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By George A. Savanick

Coal mine roof shales fracture preferentially at slickensided surfaces because of weak or nonexistent adhesion between two slickensided rock surfaces. The purpose of this Bureau of Mines research was to characterize chemically the thin film of smooth, glossy material that makes up the slickenside. This material was analyzed by electron spectroscopy and ion scattering spectrometry while in place on the rock surface and by standard methods of quantitative chemical analysis on concentrate removed from the rock. These analyses showed that the chemistry and mineralogy of the slickensides are similar to that of the adjacent shale.

Jan 1, 1974

By Warren W. Krech

Rock property data is needed over a wide range of parameters for the optimum execution of rapid excavation research. Eight rock types were chosen by the Bureau of Mines for a standard rock suite for such research. Large rock blocks were quarried and the standard physical and mechanical properties measured and documented. The eight rock types that comprise the rock suite are Barre Granite, Berea Sandstone, Dresser basalt, Holston Limestone, Salem Lime-stone, Sioux Quartzite, St. Cloud Gray Granodiorite, and Westerly Granite. Geologic, petrographic, physical-property, and mechanical-property test data are reported for each rock type. The information is the first step in the building of a comprehensive property listing for the eight rock types. A limited number of rock cubes are available from the Bureau of Mines Twin Cities Mining Research Center for use by researchers to broaden the information available on the suite.

Jan 1, 1974

By R. F. Chaiken

The Bureau of Mines has carried out experimental and theoretical studies with prilled and pulverized ammonium nitrate-fuel oil (AN-FO) mixtures containing varying amounts of fuel oil in an attempt to quantify the effects of stoichiometric composition, nonideal detonation behavior, and expansion volume on the production of CO, NO, and N02 fumes. Experimental fume measurements were obtained in the Bureau's large closed gallery facility (7.2 X 104 liter expansion chamber) and in the standard Crawshaw-Jones apparatus (90--liter expansion shamber) using a prepackaged charge configuration containing about 450 g of explosive.4 The theoretical calculation of toxic fumes was achieved with an equilibrium detonation code called "TIGER,," Contrary to initial expectations, the NOx (= NO + N02) fumes from the large gallery test were found to be in essential agreement with the Crawshaw-Jones results. It was also concluded that (1) "TIGER" calculations offer a good approach to the prediction of toxic fumes; (2) there is a basic problem in extrapolating laboratory measurements of CO fumes to mine conditions--this being due to postdetonation oxidation of CO to CO2; and (3) the detonation velocity decay rate of an explosive is a useful experimental parameter for correlating toxic fumes production with nonideal detonation behavior.

Jan 1, 1974

By P. B. Lorenz

Wettability measurements and laboratory waterflood tests were compared under a wide variety of conditions. Experiments were conducted with synthetic and natural crude oils, treated and untreated outcrop and oilfield sandstone cores, and synthetic brines with and without caustic, detergent, or phosphate additives. Measurements were made on equilibrated and unequilibrated systems at 77° and 150° F. Wettability was evaluated by the Bureau of Mines method from capillary pressure curves determined with a centrifuge. The waterflood data were fitted by empirical curves; the parameters of the curves characterize primary and subordinate production and also give the ultimate oil recovery. Results showed that wettability measurements at 77° F were useful predictors of recovery efficiency in waterflood tests run at both temperatures. Oil recovery in the early stages of waterflooding increased with increasing water wettability; however, the ultimate recovery was highest at a slightly oil-wet condition. The oil displaced at highest speed in the centrifuge was correlated with ultimate recovery in waterflood tests. Chemical additives to the brine sometimes lowered wettability and also sometimes improved waterflood recovery, but wettability and recovery were not correlated with additives present. The effect of additives on recovery in waterflooding was best seen in water-oil ratio curves.

Jan 1, 1974

By J. S. Miller

This report presents a complete coverage of results from Bureau of Mines preliminary research and the field application of explosive fracturing techniques to prepare oil shale for in situ recovery of shale oil. Small-scale surface tests were conducted to determine the feasibility of using a nitroglycerin-base explosive for creating rock fractures. Prior to underground testing, surface and near-surface tests with liquid explosives showed that explosions in sheetlike layers simulating underground fractures would propagate effectively. Successful surface experiments were conducted using layers of explosive placed between glass plates and explosive-saturated sand confined in small-diameter metal tubes. The tests in glass-plate reservoirs and metal tubes demonstrated that nitroglycerin would detonate and the explosion would propagate in cracks as thin as 1/32 inch and through distances up to 12 feet. In a shallow field test, nitroglycerin was detonated in a vertical crack in limestone and produced extensive fracturing. Explosive fracturing tests were performed in oil shale formations on seven sites near Rock Springs, Wyo. The procedures included (1) displacing and detonating nitroglycerin in natural or hydraulically induced fracture systems; (2) detonating nitroglycerin in wellbore shots; (3) displacing and detonating nitroglycerin in induced fractures followed by wellbore shots using pelletized TNT; and (4) detonating wellbore charges using pelletized TNT. The research on oil shale formations demonstrated that nitroglycerin displaced in a natural or hydraulically induced fracture would detonate, and the explosion would propagate through the explosive-filled fracture. Shooting a pattern of wells in oil shale at 100-foot depth with wellbore charges of pelletized TNT developed a satisfactory interwell fragmented zone. Tests performed on other sites at depths to 385 feet caused fragmentation of rock around the wellbore and provided interwell communication. Fourteen methods used to evaluate the extent and degree of fragmentation in the explosive fractured oil shale are discussed.

Jan 1, 1974

By Parviz F. Rad

The Bureau of Mines used a linear cutting apparatus equipped with a 7-inch disk cutter to cut grooves in marble, limestone, granite, and quartzite under a normal force of 7,000 lb. The size distribution of the muck for various grooves was determined through sieve analysis. A statistical search showed that Weibull distribution describes the size distribution better than other available functions. Results indicate that fineness modulus, chip population, and dimension of the largest chip can be used as indicators of cutting efficiency. The results correlate with those obtained from the boring machines and other lab experiments. Application of the principles established through this work to the operation of boring machines is explained

Jan 1, 1974

By Fred N. Kissell

Methane concentration peaks were measured by the Bureau of Mines at coal mine working faces during entry development. The statistical distribution of peaks was found to be normal or log normal depending on how well the methane was being mixed into the ventilation airstream. A normal distribution indicated good mixing, whereas a log-normal distribution indicated that mixing was poor. In addition, the "highest" peaks over selected intervals were found to fit a type I extreme-value distribution, a result similar to that obtained while mining longwall faces.

Jan 1, 1974

By Raymond M. Stateham

Infrared and displacement studies were made of an unsupported roof in Kaiser Steel Corp.'s York Canyon coal mine, Raton, N. Mex. Monitoring of the roof continued until the roof over the area was caved. Loose slabs in the roof, about 6 inches thick, were detected by means of associated thermal anomalies, using remote-sensing infrared instruments. Displacement measurements taken during the study indicate that roof movement was cyclic in nature; the cycles appear to have been related to the mine work cycle (work days to idle days).

Jan 1, 1974

By Albert W. Deurbrouck

The performance characteristics of five hydrocyclone coal washers were evaluated to determine the sharpness and efficiency of separation that might be anticipated in commercial operation. The hydrocyclone overflows contained generally good clean coal products that would require little re-treating to remove misplaced high-gravity material. The underflows, however, contained from 63.6 to 36.7 percent of misplaced low-gravity material, which would require secondary cleaning to provide acceptable clean coal yields.

Jan 1, 1974

By R. H. Sprute

This report describes Bureau of Mines laboratory test results in electrokinetic dewatering and consolidation of metal-mine tailings. Tailings were placed in 0.3-cubic-foot Plexiglass models, and dc potential was applied until dewatering ceased. Time-oriented measurements of water removal, changes in resistivity, and power consumption were recorded during the dewatering process. Dewatered material was tested for moisture content and density. Equipment and procedures were developed to optimize the method for unclassified mill tailings from a particular mine in the Coeur d'Alene, Idaho, district. Results indicate the method to be highly effective in dewatering and consolidating this material.

Jan 1, 1974

By Verne E. Hooker

This Bureau of Mines report summarizes the results of modifications in the borehole deformation gage design and subsequent changes in the overcoring techniques. Modifications in the borehole deformation gage have greatly improved the creep characteristics and enhanced the versatility of the gage. In situ field tests in competent rock near St. Cloud, Minn., provided sufficient data to compare the reliability between gages and new techniques in obtaining good engineering estimates of stresses. Near-surface horizontal stresses at the test sites are compressive and biaxial in nature.

Jan 1, 1974

By R. H. Sprute

This report describes Bureau of Mines laboratory test results in electro-kinetic dewatering and consolidation of metal-mine mill tailings from five mines in the Coeur d'Alene, Idaho, district. Classified (coarse) tailings, slimes, and unclassified material were separately tested. Tailings were placed in 0.3 ft3 plexiglass models, and dc potential was applied until dewatering ceased. Time-oriented measurements of water removal, changes in resistivity, and power consumption were recorded during the dewatering process. Moisture content and density of the dewatered material at test end indicated the method to be generally effective for all materials examined, but best results were achieved with well-mixed unclassified tailings.

Jan 1, 1974

By John E. Kelley

A method for measuring the spark-shower radiance of metals when abraded on a grinding wheel was developed by the Bureau of Mines for evaluating the sparking tendency of metals. The radiance was measured in units of emissive power per solid angle per area of the detector. Over 100 metals were tested and rated relative to commercially pure iron. The metals tested included elemental metals, iron binary and ternary alloys, iron-carbon ternary alloys, commercial steels, nonferrous alloys, and a few hard-metal compounds. Some alloys were synthesized; others were obtained commercially. Alloys that possessed good strength properties were emphasized for selection. The results indicate that the spark-shower radiance of plain carbon steels and carbon alloy steels was greater than that of pure iron. Certain elements, particularly vanadium and chromium, reduced the sparking tendency of iron. Stainless steels and particularly nickel alloys displayed low spark-shower radiance. Some metallic elements had much lower radiance than iron; others, much greater. Plain carbon steels, heat treated to a variety of hardnesses, gave radiance values that generally increased with increasing hardness. The effect on sparking tendency of an increase in hardness of an alloy steel was studied. The sparking tendency increased with an increase in hardness to a maximum, then decreased with a further increase in hardness.

Jan 1, 1974

By James R. McVey

A new method for measuring deformations of rock surfaces in underground excavations has been suggested by Dr. James Powell of Brookhaven National Laboratories (BNL) and subsequently developed and successfully demonstrated in a mining environment by the Federal Bureau of Mines, Spokane Mining Research Center (SMRC) and Brookhaven National Laboratories. The system uses 35-mm photography of targets strategically located on surfaces of interest, such as across the roof and on the sides of a mine drift or tunnel. The optimum tar-get, as determined in this investigation, consists of a white ?X? made with 1/8-inch-wide reflective tape on a black 6-inch square. Photographs, taken in pairs from two separated camera positions and at regular time intervals, were analyzed at the Bureau by hand and at Brookhaven National Laboratories using techniques and equipment similar to those used in cloud chamber film analysis. Test results show that deformation-measurement accuracies of better than ±0.020 inch in a drift that is 20 feet wide can be expected. This degree of accuracy, plus providing displacement data in the X, Y, and Z directions (rather than the one direction formerly possible), makes this a noteworthy and useful tool for industry as well as for mining research.

Jan 1, 1974

By Russell E. Griffin

Dielectric constants and dissipation factors were measured by the Bureau of Mines for 13 simulated lunar rocks over the 20-to 100-megahertz frequency range by means of the susceptance-variation method. Measurements were made at room temperature and normal atmospheric pressure. Results are presented and some comparison is made with data reported by others. The rocks used include a broad range of physical characteristics and chemical compositions from the large areas of volcanism in Oregon and northern California, and two nonvolcanic types. These rocks make up a suite of rock standards used by a group of laboratories engaged in lunar research. The data presented will add to the basic scientific and engineering knowledge needed to utilize extra-terrestrial mineral resources for support of future space missions.

Jan 1, 1974

The Bureau of Mines found sulfur hexafluoride (SF6), released from a lecture bottle, to be an ideal gaseous tracer for studying mine ventilation systems. Air samples were collected in glass syringes and analyzed by electron-capture gas chromatography. In these studies, the lower limit of detection was about I part per billion by volume (ppb) of SF6 per part of air. Experiments conducted in a Pennsylvania limestone mine showed this technique useful in evaluating the effectiveness of auxiliary fans, measuring low flow velocities, probing the air circulating near a working face region where ventilation appeared to be poor, and estimating volumetric flow rates in airways of large cross-sectional area and having low flow velocities. This technique was also used in a western vein-type metal mine to measure the amount of return air being recirculated into the intake air due to leakage through old stoped areas.

Jan 1, 1974

By D. J. MacDonald

Wettability measurements and laboratory waterflood tests were compared under a wide variety of conditions. Experiments were conducted with synthetic and natural crude oils, treated and untreated outcrop and oilfield sandstone cores, and synthetic brines with and without caustic, detergent, or phosphate additives. Measurements were made on equilibrated and unequilibrated systems at 77° and 150° F. Wettability was evaluated by the Bureau of Mines method from capillary pressure curves determined with a centrifuge. The waterflood data were fitted by empirical curves; the parameters of the curves characterize primary and subordinate production and also give the ultimate oil recovery. Results showed that wettability measurements at 77° F were useful predictors of recovery efficiency in waterflood tests run at both temperatures. Oil recovery in the early stages of waterflooding increased with increasing water wettability; however, the ultimate recovery was highest at a slightly oil-wet condition. The oil displaced at highest speed in the centrifuge was correlated with ultimate recovery in waterflood tests. Chemical additives to the brine sometimes lowered wettability and also sometimes improved waterflood recovery, but wettability and recovery were not correlated with additives present. The effect of additives on recovery in waterflooding was best seen in water-oil ratio curves.

Jan 1, 1974

By Jack L. Henry

A laboratory and a pilot-plant-scale investigation has been conducted by the Bureau of Mines to examine possible sources of nitride defects in the production of magnesium-reduced titanium sponge. The production of alpha-stabilized nitride inclusions in hot-rolled titanium plate from air contamination of sponge during its manufacture has been experimentally demonstrated. Magnesium-reduced sponge prepared from air-contaminated magnesium or when contaminated by an air leak during reduction, vacuum distillation, or inert gas sweep, shows very large variations in nitrogen content. Refractory nitrides, delta TiN and epsilon Ti2N have been identified in this sponge. The highest incidence of inclusions resulted from sponge that was reduced by air-contaminated magnesium and from sponge subjected to air contamination during the vacuum distillation cycle and during helium sweep. Air contamination of sponge during the reduction cycle was not nearly as effective in producing inclusions. Tests showed that color and texture may not be reliable criteria for locating defects during sponge inspection. Maintenance of good vacuum-tight integrity, filtration of molten magnesium prior to charging into the reduction retort, and mechanical attrition of sponge to pulverize and disperse nitrides are suggested as practices to lower inclusion incidence in commercial titanium ingots.

Jan 1, 1974

By Russell R. McLellan

As part of an effort to develop new or improved placer mining technology in the Tertiary gold-bearing channel gravel of northern California, the Bureau of Mines conducted investigations at the old Badger Hill placer mine in Nevada County, Calif., to collect data and information regarding drilling and sampling methods and deposit characteristics. Sampling studies involved the collection and processing of 400 tons of large-and small-volume samples from drill holes, underground workings, surface pits, and blasthole rounds. A total of 355 samples averaging 2,296 pounds per sample provided reasonably accurate data for analysis of the gold distribution. These studies indicated that the bulk of the gold is within 40 feet of bedrock in stacked, lenticular zones of cemented gravel that are largely confined to the relatively narrow, meandering course of the deepest portion of the bedrock channel. Drilling studies involved the testing of truck-mounted rotary, buckett and vibratory drills, none of which proved to be a completely versatile tool for sampling quickly and reliably both consolidated and unconsolidated gravel..

Jan 1, 1974

By Mark I. Copeland

This study was conducted by the Bureau of Mines to determine the effect of steel reheating practices in burning natural gas on the amount of silicon required to prevent the formation of copper on steels containing up to 1 wt-pct Cu. Formation of copper, which causes surface hot shortness, was readily prevented by as little as 0.3 wt-pct Si and by 2 vol-pct excess oxygen in the furnace atmosphere when reheating steels containing up to 0.8 wt-pct Cu. Up to 0.8 wt-pct Si content and careful control of reheating conditions were necessary for steels containing 1 wt-pct Cu. Best conditions for these steels were reheating to 2,200° F (1,205° C) in burning gases containing 2 vol-pct excess oxygen, and then to higher temperatures in gases of 6 vol-pct excess oxygen. Slag and mold wash were not detrimental on steels reheated for 8 hr by a soaking-pit-type furnace schedule, but they were problematical on steels heated for 2 hr by a pusher-type furnace schedule. The effect of silicon contents on scaling rates also was determined.

Jan 1, 1974