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By J. H. East, D. Harrington

"INTRODUCTION Shaft mines, coal and noncoal alike, have a common hoisting problem that remains largely unsolved - how to obtain a mechanical device that will suspend a cage or skip in a mine shaft if the hoisting rope should break or become detached from the cage or skip and that will function effectively under all conditions of service. Safety catches, or safety dogs, as they are commonly named, are installed on nearly all mine cages and many skips operating in American mines, but often, if the hoisting rope breaks, the cage or skip falls to the bottom of the shaft in spite of safety devices, causing much property damage and often fatalities.Available information relative to safety catches for mine cages and skips, desirable characteristics of safety catches and methods of testing safety catches to determine whether they are functioning correctly has been assembled in this publication for the convenience of those responsible for the safe operation of mine cages end skips and, more particularly, to focus attention on the need for a device that actually will stop and suspend a falling cage or skip under all conditions of use and do it without killing or maiming the occupants."

Feb 1, 1948

By Gordon Miner

GENERAL DESCRIPTION At the Star mine, Hecla Mining Co., located in Burke, Shoshone County, ID, the mining method is horizontal slicing (timbered or untimbered) cut-and-fill using hydraulic sand backfill. Back stoping as well as breast stoping is used; see Fig. 1. The annual produc¬tion from all cut-and-fill mining is 259 816 t (286,400 st). The average depth ranges from 366 to 2408 m (1200 to 7900 ft). A majority of the tonnage comes from an average depth of 2240 m (7350 ft). Average travel time to the stope is 1 hr. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size and Ground Conditions The ore body is 610 to 1219 m (2000 to 4000 ft) along the strike and 2408 m (7900 ft) on the dip, with an average vein width of 2.6 m (8.5 ft). The dip is essentially vertical. The ore body is heavily sheared and broken on the main fault structures; it is more competent on the wall veins but everywhere subject to rock bursting at depth. The hanging and footwalls are strongly fractured on the main fault structures, again more competent but still fractured on the wall veins. All host rock is Revett quartzite. Value and Production Requirements The ore value is $56 per ton. Production require¬ments are 1089 t/ d (1200 stpd), five days per week. Why Cut-and-Fill? The slusher extraction method is the most satisfac¬tory and practical for narrow vertical veins with sheared walls. The method must be quite selective to be com¬mercial. The veins are too narrow for rubber-tired ex¬traction and the grade is not high enough to make resuing practical. DETAILED DESCRIPTION Development Access to the main shaft is by the 3.2-km (2-mile) main haulage tunnel. The level intervals in the vertical timbered shafts are 61 m (200 ft). Vein development is by crosscut and laterals located 30.5 m (100 ft) into the vein wall. Vein crosscuts are on ±61 m (200 ft) centers. Access to the vein is by raises carried up with the stope. The raises are equipped with four wood¬cribbed chutes (two orepasses reinforced with angle irons, one manway, and one timber slide, Figs. 2-6). The initial cut is located 6.7 m (22 ft) above the main level (Fig. 1). Stoping Cycle Detail Sampling: Grab samples are taken from the mine cars. Channel sampling of the faces and backs is done when necessary. Drilling: For stope drilling, Ingersoll-Rand 300M percussion drills are used, with Ingersoll-Rand 300M and Gardner-Denver RB83M stopers, used for back stoping. Breasting down is done with Gardner-Denver S83FM jacklegs. The back stoping rounds are 0.9 to 1.8 m (3 to 6 ft) and the breast stoping rounds 1.5 to 3m (5 to 10 ft). Blasting: For stope blasting DuPont Tovex 100 watergel with fuses and igniter cord is used primarily. Approximately 60% of the blasting is done with am¬monium nitrate-fuel oil (ANFO). For development headings and shaft sinking, DuPont Drivex watergel with Ensign Bickford Nonel Primadet primers is is used. Mucking: Broken ore is removed entirely by slusher in the stopes. These are mostly 3.7-7.5-kW (5-10-hp) Ingersoll-Rand air-powered or 7.5-37.3-kW (10-50-hp) Ingersoll-Rand electric-powered. In the horizontal de¬velopment headings Eimco 12B and 21 and Atlas Copco LM-56 overshot mucking machines and a 0.76 (1 cu yd) hydroelectric Wagner HST-1 LHD (load-haul-dump) unit are used. Rockway for Extraction: The cribbed chutes (Fig. 7) are nearly vertical and hexagonal in shape and are made of spaced 152 x 203-mm (6 x 8-in.) timber, reinforced with varying weights and sizes of angle iron, depending on wear requirements. Rectangular cribbed chutes are used where ground pressure is not a problem. Cribbing is added in 2.4 or 3-m (8 or 10-ft) extensions accord¬ing to the floor height (whether timbered or untimbered). See Figs. 8 and 9. Backfilling: Backfilling is done with hydraulic sand consisting of classified mill tailings at 65% solids. The fill contains approximately 20% 325-mesh fines. The tailings are pumped 3353 m (11,000 ft) at 50-55% solids 22.7 dry t/h (25 dry stph) with a duplex piston pump. Cycloning increases the tailings density to 65% solids. Fill storage is in a 998-dry-t (1100 dry st) agi

Jan 1, 1982

By Yi-Shen Li

This report has been prepared by Lockheed Missiles & Space Company, Inc. (LMSC), under United States Bureau of Mines Contract No. H0220040 dated 21 June 1972 for the design, development, fabrication, and certification of the One-Hour Self-Rescue Breathing Apparatus (PBA). The PBA is a self-contained, oxygen-generating, CO2-removing closed-loop breathing apparatus that provides a minimum of 1 hour of breathable atmosphere during escape from a mine with a contaminated or oxygen-deficient atmosphere. This Cost-Plus-Fixed-Fee (CPFF) contract has been successfully completed in a three-phase program. The Phase I tasks included the design, development, and fabrication of prototype units developed at LMSC in accordance with the requirement of the Code of Federal Regulations (CFR) Title 30, Chapter 1, Subchapter B, Part 11 (Appendix A), and was submitted to the National Institute for Occupational Safety and Health (NIOSH) for joint NIOSH and Bureau of Mines certification testing.

Jan 1, 1974

By James F. Archibald, H. Jame Hackwood

"Research was performed to assess the feasibility of barrier membrane substances, for use within mining or associated high risk environments, in restricting the diffusion transport of radon gas. Specific tests were conducted, both within laboratory and in situ environments, to determine radon gas concentration ratios across a barrier of interest and emanation rate variation resulting from application of such materials. Several materials have been demonstrated to be effective in restricting the emanation of radon gas into initially radon-free environments. One liquid material shows particularly good promise upon consideration of ideal radon barrier criteria.IntroductionIt has long been known (I.2.3) that inhalation of the short-lived, alpha particle-emitting daughters of radon gas can result in irradiation of lung tissue with the potential for causing lung cancer. Control measures are necessary to maintain concentrations of airborne contamination at a minimum to protect miner health and safety. Typical control practices in mines have been through the application of systematic ventilation and backfilling of excavated opening. As mines become deeper, however, and additional workings become exposed, increased ventilation capacity requirements are needed. As an alternative to other radiation control measures, the use of sealants to prevent radon migration from walls into mine atmospheres may provide a suitable engineering alternative."

Jan 1, 1987

By Richard G. Stearns

Extensive thick lignite apparently lies within 250 feet of the land surface in Dyer, Lake, Lauderdale, Obion and Tipton counties. Information on geology, land use, soils, groundwater and instability is compiled, along with a bibliography. A test and monitoring site was investigated at Fort Pillow Prison in Lauderdale County. Analyses were made of lignite, overburden, associated water and leachate. Lignite has high BTU (about 7800) and low sulfur (1.1% avg.). A year or more of data are presented on rainfall, water levels, and chemistry of surface water, groundwater, leachate and water from test pits. Main potential environmental problems are quality of surface water, and possibly shallow groundwater. The main aquifer of the region will likely be un-affected by mining. Low transmissibility of shallow aquifers will minimize lowering water levels of wells. Soil reclamation and conservation should be readily accomplished, Dangerous earthquakes have a low probability and mines are not significantly more hazardous than steep bluffs.

Jan 1, 1981

During the last 20 years, more than 80 km (50 miles) of tunnels have been constructed in the Los Angeles, CA area. Recent projects include The East Central Interceptor Sewer (ECIS), completed in 2004. It spans more than 18 km (11 miles). The Northeast Interceptor Sewer (NEIS), completed in 2005, spans 11 km (7 miles). And the 2-km (1.3-mile) Metropolitan Transportation Authority?s Gold Line Eastside Extension (MCGLEE) was completed in 2006. All of the tunnel routes lay beneath heavily populated urban environments so minimizing ground surface settlement was critical to the success of the projects. Previous tunneling efforts in the Los Angeles area using open shield methods resulted in significant settlement that damaged roads, utilities, buildings and other structures. Earth pressure balance (EPB), or slurry machines, were specified for these projects to reduce subsidence risk. The contractors chose EPB tunnel boring machines (TBM) for the work. The closed and pressured face of the EPB TBM reduces loss of ground at the tunnel face and, when the machines are used in combination with gasketed pre-cast tunnel liners and backfill grout behind the installed segments, losses from over-cut of the excavated surface are also reduced.

Jan 1, 2008

By P. Desclaux, A. Gosselin

"In 1999, PFC measurements were carried out at Alcan smelters as part of a large measurement campaign led by the Canadian Aluminium Association. Side worked prebake (SWPB) and horizontal stud Söderberg (HSS) plants in Arvida were the selected sites. CF4 and C2F6 emissions were measured continuously in the exhaust duct and at the roof vents for a week. In parallel, voltages from four designated cells were recorded at a high scan rate. Results were analyzed and correlations between voltage, anode effect duration and PFC emissions were tested. Some fundamental anode effect mechanisms were proposed and validated with the observations. IntroductionFollowing the international agreement reached within the scope of the Kyoto protocol, voluntary partnerships have been established in many countries especially for the aluminum industry. It is well known that the PFCs that are periodically emitted during aluminum production are the major source of fluorocarbon emissions. The latter are part of the greenhouse gases. In the fall of 1999, Alcan announced that it will adopt, promote and regularly renew a long-term greenhouse gas management commitment at all of its facilities within the framework of the so-called TARGET program that was implemented during 2001. The program is intended to produce on-going reductions, which will be reported publicly on an annual basis.Improvements in the understanding of the mechanisms leading to PFC emissions will contribute to targeting the most appropriate reduction actions. PFC measurement campaigns have been driven toward this end. The first measurement campaign was conducted in 1993 in order to get a picture of the emissions and a base line. The last measurement campaign was conducted in 1999 and its main objective was to compare current emissions with those measured in 1993 and to confirm the accuracy of the predictive equations for the calculation of PFC emissions. This campaign has been conducted by the Canadian Aluminium Association and measurements were made in plants using different technologies. Results of this campaign have already been reported by Bouchard et al. (2001)."

Jan 1, 2002

By R. England

"This paper describes the objectives and design parameters for the operation of a computerized In-The-Hole (I. T.H.) Drill. The principal objective is to add computer control to an Inco 00-60 I. T.H. (CMS-CD-90) drill in order to drill holes with greater accuracy. The computer provides control of the angle of the hole by maintaining the orientation of the drill head, and optimizes the straightness of the hole by maintaining a constant force on the drill bit.The second objective is to provide the greatest degree of operational automation, so the objective outlined above can be accomplished with a minimum of operator intervention.In order to provide full operational automation it was necessary to also provide the capability for the computer to add and remove drill rods. To accomplish this, a rod-handling mechanism consisting of a rod storage rack and rod manipulator arms was used.IntroductionMining machinery that lacks automatic control has been found to show a high degree of variation in work output and performance quality when operated by different personnel. Differences in operator attitude, judgment, and skill are reflected directly by production statistics. The addition of automated control has the potential for considerable improvement in machine life and performance. Even with a more acceptable mine environment and much safer conditions than ever before, situations still exist where it is preferable to remove personnel for reasons of safety as well as productivity. Typical advantages of such situations are automated skip loading and hoisting, and the use of remote control load-haul-dump units exposed to open stopes.Other cases arise where heavy work is required under conditions where lighting is poor, floors are slippery, noise levels are high and dust and oil mist exist in the atmosphere. I.T.H. drilling is carried out under such conditions and is one operation where automation can easily be justified."

Jan 1, 1987

By David E. Thompson

This paper describes the full-scale field load testing of three deep foundation units using the Osterberg Load Cell. The load tests were completed on three separate projects, two in Massachusetts and one in New York. The Massachusetts projects involved the load testing of two 18-inch O.D. concrete-filled steel pipe piles over water for railroad bridge reconstruction projects in Revere and Saugus/Lynn. The New York project involved the load testing of a 24-inch diameter drilled shaft socketed into sandstone on land for a building foundation in Rochester. The 18-inch O.D. piles were loaded to failure at jack pressures of 142 to 215 tons. The drilled shaft was loaded to failure at jack pressures of approximately 450 tons. The loading testing procedure is described and the results of the three tests are presented. The advantages and disadvantages of the Osterberg load cell for load testing of deep foundations are discussed.

Jan 1, 1989

By S. R. Droes

The U.S. Bureau of Mines investigated calcium fluoride (CaF2) assisted sulfuric acid (H2S04) leaching as an alternative to the melting-quenching procedure to obtain Mn from domestic manganese silicate resources. Pyroxmangite [(Mn, Fe) Si03] ore containing, in percent, 34.4 Mn, 22.8 Si, 2.6 Ca, and 1.3 Fe was leached in a 500-mL resin kettle. Ninety-six percent of the Mn was extracted under conditions of 330 g/L ore, 245 g/L H2S04, 35 g/L CaF2, 90' C, and 2 h. To incorporate electrowinning in recovering Mn, the ore was leached with a simulated spent anolyte solution containing, in grams per liter, 12 Mn, 140 H2S04, 130 (NH4)2S04 (ammonium sulfate), and 5 CaF2. Manganese extraction of 92 pct was achieved from 130 giL ore leached at 90° C in 3 h. The Fe, silica (SiOJ, and other impurities were precipitated from the pregnant solution by neutralization with ammonia (NH3). Manganese of greater than 99-pct purity was deposited at a cathode current density of 50 mA/ cm2 at 30° C, with a current efficiency of 65 pet in a two-compartment cell. A flowsheet was proposed for the leaching and electrowinning procedure.

Jan 1, 1990

By S. R. Zimmerley

[In the course of a flotation investi£ation, a siliceous gold ore was ground in a'ball mill to ':1inns 300-meeh. It wa. found that the small amotIDt of _Ius 300-mesh material had a gole.. assay approximately twice that of the oriGinal ore, &~d that this overs.ize nroduct also contained much abrac..ed iron. .,Joreove I the gold assay of the abraded iron t which was !1epnrated ma§metically', ~iVFl.£ eight ti;nes that of the are. These facts suggested that some r31aticnship ex?...,ted between the abnorma11y high gold content an the prese:1ce of brA-cit)" iron. It was decided, therefore, to investigate furt~er th~ Fl.Gsociation of the bold ~ith the iron abraded from the balls during sri~Qing ]

Jan 1, 1937

By Lennart Mukka

The Kiruna Mine in Sweden currently has three ventilation systems. The first two (a new and old system) serve the production areas. The third system is used for the facilities on the former main haulage level 775. That area includes offices and workshops for load haul dumpers (LHD) and drill rigs. The third ventilation system also covers the crushing and haulage on level 1045. At the present time, the total airflow for the mine is 1,600 m3/sec(3.4 million cfm). The current system serves the levels above the 775 level. The new one is for the levels between 775 and 1,085 m (2,540 and 3,560 ft), which are needed for the new ore body. When all of the production is below level 775, the old ventilation system will be closed down.

Jan 1, 2002

By David Stephenson, Hugo Granados, Steven Klohn

"HudBay’s Constancia project is a copper molybdenum concentrator located in southern Peru. In 2010 Ausenco was contracted to perform a feasibility study optimization review which resulted in an improved design with significantly increased throughput capacity at a minimal increase in capital cost. Construction began in 2012 with commercial operation commencing in May 2015. This paper outlines the process plant design as well as describing the plant’s major equipment selections, start-up and early operations experiences.IntroductionHudBay Mineral’s Constancia project is located at 4200 meters above sea level (masl) in southern Peru, approximately 630 km south-east of Lima, Peru. The property can be accessed by road from Cusco, Peru, (approximately 110 km to the north), or from Arequipa, Peru (approximately 215 km to the south). Matarani, accessed via Arequipa, is the closest port.Constancia is located within the Yauri-Andahuaylas metallogenic belt. The region contains several large copper-gold-molybdenum porphyry deposits such as Antapaccay (by Glencore) and Los Chancas (by Grupo Mexico), and copper skarn deposits such as Tintaya (by Glencore) and Las Bambas (by MMG). Constancia’s ore reserves contain copper and molybdenum with trace amounts of gold and silver.Ore is mined by an open-pit operation. The process plant recovers copper and molybdenum concentrates, storing tailings in a conventional tailings management facility. Infrastructure at the site includes a grid power supply (via a 70 km overhead transmission line from Tintaya), water supply, workshops and an accommodation camp. Mine life is 22 years.Site construction works began in 2012 with first copper concentrate produced in late 2014. The project was executed for approximately 1.75B$USD.Ausenco’s design approach focussed on developing a capital efficient copper molybdenum concentrator. This paper outlines key features incorporated in the concentrator design, plant layout and equipment selection, as well as start-up experiences and early operational results."

Jan 1, 2016

By Enver Alan, MerkeziYapı

People are migrating because of economic, social, natural and political reasons. These natural and humane factors effects the distribution of populations. The need for tunnels has grown in order to provide a comfortable life and reduce losses such as waste of time, labor, energy, efficiency and so on. It is inevitable to carry out excavations in rock tunnels (shears, platforms, lines, connections, wastewater, distribution, energy, transportation etc.), that will be built by excavating with conventional method, by controlled blasting regarding with constrains. In this study of applied explosives engineering the blasting applications are evaluated, which were carried out for research and development purposes at Yenisahra Station tunnels in Kartal Formation which was built with the aim of solving İstanbul's transportation problem within the framework of the Kadıköy-Kartal Metro Project. Twenty-four shots were made by using explosives in 60 blastholes that were drilled in the tunnel faces, which were located between and outside of two different faults. Six microphones were used to measure the air shock and eight geophones were used to measure the parameter values of the vibrations (particle velocity, frequency, displacement, acceleration, amplitude, wavelength etc.), which were placed at predetermined points of the surface, occurred during the blasting applications. Data from the geophone and microphones were recorded on six seismographs. The coordinates and the distances between the shot points and the measurement stations are determined by an electronic theodolite. The total number of seismic records, recorded in seismographs, is 118. The number of records of vibrations that crossed the faults is 42 and the number of records of vibrations that did not cross the fault is 76. The particle velocity, frequency, amplitude, acceleration, displacement and wavelength were measured in transverse, longitudinal and vertical directions. The total number of measurements is 354. By evaluating all seismic records, the effect of delay intervals, faults and scaled distances on the particle velocity, frequency, amplitude, displacement, acceleration, wavelength and air shock were investigated. When the vibrations formed during the Research & Development (R&D) blasts were examined, it was determined that the parameter values of vibrations that crossed the faults are lower than the ones that did not cross the faults. In addition, when the particle velocity values of all vibrations are examined according to the present circumstances, it is determined that the waves did not cross the fault in all delay intervals are superposed in all directions, and that the least superposing occurred in the 50 ms delay range.

By Pier Francesco Paglini, Gian Luca Menchini, Pier Francesco Boschi

"PROJECTThe “Caltanissetta” Tunnel is part of the ANAS S.p.A (National Autonomous Roads Corporation) $ 1.3 Billion Highway 640 Caltanissetta-Agrigento (Sicily, Italy) Rehabilitation Project, consisting in upgrading of 62 km (40 miles) of highway. The Italian multinational construction company Cooperativa Muratori & Cementisti di Ravenna, is the General Contractor for the design and build contract. The highway S.S. 640 starts from Porto Empedocle, to the intersection with the Motorway A 19 Catania-Palermo.The entire project, double carriageway designed for speed 70-120 km/h and maximum longitudinal slope of 4.2%, is divided into two sections. First Section: just finished and opened to traffic. Second Section: mainly involving the province of Caltanissetta, length about 28 km (18 miles), works started in 2013. This second section includes the most challenging work of all the project, the “Caltanissetta” tunnel consisting of two separate tubes, each with 3.9 km length and inside diameter of 13.50 m, in order to host 2 traffic lines and an emergency line. HORIZONTAL AND VERTICAL ALIGNMENT - GEOLOGY AND HYDROGEOLOGYThe plan alignment of “Caltanissetta” tunnel is formed by two tubes which are located at a minimum mutual distance of 22 m to a maximum of 63 m, with n. 9 pedestrian and n. 4 road cross passages; ventilation shafts are not provided. Overburden over portals area is about 5 m till a maximum of 120 m. Tunnel sections have variable longitudinal slope from 2.6% to 0.5%, transversal slope of about 3.5%. Right tube length is 3,992 m, left tube length is 3,877 m."

Jan 1, 2016

By Allen Chung, John Twomey, Christopher J. Greet

"It is widely accepted that the type of grinding media has an impact on the grinding chemistry and subsequent flotation behaviour of the sulphide minerals being separated. There are countless laboratory investigations demonstrating that inert grinding media produces more oxidising pulp potentials, reduced levels of grinding media corrosion products and superior concentrate grades and valuable metal recoveries. However, taking these results to industrial scale has proven difficult.Work conducted at the Ernest Henry Mine, in north western Queensland, Australia, at laboratory and pilot plant scale clearly indicated that using a high chrome grinding media resulted in significant improvements in both copper and gold recoveries. However, advancing this work to plant trial represented considerable financial and technical risk to the mine.This paper provides details of the protocol developed and used during the high chrome grinding media plant trial. It describes the test regime employed to measure changes in pulp chemistry, and the statistical methodology utilised to interpret the results. The work also highlighted the need for close cooperation between the metallurgists on site and the researchers conducting the trial.To date, the trial has produced excellent results: indicating that the copper recovery has improved by about 2 percent. The successful application of high chrome grinding media to the Ernest Henry ore has increased metal value by $18.7 million USD per annum based on current spot price for copper.INTRODUCTIONTheoryThe application of electrochemically inert grinding media to mineral systems has been extensively studied (Table 1). Broadly, these studies indicate that most sulphide minerals are more noble than the grinding media used during comminution. Therefore, the sulphide minerals are cathodic with respect to the forged steel grinding media, and the following reactions apply:"

Jan 1, 2011

By Gregory J. Chekan

This Bureau of Mines report presents three methods for designing bulkheads to impound water underground: (1) thin and thick plate design; (2) South African plug design; and (3) single and double bulkhead seal design. Related areas critical to the long-term effectiveness of underground water impoundments are also addressed. These include bulk-head anchorage, concrete specifications and placement, the grouting of permeable strata, and the sizing of barrier pillars. A case study involving hydrostatic tests conducted on a single bulkhead seal constructed in the Safety Research Coal Mine of the Bureau's Pittsburgh Research Center is presented in an appendix.

Jan 1, 1985

By Shuie Li, Taibai Li, Tao Hu, Zhongjie Wang, Xiang Ge

As one of the main power sources, lithium-ion batteries (LIBs) will continue to be applied on a large scale in the future market. Commercialized LIBs cathode materials contain various valuable metal elements including Li, Co, and Ni. The development of green and efficient recycling technology is essential. Deep eutectic solvents (DESs) have recently emerged as a new class of green solvents that could potentially be applied for the LIBs recycling industry due to their capability to leach the active materials without the introduction of environmentally hazardous reagents as used in conventional hydrometallurgy process. Considering the rapid progress, a critical review focusing on the progress and fundamentals about the overall efficiency has practical significance for the further advancement of this field. Herein, we briefly introduce the overall process of using DESs for LIBs recycling and specifically focus on the efficiency of each step. Current fundamental understandings and new experimental approaches to enhance the efficiency of the leaching process, the extraction process, and reusability are summarized. We expect this review article to inspire scientists to use DESs as powerful tools for advancing the frontiers of LIBs recycling.

Jul 30, 2022

By Clyde Sitterud

Presentation Agenda ?Global Mining Tire Demand ?What is driving it? ?Latest Situation ?How long it will last? ?Michelin?s Response to Increase Supply ?New plant ?Additional presses ?Recommendations for Mining Users ?Treat tires as your major assets ?Areas of attention that will produce immediate results

Jan 1, 2005

By D. Harrington

United States newspapers of 25 or 30 Years ago ran headlines every few weeks telling of some mine disaster. Each disaster was a first-page attraction for a day or so then was forgotten until the next sensational event, frequently another mine disaster, a few weeks later. Interspersed with the large mine disasters were the so-called ?snipping? mine accidents that caused the death of one or two mine workers. The summation of mine fatalities of all types usually exceeded 3,000 a year, and nonfatal accidents to workers in mines of the country approximated 250,000 annually. From 1906 to 1910, inclusive, there were 84 major explosion disasters (about 17 per year) in. United States coal mines. The resulting fatalities totaled 2,388 for the 5-Year period. These frightful catastrophes helped the number of fatalities in coal mines of the country to reach the enormous total of 13,288 for the 5 years, or an average of 2,658 per year.

Jan 1, 1940