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Improve the reliability and accuracy of subsurface images using constrained tomography with enhanced ray-tracing capabilities. Background Geophysical tomography is a technique for imaging the structure of a rock mass using seismic or radio waves, in the same way that medical CAT scans image human tissue using X-rays. Tomography has found numerous practical applications related to mining, including lithologic and structural characterization, fracture detection and fluid monitoring, void detection, and evaluation of stress state and integrity of mine structures. Problems Two fundamental problems have largely prevented geophysical tomography from enjoying the tremendous success achieved by medical tomography. The first is a consequence of practical limitations on the placement of sources and receivers of wave energy: ideal resolution can be attained only when the region being imaged is entirely surrounded by sources and receivers, so that it is crossed by rays traveling in all possible directions. When such coverage is impossible or impractical, the inversion becomes underdetermined: there id not enough information in the measured data to provide a mathematically unique solution. The second major problem in geophysical tomography is the necessity for detailed ray tracing. Commercial software, as well as previous U.S. Bureau of Mines (USBM) software, employs a ray-shooting algorithm that may be unable to model some ray paths when velocity contrasts are larger than about 100%. These ?shadow zones" result in loss of data and degradation of reconstructed images.

Jan 1, 1994

By A. Wahab Khair

"This paper deals with the description of the capabilities of a unique rotary coal cutting simulator which has been designed and fabricated at West Virginia University. It operates under the simulated mining conditions with in-situ stresses (horizontal and vertical stresses) being applied to a coal block of 18 in. x 15 in . x 6 in located in a suitably designed confining chamber. Cutting drum rotation can be varied from 1 to 40 rpm with the capability of stopping the drum after a predetermined number of rotations. Tests can be performed with four different bit angles, 15, 30, 45 and 60 degrees . A maximum of seven bits could be used in seven different orbits. Various cutting depths up to a maximum of 4 in. is possible.Monitoring devices constitute, Linear Variable Differential Transformers (LVDTs), pressure transducers, cascade Impactors, flow meters, flow controls and drum cutting speed. LVDTs are used to monitor the displacement of the coal block as well as the depth of cut. Pressure transducers are used to monitor the changes in pressure, both due to the thrust and due, to the intermittent cutting nature of the rotary cutting. Flow controls will be used to run the drum at a set rpm between 1 and 40 and to provide a different rate of advance. All the above mentioned devices can be operated and monitored by a fully automated control system. Six-stage cascade impactors are used to determine the mass distribution of dust along the rotation path of the drum. The fracture size, shape and Intensity can be studied by optical microscopy and the dust entrainment by using high speed photography.This equipment will basically be used to study the fracture mechanism in coal, associated with operating and in-situ parameters and further relate It to dust generation and entrainment In underground coal mines."

Jan 1, 1988

By O. M. Bishop

The Douglas fluorite property is in the Empire district of eastern Pope County, Ill., which lies near the west boundary of the productive Southern Illinois fluorspar field in Hardin and Pope Countios. Production from mines on the Douglas property accounts for about one-half of the 72,000 tons of fluorspar with which the Empire district is credited. This output was from the Sycamore, Pierce, Slapout, and Empire veins, which are normal fissure veins of little displacement along which there has been local wall-rock replacement by fluorite.

Jan 1, 1949

By Robert L. Marovelli

The thermal conductivities of six rocks were measured by the transient line source method over the temperature range of -850 to 1,500° F. Close-fitting ceramic probes were used in 0.065-inch-diameter holes drilled through 5-to 6-inch-thick rock specimens. Taconite, granite, quartzite, and basalt were used in the tests. The method yields absolute data and is applicable to both laboratory and in situ measurements.

Jan 1, 1965

By R. E. Stiles

The modified perchloric--EDTA method devised by the Bureau of Mines for the determination of copper in high-grade samples gives results that are more precise and more accurate than those from the classical sulfuric-iodometric method. Although the perchloric--EDTA method is more costly than the conventional method, the savings in time alone largely offsets this difference. Specifically, the modifications wade in the more conventional procedure comprise (1) use of perchloric acid instead of sulfuric acid for dissolution of copper minerals, (2) precipitation of copper as copper sulfide from dilute perchloric acid solution, (3) wet oxidation and dissolution of the precipitated copper sulfide, (4) use of larger amounts of indicator than those employed in the Schwarzenbach method of titrating low-tenor copper solutions with disodium ethylenedinitri10-tetraacetate and murexide indicator, and (5) use of refrigeration to partially stabilize aqueous solutions of the indicator.

Jan 1, 1966

By J. A. Organiscak

Enclosed cabs are a primary means of reducing the silica dust exposure of equipment operators at surface mines. The National Institute for Occupational Safety and Health (NIOSH) has investigated various factor effects on enclosed cab air filtration system performance. Factors experimen­tally investigated were intake filter efficiency, intake air leakage, intake filter loading (filter flow resistance), recirculation filter use and wind velocity effects on cab penetra­tion (inside to outside cab concentration ratio). Adding an intake pressurizer fan to the filtration system was also investigated. Results indicate that the intake filter efficiency and recirculation filter were the two most influential factors on cab penetration .Use of a recirculation filter significantly reduced cab penetration over the intake air filter by itself due to the multiplicable filtration of the cab interior air. Cab penetration was also affected to a lesser extent by intake filter loading and air leakage. Adding an intake pressurizer fan notably increased intake airflow and cab pressure while providing only minor changes to cab penetration.

Jan 1, 2008

By Ryan G. Wade, Mark K. Larson

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are studying the time-dependent response of rock stressed along weakness planes. The objective is to improve mine safety by reducing the number of roof falls that cause injuries and fatalities to miners. Researchers conducted direct-shear tests on mudstone overcored from a coal mine roof. Results showed frictional strength weakens with displacement along the shearing planes. Results of direct-shear creep tests also showed time-dependent deformation. Test measurements were compared to classical analytical models. Results suggest that risk of roof collapse may be decreased through layout and support design to reduce creep rates and thus slow progression toward failure.

This report summarizes the work performed by the Bureau of Mines on the development of analytical procedures for determining metallic and interstitial impurities in high-purity tungsten. Fourteen published methods and seven unpublished methods are briefly described. Carbon, hydrogen, nitrogen, and oxygen, in microgram to higher quantity levels, can be determined by several methods. Trace levels of 29 metallic impurity elements can be determined by optical spectrography, X-ray spectrography, and other instrumental methods.

Jan 1, 1968

By Alvin M. Cummings

"INTRODUCTION During July and August 1943, the Bureau of Mines undertook an investigation of the Trego lead-zinc mine, near the town of Platteville in Grart County, Wis. as part of a general investigation of the zinc-producing area of southwestern Wisconsin. The work was done when every effort was being made to increase the production of metals important to the nation's war program.The Bureau of Mines completed eight churn-drill holes and sampled mineralized faces in the mine workings to determine if further exploitation was justified in an area between the mine and a zone previously drilled to the east.Following the investigation described herein, intermittent operations were resumed. Except where otherwise stated, this report describes conditions only to the time of completion of the Bureau of Mines investigations.ACKNOWLEDGMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. The Mining Division, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual investigative work and prepares the final report. The Metallurgical Division, O. C. Ralston, chief, analyzes samples and performs beneficiation tests.The investigation described in this report was conducted under the immediate supervision of the author and 0. W. Terry, mining engineer of the Bureau of Mines, with the assistance and advice of E. D. Gardner, re¬gional engineer, and E. P. Barrett, district engineer. Final data were prepared under the direction of Paul Zinner, acting chief, Minneapolis Branch, Mining Division.A. V. Heyl, Jr., and A. F. Agnew of the Federal Geological Survey cooperated with the Bureau's engineers and made lithologic studies required during the drilling program.The cooperation of W. N. Smith and O. E. DeWitt of the Vinegar Hill Zinc Co. and Francis Piquette of the Piquette Mining Co. facilitated the investigation to a great extent."

Mar 1, 1948

By G. W. Jones

[One of the mJor c~ctivities of the Bureau ~f l;ine;: is the j.a-onotion of sdetp in mining a.nJ other inclus tries. 13 cor'ncc tlcn td t~l tiiene activities the 3~.sccu r:e termine? t'le cwl.os:lon ha~arls 95 n,o;r.?xs tibla Tases, vzpor s, aid scli3s aqi iavestig~ ter rnrI.?ns of controlling s-~fi. prevpri ting eqlosians.]

Jan 1, 1941

By G. W. Jones

[One of the mJor c~ctivities of the Bureau ~f l;ine;: is the j.a-onotion of sdetp in mining a.nJ other inclus tries. 13 cor'ncc tlcn td t~l tiiene activities the 3~.sccu r:e termine? t'le cwl.os:lon ha~arls 95 n,o;r.?xs tibla Tases, vzpor s, aid scli3s aqi iavestig~ ter rnrI.?ns of controlling s-~fi. prevpri ting eqlosians.]

Jan 1, 1941

By E. R. Bauer

The U.S. Bureau of Mines is investigating strata interactions associated with mining of multiple coal beds to provide the mining industry with improved methods of planning and developing multiple coalbeds, conserving resources, and increasing the safety of underground coal mining. This study involves analytical predictions and underground observations of longwall development ground control problems at a south-central Pennsylvania coal mine affected by subsidence induced by multiple-seam mining. As predicted, strata interactions were found in upper mine areas mined over lower mine gob. Observations revealed roof deterioration accompanied by excessive water inflows in the first 170 ft after crossing the gob line as mining entered and exited the subsided area (over the lower mine gob). In contrast, superimposed mine areas and areas mined a substantial distance out over the gob showed no signs of interaction with previous lower seam mining, again as predicted.

Jan 1, 2010

By Oliver Bowles

"The American Consul at Guatemala City reports that the Guatemala Marble Mining Company is preparing to operate a marble quarry about 13 miles from the railroad station of Zacapa, which station is a little over 100 miles from Puerto Barrios, the nearest port from which the product may be shipped. The deposit is extensive, and though somewhat broken up in places, great quantities of sound marble are available. It is claimed that the marble is equal in quality to the best product of the Italian Carrara quarries.Access to the quarry by rail is obtained by a spur track of the International Railways of Central America (Ferrocarril Internacional de Centro America) from Marmol, 3 miles south of Zacapa. This spur is about 5 miles long and terminates at the foot of the mountains. A double-track incline cable-way 2000 feet in length has been constructed to bring the marble down the mountain. From the top of the incline to the quarry there is a railway six miles in length over which the rock will be hauled by two side-geared Shay locomotives."

Mar 1, 1920

By Kenneth M. Earl

In its program of investigation of deposits of strategic minerals, the Bureau of Mines did some development drilling at the Tapley deposit in an endeavor to find an additional source of copper. There are accounts that many years ago the property had some production; there are several old, inaccessible shafts apparently sunk on a vein in rhyolite or diabase. The waste dumps of these shafts contain considerable sulfides, chiefly pyrite and chalcopyrite. To cut the vein below the old mine workings, the Bureau of Mines? diamond-drilled five holes aggregating 1,204 feet. No significant copper mineralization was found.

Jan 1, 1950

By Arthur S. Swanson

The DuBois fluorite property in the southwestern part of Hardin County, Ill., has been active intermittently since 1904 and has produced an estimated total of 1,000 to 2,000 tons. The persistence of the vein and the stratigraphy suggested extensions of the ore body formerly mined. The Bureau of Mines investigated the property by core drilling early in 1944. Four holes were bored which totaled 1,106 feet and extended along a strike length of 1,150 feet. The data obtained in the course of the investigation are presented in this report.

Jan 1, 1948

By G. R. Palmer

The Bureau of mines evaluated the elution of uranyl carbonate from a strong base resin with a mixed carbonate eluant in a fluidized system. The system consisted of a multiple-compartment ion-exchange (MCIX) elution column with a continuous flow of solution, except for short periods when the resin increments were withdrawn. The exchange of uranyl carbonate from the mill-loaded strong base resin with an eluant composed of 1.0 [M] NaaCOs plus 1.0 [M] NH4HCO3 was studied. The effects of solution flow rate, aqueous-to-resin flow ratio, column diameter, compartment height, initial resin concentration, and column length were examined. The experimental data indicate that for the eluant examined, a resin residence time of 240 minutes is necessary to attain 90-percent elution efficiency. Also provided is a technique for sizing an elution MCIX column form pilot plant experimental data.

Jan 1, 1979

By Raymond M. Stateham

Microseismic noise rates and slope movements were measured in an unstable area along the north wall of the Tripp-Veteran pit, Kennecott Copper Corp., Ruth, Nev. Low-noise, wide-band microseismic geophones were located at various points in the wall, and the change in distance across open fractures, resulting from instability, was determined by repeated measurements between fixed points set on each side of the fractures. The microseismic noise rate increased and decreased with corresponding increases and decreases in the rate at which the fractures opened. The microseismic noise rates and changes in width of the fractures show excellent agreement, and the two types of measurements complement each other in monitoring the progress of pit wall failure.

Jan 1, 1971

By Lowell B. Moon

Regardless of how a mineral deposit in first discovered or by whom, any mining enterprise based upon it must pass through a preliminary stage of exploration. The common understanding of ?exploration? among mining engineers is well-expressed by Jackson and Knaebel:3/ Exploration work ranges from that performed by the individual prospector employing only the simplest tool, and equipment to elaborate campaigns involving the expenditure of largo stuns of money end the use of churn- car diamond-drilling equipment, large test-pitting crews, or sometimes a regular mining organization. In any event, the object is to determine as accurately as possible, with the funds available, the size, shape, and other characteristics of the ore bodies and their average value or grade.

Jan 1, 1945

By Harold C. Pierce

"INTRODUCTION During the years 1941 to 1945, the United States produced less than one-half of one percent of all primary nickel, whereas the nation's consumption of the metal amounted to nearly three-fourths of the world's supply. Although postwar nickel consumption probably will be less than wartime consumption, trade- estimates for the next 10 years are well above the average established during the 1930-1940 decade. The greatest consumption is expected in nickel alloys, particularly nickel-alloy steels. 3/ The greater use of nickel cast irons and nickel-clad metals also signifies an expanding nickel market. In anticipation of the postwar demand for nickel, and realizing the seriousness of the ""have not"" position of the United States with respect to this metal, the Bureau of Mines, sent an engineer 4/ into the lower Copper River region of Alaska during the summer of 1944 to investigate the nickel deposits near the head of Canyon Creek. Samples from the Spirit Mountain nickel prospect were sufficiently encouraging to justify more intensive exploration. As a result, a program of surface trenching, systematic sampling, and detailed mapping of the property was adopted and directed by a Bureau of Mines engineer 5/ in the summer of 1945."

Aug 1, 1946

By D. K. Dysinger

In this U.S. Bureau of Mines study, neodymium metal of 99.8 pct purity was prepared by electrolysis of Nd203 salts dissolved in a molten fluoride electrolyte. The metal was electrowon in a molten state at current efficiencies of 50 to 60 pct. Oxygen and carbon were the major impurities detected in the product. During operation of the small-scale laboratory cell, a number of technical problems including anode effect, low oxide solubility in the electrolyte, high neodymium metal solubility, reactivity of the metal with the cell materials, and back reaction of the metal with the anode gases were encountered. Approaches to improve cell operation and prospects for commercial adoption of the electrolytic production of neodymium metal are discussed.

Jan 1, 2010