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Introduction The Coal Mine Roof Rating (CMRR) is a roof classification system. It was first introduced to the mining community in 1994.The CMRR filled a longstanding need to quantify geologic description of coal measure rocks into an engineering value that could be used for mine design. It has now been written to a user-friendly visual basic code that can be run on any PC with a Windows operating system. Background Rocks that form the roof of coal mines can vary widely and quickly in composition, extent, and defects. This results in an equally broad range of rock properties that can substantially affect the ability of the rock mass to form a stable mine roof. The CMRR was designed to evaluate the properties of the coal mine roof rock mass that contribute to its weakness and convert them into a relative strength rating from 0 to 100. These properties include the cohesion and frequency of discontinuities like bedding, slips, shears, and joints; uniaxial compressive strength (UCS); and moisture sensitivity. With simple lab and field tests and observation, the CMRR can be calculated by technical and operating personnel with a minimum of training. The CMRR has been widely accepted in both U.S. and international coalfields. As a result, a number of roof control applications have been found for the CMRR. It is currently used as an input component in the Analysis of Longwall Pillar Stability(ALPS) program, which is used to design longwall chain pillars. Incan be used as a criterion for determining the appropriate width of mine entries. It has also been used to indicate the appropriate length of cut in weak ground. The CMRR can be used as a strength parameter to characterize inter burden between mined seams in the numerical modeling of subsidence effects. In any area where an estimation of coal measure rock mass strength is required, the CMRR can be adapted to fill this need. How It Works Originally designed to be used with underground exposures, the CMRR can also be calculated from core. The chisel test for bedding cohesion and the ballpeen hammer test for UCS are inappropriate for core. These tests have been replaced by point load testing both axially and diametrally. Two other measures that are common to standard core logging—Rock Quality Designation (RQD) and fracture spacing—are also used to estimate rock weakness. With these easily obtained parameters, the CMRR can be calculated from core and used in the mine planning and exploration phase. The input screens allow calculation of the CMRR for both underground exposure and core. The CMRR is reported both as a “dry" value and as a groundwater-adjusted value for moisture-sensitive rocks. There is a graphical output report featuring a lithologic column with annotated unit ratings and a roof bolt symbol representing the height of the bolted horizon. Another important feature is an AutoCAD interface. This feature allows the export of located CMRR data directly to an AutoCAD layer in XYZ form. In this way, drill hole data can be inserted directly to a base map.

Apr 1, 2003

By W. M. Weigel

"Sand is one of the most useful and, fortunately, one of the most common mineral commodities. By far the largest proportion of the production is used in construction, including all forms of building, concrete and paving, sand for this purpose is produced in every State in appreciable amounts. Excluding send used for railroad ballast, molding sand stands not in tonnage produced, followed by glass sand.Special sands. In addition to the above, many grades of sands, with special characteristics, are used in industrial processes, and may be classed in a group as ""special sends"". This includes filter sand, sand blast sand, engine sand, abrasive send, fire or furnace send, special flooring sand, roofing sand used as a finish for prepared roofings and pottery placing sand sand blast and filter sand have been discussed in previous reports.Very few send companies depend upon the production of any one of these grades, as their source of revenue. They are generally especially prepared from the bank run of sand by different methods of screening or washing, or may, in some instances, be by-products from the production of ether grades. Many companies not now producing them might be able to supply local demands by a slight addition to their plant. In nearly all cases, they command a better price than the usual grades of building sand.Definitions and Properties.Engine sand, or traction sand, as it is sometimes called, is used to prevent the slipping of the driving wheels of locomotives, or other self-propelled vehicles, on wet or slippery rails. Its greatest use is, of course, for railroad locomotives, but street cars use considerable amounts and mine locomotives require its use. As the send must be very dry when used, most consumers have their can drying equipment, so it is often shipped damp, with its natural water content on what resulting from washing by the producer."

Oct 1, 1924

Flexible hoses with rated working pressures up to 40,000 psi are used when high-pressure water jets are employed to cut rock or improve the performance of mining machines. Hose failures at such high pressures can result in serious injuries to workers. The Bureau of Mines used fatigue and burst tests to investigate the failure modes of high-pressure hoses at their rated working and burst pressures. Fatigue failure, at rated working pressures, occurred when the inner liner of the high-pressure hose broke, allowing water to seep through the wire wrapping, although the reinforcement wires did not break. At the burst pressure, all hoses failed catastrophically when the reinforcement wires broke. Low-pressure hoses placed over the high- pressure hoses for safety failed to contain water released by catastrophic failure.

Jan 1, 1987

By W. T. Millar

Magnetite mines in the Sterling tract, Orange County, N. Y., were operated almost continuously from pre-Revolutionary days until 1923. The Red-Back mine, one of several in this tract, was discovered in 1780; operated briefly in 1880; and abandoned, presumably because the iron ore contained considerable sulfur. The mine is in rough, mountainous country, with altitudes ranging from 500 to 1,100 feet. The magnetite deposit occurs in complex metamorphosed pre-Cambrian formation and is thought to be a replacement of limestone by magnetite. A dip-needle survey, completed in 1916, traced magnetic anomalies for a mile along the outcrop. A preliminary examination of the Red-Back mine was made by W. T. Millar, Bureau of Mines engineer, in December 1942. The Bureau of Mines bored seven diamond-drill holes aggregating 2,727.6 feet during the winter of 1943-44. A zone of magnetite mineralization was intersected in each of the holes.

Jan 1, 1949

By Walter T. Ackley

[The geophone has occupied a prominent position as a mine signalling device since its first introduction. The Bureau has carried out tests at different times with a view to improving the early geophones. The following paper describes briefly the adaption of the vacuum-tube audio frequency Amplifier to a new form of geophone. It is not intended to convey the idea that the results described are sufficient to warrant the drawing of definite conclusions as to the practicability of the electrical geophone, but the data and tests liven herein are made public because of their possible use to the industry and as a result of inquiries received as to the feasibility of such adaptions and modifications of the early geophones. Because of the limited time available to the authors, only one geophone with its auxiliary amplifier was constructed. As is well known, two geophones are necessary in order to determine the direction of a sound. Although the principles upon which the electrical geophone operates appear to be fundamentally correct, it is not possible to state whether two such devices 'rill function as efficiently, (as regards determining direction of sound) as the present geophone. In order to operate efficiently as a direction finder, the amplifiers of the electrical geophone must each amplify with exactly the same degree of magnitude. By proper design and adjustment this can probably be accomplished without greatly complicating the design. inasmuch as audio frequency amplification is used, no tuning; is necessary as is the case with tuned radio-frequency circuits. The same filament and plate batteries can be used to operate the amplifiers and by the use of dry cell tubes, requiring shall filament and plate currents, it if believed that a compact, portable and practical instrument can be evolved. Further investigations of the electrical geophone should be conducted to determine the points outlined in this preliminary report.]

Jan 1, 1924

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

4. Preliminary Study - Remote Seal Checker 4.1 Introduction Determination of the completeness of each individual seal at the time of its emplacement is essential for an effective remote sealing system. A satisfactory seal checking technique should provide a signal which: (1) indicates percentage completion as the seal is emplaced (2) provides a definite indication of a complete seal (3) indicates the size of the unsealed area if a complete seal is not feasible This information is required to establish the need for additional seal material, the need for additional seals, and the risk likely involved in entering the mine., In many situations it is as important to know the quality of a seal as it is to build an effective one. It is likely that with repeated use the remote sealing technique developed by Foster-Miller Associates will be sufficiently reliable and predictable to preclude the seal checking requirement. It is recommended, however, that each seal be checked during construction to insure its completeness and increase the level of confidence so necessary in reopening the mine. 4.2 Description of General Problem Several characteristics of remote mine seals are important in considering techniques for evaluating the effectiveness of these seals. These include:

Jan 1, 1973

Increase the recycling of critical and strategic materials by simplifying the indentification and segregation of scrap. Background Because the United States is dl-most totally dependent on imports of such critical metals as chromium, cobalt and nickel, Bureau of Mines research has been directed towards conserving these metals by increasing the recycling of the complex scrap materials that contain them. Experienced scrap sorters, using the traditional techniques of object recognition, spark tests, chemical spot tests, color, apparent density, and magnetic properties, can adequately sort a wide variety of alloy groups. However, the complex nature of new materials entering the scrap market has made sorting both more difficult and more important. Some new alloys contain so many components that separation by discrete alloys becomes a prerequisite for effective recycling. The Bureau has completed Investigations on two methods for rapidly sorting complex scrap mixtures. One method uses a combination of two low-cost instruments. The other uses a single sorting instrument. Both approaches are reported.

Jan 1, 1986

By an Slo, J. J. Forbes

"INTRODUCTION This is the first of a series of information circulars dealing with the control of roof and the prevention of accidents from falls of rock and coal. These circulars are being published to focus attention of the coal-mining industry on this most prevalent source of fatalities and injuries and to present factual information that should be helpful in reducing loss from these causes.Records of fatal accidents in the coal mines of the United States, from all causes, have been kept since 1906; during this period approximately 30,000 men have been killed by falls of rock and coal in the bituminous-coal mines, and more than 7,000 men have lost their lives in the Pennsylvania anthracite mines from the same causes. From 1906 to 1930, about 900 men were killed annually by falls of rock and coal in bituminous-coal mines, and about 200 men were killed annually in anthracite mines during the same 25-year period. From 1931 to the present time, the number killed annually from falls of rock and coal has averaged more than 500 men in bituminous-coal mines and about 125 men in Pennsylvania anthracite mines.Numerically the record of accidents from falls of rock and coal shows improvement, but on a percentage basis and on a million-man-hours-of-exposure basis little, if any, improvement has been made during the past 40 years. The cold fact is that, year after year, about 50 percent of all those killed in coal mines in the United States lose their lives from falls of rock and coal."

Apr 1, 1948

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

SUMMARY The objective of this program was to develop a system to extinguish coal mine fires by remote sealing of the underground passageways. The system developed had to be versatile enough to function under a wide range of operating conditions, including large variations in passageway geometry, depth of mine, water conditions, both in the mine and at the surface, and rubble in the mine passage. The system developed had to include instrumentation for the remote probing of the passageway prior to sealing, a system for sealing the mine passages, and instrumentation for remote monitoring of the quality of the seal during and after construction. These objectives were successfully achieved during this program. The remote mine sealing capability of the system was satisfactc rely demonstrated in a field test conducted at the Eastern Associated Coal Corporation Federal No. 1 Mine in Grant Town, West Virginia. The remote sealing consists of: (1) A sonar initial probing system which can operate satisfactorily even in the presence of dense smoke. The system is capable of determining both the local passageway geometry, identifying the presence of cribs and other obstructions, and the position of the borehole in the mine passage. (2) A mine sealing material system which utilizes fly ash for making the complete seal or as a bulk filler in conjunction with a urethane, froth foam, seal topping system. The choice of using fly ash alone or fly ash with foam topping depends on a number of factors, such as quality of seal desired, time available per seal, depth of borehole, passageway geometry, and water holding require¬ment. The fly ash-foam seal is a better seal, capable of sealing against a higher water head than fly ash alone. The fly ash sealing

Jan 1, 1973

By Fred N. Kissell

In this report the importance of diffusion in controlling the emission of methane in mines is examined. An in-situ diffusion parameter is defined and calculated for a hypothetical unfractured lump of coal in the Pittsburgh and Pocahontas No. 3 coalbeds. The values obtained are similar to those obtained with lump coal in laboratory experiments.

Jan 1, 1972

Prevent collisions between large mine-haulage trucks and smaller vehicles parked in areas not visible to the haulage-truck operator, Approach Two electronic systems were developed to detect the presence of vehicles in the blind areas of a parked haulage truck. The systems can warn haulage truck operators of presence of vehicles that are blocked from view. The systems do not apply for trucks in travel. How It Works The systems use electronic transmitting techniques-one system is based on low-frequency radio waves and the other on very-high-frequency radio waves. Each system requires that a signal transmitter be mounted on the smaller vehicle to be detected. Continuous signals from this transmitter are sensed by receiving antennas mounted on the right front and rear of the large haulage truck. Upon receiving a signal, the receiver energizes warning lights and a buzzer in the cab of the haulage truck, alerting the operator to a possible collision hazard. Detection distance is adjustable, depending upon the size of the haulage truck, but a minimum of 30 feet was the design goal.

Jan 1, 1990

To restore ventilation and prevent the accumulation of explosive or toxic gases by quickly installing substitutes for stoppings blown down by an explosion. Approach Temporarily replace blown down stoppings with a parachute-shaped brattice which can be erected in minutes. How It Works The self-sealing brattice is secured to the roof, ribs and floor by anchoring its nylon edge strip at several points using extensible poles, shads, or available projections such as roof bolts. The air pressure in the entry pops open the chute of lightweight sailcloth, forcing it tightly against floor, roof and rib. See Figure 1. This emergency brattice has been tested at two locations in the Bureau's Experimental Mine at Bruceton, Pennsylvania. In a test last December, one MESA inspector wearing full rescue apparel (including self contained breathing apparatus) installed a self sealing brattice in an entry at the Bruceton Mine. Although he did not have any previous experience with the device, he easily erected it in slightly less than 10 minutes, using two extensible supports (pogo sticks). Research to improve and refine the self-sealing brattice is continuing.

Jan 1, 1977

By R. Hogg

"Some basic features of the science and technology of particle systems are reviewed in the context of agglomeration processes. Emphasis is placed on the force of interaction among particles and with their environment and on their dependence on particle characteristics and interfacial phenomena. The complex role these forces play in the various stages of agglomerate formation, growth, consolidation and structure development, and their influence on final product properties is discussed.INTRODUCTION Agglomeration is an example of a process where the technology has generally preceded the science. Process development• has very often been by trial-and-error albeit with an eye on some basic principles. Nevertheless there is' a scientific basis to the process and a better understanding of the fundamentals can surely lead to improvements in process design and control.Successful processes for the agglomeration of fine particles depend on proper control of the adhesional forces between particles, to encourage agglomerate formation and growth and to provide adequate mechanical strength in the product. At the same time the rheology of the particulate system can be critical to the rearrangement of particles necessary to permit densification of the agglomerate and the development of an agglomerate structure appropriate to the end-use requirements.AGGLOMERATION SYSTEMSUltimately, the performance, of any agglomeration process depends on the• characteristics of the particles and their environment. The specific effects, however, are often complex and may be very difficult to pinpoint by simple observation of the process. A typical agglomeration process involves a number of concurrent or consecutive steps - adhesion, growth, compaction, etc., - each of which is affected by the characteristics of the system, but not necessarily in the same way. The effect of particle size, say on agglomerate growth may be quite different from its effect on compaction and its optimum value may differ widely from one stage to the other. Obviously there.is a general need for compromise in the design and operation, of agglomeration systems. Furtnermore, an understanding of the details of the process and their complexities can be critical to process optimization and improved product quality control."

Jan 1, 1989

By D. E. Wolfson

The Bureau of Mines carbonized 21 coal samples from Fayette, Greene, and Washington Counties, Pa., at 900° C, using the Bureau of Mines-American Gas Association (BM-AGA) method, and determined yields of products and physical properties of the coke. These samples represented high-volatile A Pittsburgh, Sewickley, Waynesburg, and Upper Freeport and medium-volatile Upper Freeport and Lower Kittanning coals. About 20 percent of all coals presently carbonized in commercial coke ovens in the United States are mined in Greene and Washington Counties, principally from the Pittsburgh seam. Sulfur content of the Pittsburgh coals in these counties is moderately high (1.0 to 3.2 percent) but, because of extremely large reserves, accessibility to eastern United States markets and excellent blending characteristics to yield strong coke, these counties will continue to be an important source of metallurgical coals in the future. Most coals from the other seams contained more than 2 percent sulfur, which would limit their use as metallurgical coals.

Jan 1, 1968

By F. M. Carlson

Comparisons are made between the results of the Buckley-Leverett and Kern solutions, which describe immiscible displacement of oil by gas in a linear system and the results obtained from a less restrictive numerical model. This model takes into account the effect of compressibility of the oil and gas and the effect of allowing changes in the amount of gas in solution in the oil. These effects are best exemplified by imposing large pressure drops across the system. With these large pressure drops, comparison of the model solution with the Buckley-Leverett solution reveals that the Buckley-Leverett solution provides estimates of recoveries at breakthrough of the gas that are too low. In contrast to the model, the Kern solution predicts breakthrough recoveries that are too high. A modification to the Kern solution is presented to facilitate more accurate predictions of recovery at gas breakthrough for gas injection at pressures higher than the saturation pressure of the oil.

Jan 1, 1974

By Parviz F. Rad

The Bureau of Mines conducted groove cutting experiments in marble, lime-stone, granite, and quartzite with a 7-inch disk cutter under a normal thrust of 7,000 lb. The values of muck weight per unit length, specific energy, cutting coefficient, and groove depth for each of these rocks were determined for groove spacings ranging from 0.1 to 4 inches, and from these results the values of optimum and critical spacing were computed" The results indicate that compressive strength may be used to predict some of the cutting characteristics of the independent grooves. Considering all the cutting characteristics, particularly those for the interacting grooves, Shore hardness, coefficient of rock strength, and torsional velocity correlate with cutting characteristics better than do other physical properties. Some of the field applications of the principles established in this report are identified.

Jan 1, 1974

Provide reasonably priced, reliable fire protection for AN-FO haulers. Approach An automatic fire sensing and suppression system for AN-FO haulers was developed and on-vehicle tested. How It Works The system works in two ways to protect personnel from dangerous and unpredictable AN-FO fires. First the system senses and suppresses fires on the truck before they spread to the AN-FO in the bunker. This design was chosen because AN-FO truck fires generally start when combustible liquids (such as diesel fuel, hydraulic fluid or lubricating oils) are ignited by hot surfaces mainly on three areas: the engine, the transmission or the power take-off. These fires are quickly sensed by a linear temperature sensor strung throughout these three areas. The system then warns the operator and automatically suppresses the fire by discharging 30 pounds of multipurpose dry chemical extinguishing agent through a network of fixed hoses and nozzles. Second, this system includes six spot thermal sensors mounted inside the bunker on the truck to monitor the AN-FO temperature in case a fire does spread to the bunker area. If the bunker temperature rises to 190° F, a loud siren is sounded to warn nearby per-

Jan 1, 1981

Improve the safety of mine workers by developing a means of forecasting impending roof falls in underground mines. Approach The Bureau of Mines, through in-house and contract research, has developed the Roof Fall Warning Device. This battery-operated, portable electronic system forecasts roof falls by detecting and interpreting high-frequency rock noise, The technology has shown potential for detecting stress-related failures in a variety of underground environments. How It Works All geologic materials produce high-frequency acoustic emissions when they encounter an increase in stress. These ultrasonic frequency range events ( >20kHz) are well above the audible range of human hearing, very small in amplitude and duration, and can only be detected with sophisticated electronic equipment.

Jan 1, 1990

Reduce costs of surface mine reclamation by improving scaper operating efficiency and reducing tire costs. Approach The Wheel Slip Monitor senses and compares the peripheral speed of a scraper's four tires 10 the true ground speed of the scraper, and alerts the operator if any of the tires exceeds a predetermined amount of slip. This system helps scraper operators reduce wheel slip during the loading cycle, thereby improving the loading efficiency of the scaper and reducing tire wear and damage. How It Works The system consists of five ultrasonic doppler velocity-sensing devices for measuring the speed of each wheel as well as the true ground velocity (see photograph). Each sensor produces an electrical output signal having a frequency proportional to the speed of the tire or terrain. The signals are conveyed through electrical cables to a control box in the operator's cab where they are converted to voltages proportional to individual wheel speeds (see photograph). The signals are further processed to activate a blinking red light, corresponding to any individual wheel which is slipping, and to sound a beeping tone that is audible to the scraper operator. The rate at which the light blinks and the tone beeps is proportional to the degree of slip. Alerted, the operator can take corrective action.

Jan 1, 1985

By Wilbur I. Duvall

The borehole deformation gage and overcoring techniques developed by the Bureau of Mines form one of the primary methods of determining in situ rock stress. This report describes a least squares method of calculating the average rock stress components in the horizontal plane from more than three diametral deformation measurements in a vertical borehole. This least squares analysis provides a means of determining the multiple correlation coefficient, the variance, and the scatter for a set of deformation measurements. From this information, confidence limits can be calculated for the secondary horizontal principal stresses and their directions. The material presented in this report can be used as a guide to the development of least squares solutions for stress measurement techniques other than the borehole deformation method. Since the statistical information that results from the least squares method is extremely useful in the interpretation of results, it is recommended that a least squares analysis be used on stress measurement data whenever possible.

Jan 1, 1979