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By G. B. Clark

One portion of this project was to test a blast shield and to design some features for a novel tunneling method termed the Automated Drill and Blast System (ADBS). The ADBS tunneling concept was developed for the design of an excavation system of greater efficiency than conventional drill, blast, and muck (DBM) systems by minimizing the down time and approaching the non-cyclic efficiency of continuous tunneling by means of small charge blasting. Small charge blasting uses simultaneously detonated, small light charges (less than 200 grams per hole) in four to eight shallow (24 to 36 in. deep) holes usually in a line. Limitation of the total explosive per blast reduced air blast overpressure, fly rock velocity, vibration, and noise. Thus, shielded equipment can remain at the face and a tunnel shield permits support personnel to work outby the shield at all times. The ADBS equipment will be composed of five components: (1) a chassis, upon which is mounted automated mucking equipment, and a frame which carries (2) the hydraulic drill(s), (3) load/blast system(s), and (4) control cab(s). The blast shield may have its own mounting. Ventilation, horizontal, and vertical alignment controls are incorporated in the system. The blast sheild, which protects personnel outby the advance equipment from air blast overpressure, fly rock, and gases, was tested with full scale small charge blasting. A blast shield was designed, fabricated, and tested under conditions anticipated for a working model. The shield was designed to expand to fit the tunnel shape, to seal itself to the tunnel periphery, and to contain air blast, fly rock, and gaseous explosion products. In addition, the shield, which was lined on the inby side with rubber belting, reduced the blast noise level outby the shield to 113 dBA or less, which is very near permissible levels. The test results show conclusively that the shield concept is viable. Based partially on the shield tests, a blast resistant control cab was designed to be located on the equipment chassis inby the blast shield to protect operators during blasting, and to contain all the controls necessary for system operation and safety. The economics of tunnel driving using the ADBS were compared with those of DBM. Four rock types, which determine advance rate, and four cost categories were examined. The results of this analysis are as follows: 1. ADBS advance rate is faster because equipment remains at the face and operation procedes semi-continuously. 2. ADBS bit and explosive cost (which accounts for 4%o of the total advance cost) is higher than for DBM. 3. ADBS equipment cost, on a per foot basis, is lower than for DBM. 4. Due to a reduced labor force, ADBS labor cost is lower than for DBM. 5. Because of the overbreak reduction due to controlled blasting, ADBS tunnel support cost is lower than for DBM. 6. On a per foot basis, total ADBS advance cost is from 17% to 20% lower than for DBM, depending on tunnel diameter and rock type. The small charge method greatly reduces ground vibration, increases personnel safety by limiting excessive fracture, and decreases tunnel support requirements by reducing overbreak. The overall analysis, tests, and results to date show that the Automated Drill and Blast System may be developed into a viable tunnel excavation method. The method also may be adapted to use in the mining of ore. For some types of mining operations, the cyclic nature of conventional drill and blast methods may not be a disadvantage, either where the drilling and mucking may proceed simultaneously or where the operations are carried out in adjacent working faces. The proposed method would find application where continuous methods of excavation are desirable.

Jan 1, 1979

By K. Thirumalai

This study forms a part of Bureau of Mines continuing research on thermal fragmentation of rocks. The potential of internal heating techniques for rock fragmentation is discussed. A concept of rock fragmentation with rapid inter¬nal heating of a localized inner volume of rock is advanced The energy required for rock fragmentation is made available by creating a required vol¬ume of localized heating. The fragmentation of rock using the proposed method is analyzed and qualitatively compared with the results of experiments with Charcoal granite, Dresser basalt, and Sioux Quartzite. High frequency dielec¬tric heating below 100 MHz is used in the study as an example to examine the working of the concept. The selection of operating conditions for the experi¬mental heating is explained. Fragmentation of Charcoal granite and Dresser basalt test rock blocks is achieved for localized heating below 550° C. The heated volume required for fragmentation is observed to be less than 2 percent of the test block volume and the electrical energy consumption is in the order of 3.5 to 6 5 kwhr/m3 The method offers a possibility for in situ fragmenta¬tion of rocks, favorable for internal heating. The method is highly dependent on rock properties governing internal heat generation The efficiency of dielectric heating in the experimental study is observed to increase with increasing dielectric loss of the rock material, ranging from about 10 percent in Sioux. Quartzite to about 50 percent in Dresses basalt

Jan 1, 1970

By Sam S. Taylor

The disposal of oil-field brines by injection into subsurface formations other than fresh-water-bearing strata is a positive method of eliminating the harmful effects of mineralized water on fresh-water supplies, vegetation, and aquatic and other animal life. The methods used most generally for the disposal of brines produced with oil are (1) impounding in evaporation ponds, (2) controlled diversion into surface streams, and (3) injection into subsurface formations. Various States recognize one or more of the methods as legally authorized procedure. As a general rule, impounding brine in ponds and solar evaporation have not been entirely successful, principally because of the large volumes handled; the porous nature of the soil, and the low rate of evaporation. Likewise, the diversion of brine into freshwater streams by controlled dilution has not proved satisfactory in some areas, especially in parts of Kansas and Oklahoma where the rainfall is relatively low, because it has been impossible to obtain enough fresh water for such dilution.

Jan 1, 1939

By George J. Carter

Data obtained from field and laboratory examinations were used by the Bureau of Mines to evaluate 82 silica deposits in the Pacific Northwest. A total of 94 field samples was taken from 64 deposits, and an additional 18 deposits were investigated that did not warrant sampling. Of the 37 deposits found to be of high quality, only 16 were large enough to be classified as industrial silica resources. Another 27 deposits did not meet quality requirements. Methods of simple low-cost beneficiation and rapid classification of a large number of samples were investigated in the laboratory. These tests indicated that high-intensity electromagnetic separation was equal or superior to either high-or low-intensity electrostatic separation. In general, the electromagnetic method gave higher recoveries and produced equal or better grade concentrates. A glass button method developed for estimating iron oxide content of silica samples proved to be highly satisfactory as a means of classifying field samples and evaluating beneficiation tests.

Jan 1, 1962

By David A. Hill

This volume contains a summary of the results of past analyses on U.S. Bureau of Mines Contract No. 80122061 which are relevant to electromagnetic location in mine rescue situations. The analytical results indicated that detection of a trapped miner equipped with a special transmitter is feasible in most situations. Location of the miner by surface measurements is also generally feasible within certain errors. The feasibility of miner detection and the accuracy of miner location have been examined theoretically for a wide variety of situations. Agreement with experimental results is generally good in cases where measurements are available. Personnel involved in the investigation include J.R. Wait (Principal Investigator), D.A. Hill (Co-Principal Investigator), K.P. Spies, A.Q. Howard, and Lana Slusher (Administrative Assistant).

Jan 1, 1974

By Eric E. Cather

A mineral survey of the Fisher Gulch RARE II area (A5299), Trinity County, California was conducted by the U.S. Bureau of Mines and U.S. Geological Survey. The Bureau of Mines was responsible for detailed examination of mines, prospects, and mineralized zones; the Geological Survey conducted geological, geochemical, and geophysical studies of the area. The area is underlain by the Salmon Hornblende Schist. Tonalite stocks 1.5 mi (2.8 km) to the east and northeast of the area intrude the schist and are closely associated with the nearby nines (Cox, 1967). The mines have quartz veins containing sulfides and gold in shears trending east to north past in the schist and tonalite (Hotz, 1972). Strewn and terrace gravel s occupy most of the drainages, many have yielded substantial quantities of gold.

Jan 1, 1981

By Michael S. Miller

In 1987 and 1988, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied the 3,100-acre Borah Peak Wilderness Study Area (10-047-004) and a 708-acre parcel adjacent to the north in order to evaluate their identified mineral resources. The study area is located in Custer County, ID, about 18 mi northwest from MacKay. The study area lies along the western foothills of the Lost River Range and is underlain by quartzite, sandstone, shale, argillite, dolostone, and limestone. The Lost River fault, a major active fault, lies along the length of the study area. Large alluvial fans spread out from valleys originating east of the study area.

Jan 1, 1989

By James M. Spear

The U.S. Bureau of Mines and the U.S. Geological Survey conducted a mineral survey of the Elk Creek RARE II area during the summer of 1981. The study area encompasses 18,900 acres [29.5 sq mi (7,680 ha)] along Elk Creek, 18 mi (30 km) southeast of Covello, California. No mineral resources were identified by the U.S. Bureau of Mines during this survey. Assay results of samples taken in this area indicate only trace amounts of manganese and chromium. No radioactive or fluorescent minerals were detected. No oil and gas, coal, or geothermal leases have been recorded for the study area.

Jan 1, 1982

This Bureau of Mines report concerns two subjects important in the application of electric power in mining systems. Electrical transients and their suppression are discussed, and several considerations are explored with regard to the use of explosionproof or other electrical enclosures.

Jan 1, 1979

By Wallace W. Roepke

The Bureau of Mines studied the cutting characteristics of point-attack bits to reduce airborne respirable dust and energy during cutting. Linear cutting of two coal types using four bit types at three depths of cut with three space-depth ratios was performed with a modified horizontal milling machine using an optical particle-size monitor for respirable dust sampling. The cutting action of one bit on a rotary hardhead mining machine was mathematically analyzed and compared with the results of the linear cutting test. Airborne respirable dust per unit mass cut (specific dust) was found to be a monotonically increasing function of specific energy. Specific dust and energy decrease with increasing depth of cut. The amount of nonairborne respirable dust was 100 to 1,000 times greater than the airborne dust. The plumb-bob bit produced the most airborne respirable dust and the highest specific energy of the four bits tested. Rotary cutting was a greater dust producer and energy consumer than linear cutting because of the constantly changing depth of cut, space-depth ratio, and attack angle of the bit relative to the horizontal bedding planes. A new cutting technique is proposed to minimize the existing problems of the rotary cutting machines by providing greater production, reduced dust, and minimized methane ignition potential at the face.

Jan 1, 1976

By Henry Kreisinger, John Blizard, B. J. CROSS, C. E. Augustine

This report gives the results of 26 tests of a four-pass Edgemoor boiler fired with powdered coal at the Lakeside station of the Milwaukee Electric Railway & Light Co. The tests were made by the fuel section of the Bureau of Mines in cooperation with the research department of the Combustion Engineering Corporation and the operating department of the Milwaukee Electric Railway & Light Co. The object of the tests was to determine the thermal efficiencies and capacities obtainable by burning powdered coal under large central-station boilers, and the possibility of operating such boilers continuously at high efficiency and capacity without destructive effect on the furnaces and without difficulties in refuse removal. In any system for burning pulverized coal the furnace is the most important part because, to justify the cost of pulverizing, the powdered coal must be burned with higher efficiency than coal fired with mechanical stokers. In other words, it is the furnace that by giving higher thermal efficiency must pay for the installation, maintenance, and operation of the pulverizing equipment. No matter how simple the apparatus for the preparation of pulverized coal may be, or how simple the pulverizing process, unless the furnace is so designed that it can be operated continuously with high thermal efficiency, the whole system is a failure. For high thermal efficiency the coal must be burned almost completely with low excess air. But low excess air and complete combustion give high furnace temperature, which in turn causes erosion of the furnace lining and fusion of the ash; and removal of the fused ash is difficult. The necessity of complete combustion with low excess air thus brings with it these two important problems in the design of a furnace for burning powdered coal: 1, Prevention of erosion of the furnace lining; 2, easy removal of refuse from the furnace. For the purpose of solving these problems, the boiler tested was equipped with a furnace having hollow walls, through which about 60 per cent of the air needed for combustion passed before it entered the furnace. By passing through the hollow walls, the air cooled the furnace lining and prevented excessive erosion. A water screen was placed in the furnace about 3 feet above the bottom to keep the refuse deposited at the bottom from fusing and to make its removal easy. The design of the furnace, water screen, and burners was based on the experience gained in the previous cooperative tests1 with a smaller furnace, experimental water screen, and burners at the Oneida Street station of the Milwaukee Electric Railway & Light Co. The boiler tested had 13,057 square feet of heating surface. It was one of eight boilers fired with powdered coal, and was designated as boiler No. 8. The Lakeside station is the largest central station in the world that burns powdered coal exclusively. The coal used in the first five tests came from Illinois. The fuel in the other tests -:vas a mixture of Illinois and Pittsburgh coals.

Jan 1, 1925

By W. C. Blanchard

Time Domain Reflectometry (TDR) is a remote sensing technique using active backscatter. This technique is applicable to the testing for faults and multiple partial faults on cable. The battery operated hardware developed on this con¬tract has tailored this technique for testing of mining equipment trailing electrical cables. The processing of-t-he back-scatter is accomplished using a microprocessor. The visual output from the hardware to the operator is; the type, magnitude and distance to the cable fault in a numerical format. This greatly simplifys the use of this techniques for the operator.

Jan 1, 1980

By G. M. Martinez

The Bureau of Mines has investigated methods for the recovery of byproduct heavy minerals from sand and gravel operations in Oregon and Washington. These heavy minerals are not currently recovered except for gold in a few areas. The recovery of byproduct heavy minerals would provide a domestic source of minerals presently imported, and a more efficient use of domestic resources would be accomplished. Samples from more than 40 locations were treated by gravity separation to yield heavy mineral concentrates (black sands). Magnetite, ilmenite, zircon, rutile, chromite, platinum-group minerals, radioactive minerals and gold were identified in the concentrates. Individual zircon, ilmenite, chromite; magnetite, and gold products were recovered from selected concentrates by low-and high-intensity magnetic, high-tension, and heavy-medium separation techniques. The recovery for the individual mineral products ranged from 67 to 95 pct.

Jan 1, 1981

This publication contains four papers presented at a seminar on mine subsidence control held in Pittsburgh, PA, on September 19, 1985. The seminar was designed to keep the mineral industry informed of new technology developed by the Bureau of Mines that permits reliable and accurate prediction of mine subsidence. The papers describe actual field studies undertaken by the Bureau to monitor surface subsidence over longwall panels. Topics discussed include the efects of subsidence on water table levels, the development of subsidence pre calculation methodology suitable for use with the specific lithological conditions of the Pittsburgh coalbed, an engineering comparison of technologies used in surveying for longwall mine subsidence, and a comparison of the process of subsidence over two different longwall panels.

Jan 1, 1985

By Richard S. Gaps

In 1983 the U.S. Bureau of Mines conducted a mineral survey of the Golden Valley Wilderness Study Area (WSA), CDCA-170. The 29,887 acre WSA, located in the western Mojave Desert near Ridgecrest, California, is underlain by pre-Tertiary plutonic rocks and volcanic and sedimentary rocks ranging in age from Miocene (?) or Lower Pliocene (?) through Pleistocene and Recent. No mines were operating in the WSA in 1983, nor is any mineral production known to have come from the WSA. Two mining claim blocks, portions of which are within the WSA, and seven isolated prospects, four inside the USA, were examined and sampled. No mineral resources were identified. Widespread propylitic alteration, with localized argillic and alunitic alteration, occurs along the southern boundary of the study area. Samples from claims and prospects within the altered zones are anomalous in gold, silver and arsenic, and some contain antimony, tungsten and mercury, indicating gold resources may exist. Alluvial sample results suggest recent claims in the northwest corner of the study area may also have gold resources. Portions of the study area are within the Randsburg Known Geothermal Resource Area while other segments are considered prospectively valuable for oil and gas and for sodium.

Jan 1, 1985

By Richard L. Fowler

An automatic steering control system was designed, installed and tested on a coal mine shuttle car. The system utilizes sensors and associated signal processing electronics developed under a previous phase of this contract. The automatic steering system performs the routine guidance functions of turning corners and straight-through tramming. The shuttle car driver retains full authority of speed, braking, load and unload functions and at any time may exercise his option with manual override or steering. Steering information is generated from signals derived from the existing Lateral Guidance sensor subsystem, and all operational features of the previously developed open-loop system are retained. Above ground system tests were conducted in a simulated mine constructed of wood panel ribs. Results were in good agreement with prior hybrid computer simulations undertaken to validate the basic control system over a broad range of conditions and to select system parameter values. The automatic steering system was successfully demonstrated in the above ground simulated mine to USBM technical representatives. Designed to meet USBM permissibility requirements, the system is ready for a Phase II underground testing program. Testing in actual underground mine environment is expected to provide additional data regarding recommended performance improvements and implementation techniques.

Jan 1, 1975

By C. H. Titus

This study consists of four descriptive Sections covering respectively: a state-of-the-art literature survey on ungrounded and grounded power systems, a report on literature pertaining to human threshold limits of electric shock, an analysis of the performance requirements of isolated systems and a section on design and performance specifications for an isolated system the final section includes copies, and translations where applicable, of the most important articles on foreign mining practice as well as some technical publications which could be difficult to obtain elsewhere. Section 2 - Literature Survey In analyzing the available literature on ungrounded systems it became apparent that too strict an interpretation of Section 1.1 of the Contract would limit the survey in both period of time analyzed and in available literature which discussed several types of power systems. Therefore, the survey was expanded to cover approximately the past twenty-year period and to cover literature which addressed itself to both ungrounded and grounded power system operation. Section 2 gives a brief summary of this literature survey and lists the important papers and books which were examined.

Jan 1, 1972

By D. D. Bush

Based on the results of this study, the underhand cut and fill stoping method, with mass destressing, is an effective method for controlling rock bursts and falls of ground for deep mining in the Coeur d'Alene Mining District. The procedure can be utilized to pull highly stressed pillars by converting from conventional overhand stoping methods or used as a primary recovery system. During the demonstration, only one minor rock burst occurred, with no injuries. The system facilitates accurate placement of vertical boreholes for effective mass destressing. Each mining cut is filled with cemented sandfill overlying a timbered mat that forms the back for the succeeding cut. For this demonstration, a cemented fill was mixed on the surface and piped to the stone. Costs for pillar recovery by this method are comparable and are considered cost effective over conventionally timbered overhand mining as a pillar recovery method.

Jan 1, 1982

By Robert F. Randolph

Introduction This paper is a descriptive analysis of injuries and fatalities at small surface bituminous coalmining companies in Pennsylvania. The purpose of analyzing a specific industry sector and location is to identify issues that might be missed in a wider analysis. Other studies of small mine safety (e.g., Peters and Fotta, 1994, Randolph and Boldt, 1997) have shown that the relationship between safety and mine size is not a simple one. Some injury types occur at higher rates at small mines, while others occur at lower rates. Consequently, an analysis limited to a specific type of mining can help identify hazards and issues specific to that sector. The results of this analysis will be useful for directing training, intervention, and research efforts towards the most prevalent causal factors and incident types. Procedures and Definitions Data sources The primary sources of data for this analysis were files provided by MSHA containing information collected under Title 30 Code of Federal Regulations, Part 50. These files, commonly referred to as “Part 50 data”, are provided though MSHA’s Program Evaluation and Information Resources directorate. Two primary types of injuries were selected from the Part 50data: Fatalities (MSHA “degree of injury” code 1) and lost-time injuries, otherwise known as nonfatal with days lost (MSHA “degree of injury” codes 2 through 5). Lost-time injuries involve either actual days away from work or days of restricted activity or both. Fatality and lost-time injury incidence rates were calculated using the standard MSHA formula: Number of injuries per 200,000 employee-hours. Additional information on company sizes and mine ownership was provided by the Pennsylvania State University College of Earth and Mineral Sciences. Time span A five-year time span was selected for this study. More than a single year of safety experience is usually needed to capture a broad range of incident types. Many types of injuries, especially fatal injuries, can be extremely rare, and may be missed if too short a time span is selected. However, a time span that extends too far back may begin to suffer historical threats to validity. That is, incidents that occurred several years ago may be caused by hazards that have since been remedied or may be related to mining practices and conditions that no longer exist. A five-year span offers a practical compromise between these two concerns. Consequently, the MSHA Part 50 data files from 1993 through 1997 were used. The 1997 file was in “preliminary” form at the time of the study, so small variations from the final 1997 “close out” file can be expected. Based on past experience, we do not expect the close-out variations to have a significant impact on the findings.

New Copper Deposit in Chile. - The recent copper discovery in Chile, made jointly by U.S.-owned Empresa Minera Utah de Chile, Inc., and Getty Mining Chile), Inc., awaits the passage of Chilean legislation which is expected to govern the terms of new foreign investment in the country's mining sector. Named La Escondida, the discovery is reported to have the potential for producing 100,000 tons of refined copper per year. This compares with Chile's total refined primary copper production in 1980 of 811,000 metric tons, and to U.S. refined primary production in 1980 of 1,122,000 metric tons derived from domestic material, and 89,000 metric tons from foreign material. U.S. Firms Buy Chilean Properties. - A bid of $18.1 million, made jointly by Chevron and St. Joe Minerals Corp., won over competing bids for the purchase of the Libra and Mena gold-silver-copper deposits in northern Chile. Chevron is the lead partner and owns 70% of the venture. The two properties purchased have not been developed to any significant extent. They are located near St. Joe's El Indio gold-silver-copper mine. The venture is also looking at the possible purchase of two other mines in the area.

Jan 1, 1981