, including various numerical modeling approaches, rock mass modeling, and applications in coal and metal mines." - NIOSHTIC-2An efficient approach to numerical simulation of coal mine-related -- geotechnical issues / D. P. Adhikary and H. Guo -- A review of recent experience in modeling of caving / M. Board and M. E. Pierce -- Characterization of natural fragmentation using a discrete fracture network approach and implications for current rock mass classification systems / D. Elmo, S. Rogers, and D. Kennard -- Three-dimensional modeling of large arrays of pillars for coal mine design / G.S. Esterhuizen, and C. Mark -- Numerical model evaluation of floor-bearing capacity in coal mines / M. M. Gadde -- It is better to be approximately right than precisely wrong: why simple models work in mining geomechanics / R. E. Hammah and J. H. Curran -- An overview of calibrating and using the LaModel program for coal mine design / K. A. Heasley -- Deep coal longwall panel design for strong strata: the influence of software choice on results / M. K. Larson and J. K. Whyatt -- Practical application of numerical modeling for the study of sudden floor heave failure mechanisms / H. Maleki, C. Stewart, R. Stone, and J. Abshire -- Advanced numerical solutions for strata control in mining / A. Studeny and C. Scioredited by Gabriel S. Esterhuizen, Christopher Mark, Ted M. Klemetti, and Robert J. Tuchman."June 2009."Includes bibliographical references