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By Xiaochun Xiao, Xin Ding, Yishan Pan, DI WU, Xiangfeng Lv

Rockburst is a sudden disastrous instability of coal mass that poses a serious threat to underground exploitation of coal resources; therefore, approaches of prediction and control methods are valuable for improving mining environments. The mechanical properties and bursting liability of coal with drying, under-saturated, and saturated moisture content under uniaxial compression are investigated, and the charge induction signal during coal deformation both in the laboratory and on-site is recorded in this study. The presence of water reduces the cohesion and increases the internal stress caused by non-uniform deformation of minerals, resulting in the strength, elastic modulus, and bursting liability being weakened. The charge induction precursor main frequency band is 1–100 Hz and belongs to the very-low-frequency signal regime, and it indeed varies with the loading stage, leading to specimen failure owing to changes in amplitude and continuity of the charge pulse in both the time and frequency domains. Water inhibits the richness of charge induction and reduces the bursting liability, and the earlier the precursor appears, the more total charge emerges. Moreover, measurement results indicate that the amplitude and continuity of the charge pulse decrease over a longer time, as recorded in a coal seam with water injection, further verifying the weakening of the coal dynamic characteristics. Charge induction can be a valuable tool with which to obtain the precursors for rockburst and to aid the evaluation of water injection.

Dec 26, 2022

By Robert E. Thurmond

With modern exploration techniques, it seems likely that an increasing number of the orebodies to be found in the future will be under alluvial fans or valley fill. As a result, a larger proportion of open pit mines will be confronted with the necessity for removal of substantial quantities of alluvial overburden; whereas in the past, for the most part, the open pit mine operator has dealt mainly with hard rock. If this proves to be the case, methods, equipment, and costs for alluvium stripping will become an increasingly important factor in open pit mine planning. Several operations are now faced with this situation, and various methods and equipment are used. At Pima Mining Company's operation the stripping ratio is in the range of 6/1 Well over half of the stripping volume is alluvium. The alluvium is removed almost entirely by carryalls hauling direct to a waste dump. Some removal has been accomplished by shovel and truck operation; more will be done by this means in the future. At American Smelting and Refining Company's neighboring .Mission Mine, nearly all alluvium removal is by large shovels and, trucks. U. S. Borax's Boron operation is accomplishing alluvium removal with carryalls but has been investigating other methods and equipment. The various operations in the Gas Hills Uranium District in Wyoming are stripping mainly with carryalls, although some small draglines are employed. The M. A. Hanna Company in the Mesabi Range employs large draglines and conveyor systems for removal of glacial fill. Nchanga Consolidated Copper Mines in Northern Rhodesia strips overburden with a large excavating wheel and conveyor system. There are no doubt other open pit operations with which the writer is not familiar, that are handling large quantities of alluvial overburden.

Jan 1, 1963

By Raja V. Ramani

Worldwide, promulgation and enforcement of health and safety laws and regulations have been the primary means of ensuring minimum and uniform standards of health and safety in the mining industry. In U.S. coal mines, a new era was ushered-in in 1969 for the control of health hazards from respirable coal mine dust. Since then significant progress has been made on all aspects of the respirable dust problem-its definition, monitoring, reduction, and control. In the intervening years, our ability to monitor, analyze, and characterize the mine atmospheric environment and the health of miners has increased many fold. Also, advancements in production technology have far outdistanced enhancements in environmental control technology. Therefore, questions are continuing to be raised on the adequacy of the characterization and control measures with regard to both the airborne respirable dust in mines and the health effects of respirable dust. Late in 1995, the Secretary of Labor appointed an Advisory Committee on the Elimination of Pneumoconiosis Amona Coal " Mine Workers (Dust Advisory Committee) to review the progress towards elimination of coal worker's pneumoconiosis (CWP) and silicosis, and in the program to control respirable coal mine dust in underground and surface mines, and make recommendations including improved standards and other appropriate measures for the control of exposure to airborne coal mine dust. The Committee's report was released in October, 1996. In this paper, a summary of the recommendations of the Committee is presented. A brief discussion of the background, and the issues and findings leading to the recommendations is also presented. The Committee concluded that the progress made towards making mines safer from the health hazards of respirable coal mine dust is substantial but that it is not sufficient to achieve the intent of the 1969 Coal Act. The Committee's recommendations encompass a wide range of issues addressing permissible exposure limits (PELS), sampling, dust control plans, hazard and medical surveillances, role of miners, training, and research and development.

Jan 1, 1997

By Vern Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western porphyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized -1+1/2-inch (-2.5+1.3-cm) ores from the Kingston (0.9 pct CU) and Centennial (1.6 pct Cu) mines of Upper Michigan. Concentrates of 4.0 pct and 7.5 pct Cu, respectively, were obtained at recoveries of 85 and 80 pct of the copper in the feed. Eighty percent of the sorted ore was rejected as tailing. Sorting larger fragments improved the separation efficiency. Tests on -4+2-inch (-10+5-cm) sized Kingston (1.6 pct Cu) and Centennial (2.1 pct Cu) ore samples yielded concentrates of 4.3 and 4.5 pct Cu, respectively, with corresponding recoveries of 92 and 91 pct. About 60 pct of the sorted ore was discarded as tailing. Porphyry copper sulfide ores also responded to electronic sorting but at a lower separation efficiency. Sorting response was affected by the degree of segregation.

Jan 1, 1976

By C. D. Iles

The philosophy used in designing and writing Duval's Sierrita mine design programs is discussed. The Sierrita Incremental Design system (SID) is reviewed with emphasis on Pushback Extraction Design (PED). FED is a method by which predesigned pushbacks are sequenced into an optimized period-by-period design that can be directly utilized in daily operations as well as intermediate and long range planning. The advantage of SID is that it provides a practical, mineable open pit design. PED is not a theoretical design system; it is in operational use.

Jan 1, 1981

By Morgan M. Sears, Gamal Rashed, Michael M. Murphy, Brent Slaker

In this study, a parametric study was conducted using FLAC3D numerical models to examine the impact of oblique loading, generated from seam dip, on the strength and the failure propagation pattern of a stone pillar using two simplified geometry types. In type 1, the sidewalls of the pillars were assumed to be perpendicular to the roof and the floor, while in type 2, the sidewalls of pillars were assumed to be vertical. The complex pillar geometry in dipping mines was frequently modeled using these two geometries. To capture a complete picture of the effect of seam dip on pillar stability, the modeled width-to-height (W/H) ratio of the pillars, in situ stress field, and pillars roof/floor interfaces were systematically varied to account for the potential distribution of values for these parameters across the underground stone mines in USA. Results from the numerical modeling indicate that dipping pillars have reduced strength compared with horizontal pillars. Also, an asymmetric failure propagation pattern could be obtained depending on an interaction between the W/H ratio, seam dip, in situ stresses, and pillar geometry.

Feb 5, 2021

By VIVEK KUMAR HIMANSHU, Murari Prasad Roy, Kaushik Dey, Rakesh Kumar Singh, Ashish Kumar Vishwakarma

Sublevel stoping is the most popular and practiced mining method in underground hard rock mines. Proper planning and its execution is the key requirement for stope extraction using this method. The stope extraction has been a challenging task since decades. The major reason is the unavailability of free faces as compared to opencast bench blasting. The geological and geotechnical parameters change gradually even within the stope itself. So, the blast design parameters should be planned according to the scenario of the upcoming ring. The blast design parameters like burden, toe spacing, inclination of blastholes, diameter of blastholes, charge density of explosive, etc., play an immense role in the rock damage. For the proper breakage of rock, the movement of burden is the prime objective. To study this, an explicit dynamic based modeler of M/s Ansys was used. The burden values were varied from 20 to 65 times of blasthole diameter to assess the optimum burden value during the study. The models were simulated for the rock having uniaxial compressive strength as 35 MPa and 102 mm blasthole diameter. Three holes were simulated having depth around 14–14.5 m. Different blast design parameters and respective blast-induced ground vibration have also been measured at the experimental site. The core samples of the rock present at the experimental site have been used for the evaluation of geotechnical parameters. These geotechnical parameters were used in the simulation models. The volume of rock excavated along the free face has been calculated in each model by varying the burden. It has been found that the burden value can varies from 35 to 40 times blasthole diameter (3.6–4.1 m) to achieve a greater volume of rock along the free face for 102 mm blasthole diameter and rock of 35 MPa uniaxial compressive strength.

Dec 22, 2023

By John H. Bassarear

By 1968 Cyprus Pima was milling 38,000 tpd of copper ore using a conventional flowsheet consisting of three stages of crushing rod mills and ball mills. A 15,000 tpd expansion was put on stream late in 1971 using primary crushing, semiautogenous mills, and ball mills. Identical ore is treated in both concentrators. This paper shows the weight and life of each individual liner for each crusher and each mill over a four year period from 1974-1977. Power and media consumption are shown for the same period and a comparison is made between the two reduction methods.

Jan 1, 1980

By Amanda Powers, Brian Glynn, Robert Sauceda, Daniel Huffines, Mike Garbeth

This paper will review the evaluation performed for the Cottonwood & Hackberry Creek Wastewater Interceptor Improvements Project to replace two separate aging and undersized interceptor sewers by either open cut construction or trenchless construction methods. A case study will be discussed for the utilization of microtunneling to avoid a deep open cut excavation within a landscaped roadway median to construct nearly a mile of new 60-inch interceptor sewer in an urban area adjacent to an environmentally sensitive riverine area, while minimizing the permitting and environmental impacts of construction, and minimizing the impacts to residents and vehicular trafc and restoration reuirements.

Jun 23, 2024

By Robert D. Thomson

Land use is the single most important element affecting the quality of our physical environment. .The minerals industry is a user of land and by its very nature, directly affects the landscape. Mining is a very visible activity. Producers of sand and gravel, crushed stone, clay, cement and lime operate right at the interface of the public. These production sites must be located near population centers. People are more travel oriented than years ago and through use of the expanded interstate highway system visit remote and little-visited areas. They visit communities on their vacations, places they enjoy on weekends and places they drive past on business trips. Although not residents of these localities, they have a strong interest in changes that occur in the landscape. As a result, the public has a greater concern today about mining and its use of land. From 1930 through 1971, the minerals industry used 3.65 million acres, or 0.16 percent of the land mass in the United States (4)2/. Of the total 3.65 million acres utilized, about 59 percent was accounted for by the area of excavation, 20 percent by disposal of overburden and other mine wastes from surface mining, 13 percent by disposal of mill or processing wastes, and 5 percent by disposal of underground mine wastes; the remaining 3 percent was subsided or disturbed as a result of underground workings. Nonmetallic minerals and fossil fuels each accounted for 43 percent of surface land used during 1930-71; the metal mining industry utilized the remaining 14 percent.

Jan 1, 1976

By J. K. Ahlness

The Bureau of Mines investigated technologies for determining the integrity of in situ leach mining wells. A self-contained trailer-mounted well integrity testing system (WITS) was designed and built to enable rapid testing of well casings for leaks as required by environmental regulations. The WITS utilizes two inflatable packers to seal off the entire casing length or any portion thereof. Water pressure is built between the packers to the desired test pressure, and the presence or absence of casing leaks is determined by monitoring the pressure drop between the packers. A winch and steel cable are used to run the packers in and out of the well. The WITS underwent an industry field test at the Irigaray in situ uranium leaching mine near Buffalo, WY. A total of 37 wells with an average depth of 225 ft (69 m) were tested at an average rate of four wells per 8-h shift with a two-person operating crew. This represents a 75-pct time savings and an 83-pct labor savings compared to the rigid-pipe method previously used at the mine, with which a three-person crew tested an average of one well per shift.

Jan 1, 1986

By Steven K. Ruggieri

Increased coal production on longwalls has brought with it higher levels of dust generation. Most U.S. longwall mining operators have difficulty complying with Federal dust standards, which are stricter than European standards. Longwall operators faced with a longwall that is "out of compliance" have implemented a variety of practices designed to reduce dust levels. Mining conditions and other important variables, however, can cause fluctuations in dust levels that may overshadow the performance of a new dust control technique. This can result in the continued use of an ineffective technique or lead to the abandonment of an effective dust control technique. No single technique can keep a longwall in compliance. Maintaining compliance requires a fundamental approach to dust control -- proper application and continued use of effective dust control techniques.

Jan 1, 1983

By S. P. Brown, J. E. Worthington

Increasingly, exploration geology seems to be growing into a practice overly separated from production geology, yet the eventual purpose of exploration is a producing mine. To help in the search for new deposits, exploration "lessons" will be drawn from the papers given at the Fall AIME Applied Geology Symposium. In addition, examples will be re-emphasized to show how early observation of matters now routine to mine work (for example, hydrology, rock mechanics, oxidation state) can help increase the effectiveness of exploration.

Jan 1, 1992

By W. R. McDonald

The U.S. Department of the Interior, Bureau of Mines, conducted field tests on acidic copper tailing as part of its program to devise, improve, and demonstrate technology for stabilizing mining and mineral processing wastes. Results will be presented from successful 1/8-acre and 1-1/2-acre demonstration revegetation plots established in 1973 and 1974 on an abandoned copper tailing pond located on public land adjacent to Holden Village, Wash. The tailing was neutralized with treatments of either dolomitic lime or limerock and fertilized with processed sewage sludge and/or commercial fertilizer. Plant growth covering 60 percent of the surface was achieved on both test plots. Regar brome, Tegmar intermediate wheatgrass, and tall wheatgrass provided the best plant growth and surface coverage. In neutralizing the tailing, the target pH of 6.8 was not achieved; however, good plant growth occurred in areas where the pH ranged from 2.9 to 5.8.

Jan 1, 1979

By Immo H. Redeker

The Kings Mountain area of North Carolina is the lithium pegmatite center of the U.S., if not of the whole world. We have two spodumene and by-product mineral producing companies, Lithium Corp. of America, and Foote Mineral Company. We also have Kings Mountain Mica and Kings Mountain Silica Companies producing mica. feldspar, quartz and clay from weathered pegmatites in that area. Figure 1 gives the location of the spodumene pegmatite area in North Carolina. The two spodumene producers mine typical pegmatite ore in open pits after removing amphibolite or mica schist overburden which is sold to aggregate producers. The ore reserves are discussed elsewhere in this session. They are in the order of plus 50 million tons but not unlimited. 1.2 The major minerals found and concentrated from the North Carolina spodumene pegmatite ores are tabulated on Table 1.

Jan 1, 1977

By B. W. Stunkard

Hibbing Taconite Company is located by the cities of Hibbing and chisholm near the center of the Mesabi Range, approximately 169 km (105 miles) from the Canadian Border. The plant site is equidistant from these two communities, about 6.4 km (4 miles) from each. A 169 km (105 mile) railroad connects us with the port of Superior, Wisconsin, where the pellet production is loaded into lake carriers for lower lakes destinations. Immediately to the south of the mine area is the world famous Hull- Rust-Mahoning Mine which produced more than 700 000 000 million tons of red ore between the years 1893 and 1973.

Jan 1, 1979

By Ryan C. Stephan, Zach Agioutantis, Christopher Mark

During the past 15 years, roof fall rates have fallen dramatically in US coal mines, particularly in regions where the roof is weakest. The remarkable reduction in the number of roof falls has been accomplished with more effective roof support systems. The purpose of this paper is to present a design methodology that builds on and quantifies the basic roof support concepts that have been successful in the USA. The methodology starts by defining three modes of roof support, based on the roof strength relative to the stress level: (1) suspension, where roof bolts mainly provide skin control for strong roof; (2) beam building, where moderate strength roof can be supported by roof bolts alone; and (3) supplemental support for weak roof. Next, a large database of roof fall histories at a number of mines is used to define the approximate boundaries of these three regimes based on the coal mine roof rating and the depth of cover. Finally, guidelines are presented for site-specific design of support systems within each regime. The new computer package, analysis of mine roof support (AMRS), implements the design methodology.

Sep 29, 2020

By Cory Dippold, Michael Mett, Jérôme Steinkühler, Kristi Latimer

For decades, tunnels of all types have been a significant part of our infrastructure. In particular, water tunnels carry millions of gallons of fresh water every day to major metropolitan areas and surrounding communities. As a critical piece of public health infrastructure, it is important to inspect the condition of these tunnels regularly to ensure reliable and continuous operation. A specific challenge with water infrastructure is that it’s often difficult or impossible to shut down the system for long periods of time to perform the needed inspections. The latest method of tunnel condition assessment is the use of hybrid reality 3-D scan data. Photogrammetric and LiDAR based 3-D data ensure a reliable and objective view of tunnel conditions. The data can be used to support a detailed digital inspection including the compilation of databases that consist of a wide variety of deficiencies such as cracks and spalls within the structure. Mott MacDonald, a design engineer company worked closely with Dibit, used a 360-degree scanning system to collect high-resolution photogrammetric and LiDAR data on a recent project involving a water tunnel. The allows for full 360-degree coverage of the tunnel surface including a water covered invert. It operates at walking speed and ensures a fast and reliable data acquisition which can reduce the time of tunnel shutdowns. Several allocated inspection weeks can reduce to few days, with the final work product being a higher quality and more complete deliverable than traditional inspection methods would have provided. The true-color 3D-model has a photo resolution of 1 × 1 mm (0.039 × 0.039 inches) which makes cracks visible with a width of down to 0.3 mm (0.011 inches). The assessment of water tunnels, its technical challenges and the results of the 3D-tunnel inspection case study are illustrated and described in this publication.

Dec 1, 2022

By K. Burke, K. L. Myers, R. Espell

Barrick's Goldstrike AA heap leach pad is an HDPE-lined facility that was used for gold recovery from low-grade ores using conventional cyanide heap-leach technology. The pad was operated from 1987 through 1999. Goldstrike prepared a unique reclamation plan for the AA leach pad facility to provide for a cost-effective, environmentally sound facility closure and to fulfill the State of Nevada's closure requirements. The traditional Nevada leach pad closure procedure involves rinsing to reduce the cyanide concentration to an acceptable level followed by reclamation. However, rinsing does not typically reduce certain metals and compounds, and some constituents may increase in concentration with rinsing. A closure scenario to effect limited infiltration through installation of a capillary cover for the leach pad was developed. The capillary cover was constructed by placing a fine-grained layer above the coarse-grained spent leach material to create a capillary break. In an arid climate such as in Nevada, the fine-grained layer will rarely reach saturation, and the cover will be able to store water during precipitation events and will allow removal of water through evaporation and transpiration (ET) during the growing season. A 1.22-m (4 ft) cover thickness was selected as the optimum design cover thickness. The drainage network on the surface of the recontoured AA heap leach pad was specifically designed to enhance the re vegetation, reclamation and sediment yield control aspects of the AA heap leach pad closure, while resulting in a natural looking surface that is compatible with the surrounding topography. Adjacent natural topographic features were used to establish target design parameters for recontouring and erosion-control design.

Jan 1, 2002

The reduced need for traditionally trained and educated personnel in the mining industry is systemic to the changing mining industry. Our universities and other training institutions are doing just fine meeting the traditional skill needs required by the industry. But are the skill needs going to be the same in the near future? The answer may be NO!! Mining is changing: increased liabilities and costs of environmental and safety issues; lower grades of minerals in traditional mining activities; the advent of new bio-chemical processes and robotic equipment as more productive and economic alternatives; and, larger more sophisticated and automatic equipment. Engineering is more specific, accurate, precise and expensive. Measurement is more thorough and timely of progress, production, costs, and productivity. And we will be engaging in more undersea mining, possibly space bases processing, less human interaction, and more remote control of events than was ever thought possible in the past. This paper presents several of the systemic changes that are presently and will continue to change the face of mining. It will identify area where education and management will have to address these changes.

Jan 1, 2011