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By Alan Quiroga

Nestled between Meridian Park and Howard University in the heart of Washington, D.C., the historic block between 14th, V and W streets North- west featured several original struc- tures, many of them dating to the 1800s. During its rich history, this square block has been home to a variety of different organizations including automobile showrooms and repair businesses, a parking garage, various industrial warehouses, and, in recent years, the headquarters of the renowned D.C. nonprofit Martha's Table. The revitalization of the buildings in this block also known as the Collection 14 project involved the transformation of aging and historical structures into a new multi-use development. The redevelopment project was distinguished by the retention of period street-facing building facades (to the extent possible) to preserve the character and culture of the historic neighborhood while revitalizing the block with some modern construction elements. The complexity of the project and difficult subsurface conditions required specialized and extensive sheeting, shoring and underpinning work to be performed. This project had many parties involved, including: • • • • Owner: Madison Investments Owner's representative: Compass Design & Development General contractor: McCullough Construction Civil engineer: Vika Capitol Structural engineer: Ehlert Bryan Architect: Perkins Eastman DC Geotechnical engineer: GEI Consultants Sheeting and shoring contractor: Steele Foundation

Aug 1, 2023

By D Wyatt, J Domenico, W Kow

Over the past few years developments in heavy minerals processing have concentrated on the mineral separation portion of the business. The best example of this would include new developments in rare-earth magnetic separators and associated flowsheet modifications. Except for some minor modifications in spirals, the æwetÆ side of the separation business has lagged behind the ædryÆ side. Basic concentrator design has not changed in 20 years. Recent pilot trials by Outokumpu Technology have shown the benefits of a new gravity flowsheet that combines density separation and spiral concentration on a variety of heavy mineral deposits. This concept is already well utilised within the iron ore industry. The synergistic combination of these two technologies allows smaller, simpler, and controllable gravity concentrators to be built while providing equivalent or better grade and recoveries of valuable heavy mineral. This is contrasted to the all spiral flowsheet characterised by the diminishing returns of multiple stages of spirals and associated recirculating loads. Examples of the flowsheets and associated benefits will be presented from a variety of cases.

Jan 1, 2001

By L. G. Jones

An approximate method of calculation is developed in this paper which allows duplication of radial unsteady-state gas flow computer results where Darcy's law applies, such as those reported by Aronofsky and Jenkins and Bruce, Peaceman, Rachford, and Rice. Moreover, the new calculation method can be used to obtain results for radial unsteady-state gas flow obeying the quadratic flow law proposed by Duwez and Green. Means are discussed for predicting well behavior at single or superimposed flow rates in finite or infinite reservoirs, determining reservoir rock properties from well-test data, reproducing and interpreting back-pressure test data, and determining the radial extent and reserves of gas reservoirs from well-test data. Example calculations are presented for gas flow following both Darcy's law and the quadratic flow law. INTRODUCTION Since the publishing of U. S. Bureau of Mines Monograph 7,1 most gas-well testing methods have been based on the equation q = y (pl2 - pw2)a, where q = production rate, pl and pw, are formation pressure and sandface pressure, respectively, and y and a are constants to be obtained from test data. These methods, used for predicting both deliverability and "open-flow" capacity of gas wells, have been useful and accurate in many cases but unsatisfactory in others. Even at best, however, they do not supply information about the formation or lead to an understanding of nonsteady-state gas flow in porous media. Many theoretically based studies2-4 of gas flow obeying Darcy's law have been made.' Since the partial differential equations which result from combining Darcy's flow law with the continuity equation are nonlinear, most of the published research consists of either numerical solutions or analytical solutions for linear approximating equations. Such solutions have been of limited value in field work due to their unhandy form and their failure to correlate most field data. There is evidence5,6 which indicates that Darcy's law is inadequate to describe gas flow at some flow rates of practical interest. A quadratic flow law: which reduces to Darcy's law at low rates, is more successful in accounting for experimentally observed behavior. This flow law has been applied successfully to a few hypothetical reservoir cases in work which has recently been published.10 However, these numerical solutions of the equations involved have been successful only on a special analog computer. Routine applications to field cases would be awkward and have not been attempted. The present paper describes an approximate method for computing nonsteady-state gas flow solutions which has been completely successful in predicting the results for both Darcy flow and quadratic flow obtained by elaborate numerical methods. The new calculation method allows determination of the observable variables in gas-well testing at constant rates. It is similar to the scheme of using a succession of steady states suggested by Muskat7 in that it makes use of steady-state and material-balance equations. It also is similar to the work of Aronofsky and Jenkins2 in that the new method includes Aronofsky and Jenkins' stabilized flow equation as a special case. It improves upon both of these calculation schemes in that it accurately describes all portions of reservoir history and suggests means of determining reservoir rock properties from well-test data. This paper deals only with production from a reservoir, in which case the rate is defined as being negative. The reservoir studied here is a homogeneous, disk-shaped porous body of uniform thickness, with all boundaries sealed except the inner radial boundary of the well.

By J. Shen

Direct methanol fuel cells have been the subject of considerable research in the last decade. Performance levels realized in cells, stacks, and systems show that this technology is a promising power source for a wide range of portable applications. A direct methanol fuel cell (DMFC) operates directly on a methanol fuel stream typically supplied as a methanol/water vapour or as an aqueous methanol solution in liquid feed DMFCs. The fuel streams in DMFCs are usually recirculated in order to remove carbon dioxide and to re-use the diluent and any unreacted fuel in the depleted fuel stream exiting the DMFC. The concentration of methanol in the fuel circulation loop is an important operating parameter because it determines the electrical performance and efficiency of the direct methanol fuel cell system. The methanol concentration in the circulating fuel stream is usually measured continuously with a suitable sensor, and fresh methanol is admitted in accordance with the signal from the sensor. There are many factors to consider in developing a methanol sensor suitable for DMFCs. These factors include sensitivity, cost, size, simplicity, reliability, longevity, concentration range, and dynamic response. In particular, reliability and low cost should be addressed. Methanol concentration sensors measure methanol concentration by means of detecting the variations of physical/chemical properties of the solution. In this work, methanol concentration sensors based on electrochemistry, electric-capacitance measurement, infrared sensing, ultrasound sensing, and other techniques are reviewed to discuss their advantages and disadvantages.

Jan 1, 2005

By H. Lind

The consumption rate of Estonian oil shale increases due to the growing rate of exported oil-shale oil. Estonian oil shale active resources in working mines are predicted until the year of 2025 when the consumption rate stays at the level of 12 tons per year. If the consumption rate stays at that level, new mines should be opened after 20 years, if the rate increases new mines should be opened even earlier. The predicted active resources in Estonian oil shale deposits are calculated for 60 years, based on the parameters of the power station technicoeconomics. As a result, there is a need to open new mines. One of the potential areas for surface mine is the Tammiku-Kose prospect area (Rheinbaun Engineering, 1996).

Jan 1, 2006

By John E. Young

U.S. Steel Corp.'s Winifrede mine is operated by Lynch District in the mountainous region of eastern Kentucky. This region is characterized by narrow finger ridges and precipitous slopes, which present both an opportunity and challenge in the design and selection of coal-handling facilities for the movement of coal from the section belts to the railrod cars. Lynch District selected diesel-powered locomo¬tives and 100-ton articulated cars capable of negotiating sharp curves. The drop¬bottom mine cars are equipped with longitudinally hinged doors that are auto¬matically opened and closed. Lynch District selected a large-diameter steel-lined borehole for lowering the coal approximately 1000 ft from the seam level to the valley floor railroad load-out point. Taking advantage of gravity, the presized coal is "lowered" vertically approximately 720 ft to existing entries of a previously abandoned mine. The coal is then conveyed horizontally into storage. The coal¬handling facility from the mine-car dump to the railroad load-out point is fully automatic through use of tone control. TV cameras are installed along the facility to continuously monitor the strategic points. The diesel locomotives are either directly operated or remotely radio-controlled, depending on the functions Per¬formed. U.S. Steel Corp.'s Winifrede mine is operated by Lynch District in the mountainous region of eastern Kentucky. This region is characterized by narrow mountain ridges and precipitous slopes which present both an opportunity and challenge in the design and selection of coal-handling facilities for the movement of coal from the section belts to the railroad cars. The narrow finger ridges precluded use of under¬ground haulage and, thereby, presented the opportunity to use high-capacity equipment on the outside bench. The precipitous mountain slopes, steepest at the Wini¬frede seam horizon, presented a challenge to select a solution for lowering the coal approximately 1000 ft from the seam level to the valley floor railroad load-out point. It was evident from the start of planning that these two factors predominated; namely, rail haulage and coal lowering, and solutions to these would determine the final design of the Winifrede mine coal-handling facilities. The Winifrede mine derives its name from the Wini¬frede Seam which comprises the total reserve recov¬erable from this facility. The seam is 5 ft high with a good siltstone bottom and competent shale or sandstone roof. The seam is at an elevation of 2700 ft where the mountain ridges are long and narrow. This configuration of the reserve was ideal for conveyor belt installation to transport the coal from the working face to the outside bench. The preclusion of underground rail haul¬age permitted an opportunity to review the type of locomotive power and to select high-capacity equipment without the limitations associated with underground systems. Since the basic electrical design of the mine was al¬ternating current, with rectification to direct current for shuttle cars required only in the face areas, there was no point in bearing the burden of additional cost of dc trolley installation. And, since the haulage would re¬quire only a few tunnels to negotiate sharp points and to reach the back side of the reserves, diesel power was selected for the haulage locomotives. To provide stability on the almost continuously curv¬ing track and to provide the maximum width of haul¬age equipment, both locomotives and mine cars, stan¬dard railroad gage was chosen to offer the largest choice of equipment. The decision was made to select a standard 45-ton railroad diesel locomotive but to lower the cab height to reduce tunnel excavation requirements. The mine car was the next challenge. Past experience in Lynch operations indicated that drop-bottom cars would be a successful application with the free-flowing coal. The search was for a drop-bottom car within the dimensions of the locomotive to discharge the coal in the shortest time. Numerous types were considered and visits made to various sites to observe cars in operation.

Jan 1, 1972

By Hiren J. Shah

Across much of New York City, the geology of glacially deposited soils follows a common sequence. Outwash sands generally overlie varved silts and clays, which lie above a basal till deposit underlain by the bedrock. Pile foundations at projects with such typical stratigraphy generally develop their axial capacities by extending below the fine-grained deposits into the till or the bedrock. Contrastingly, at a project site on the Brooklyn waterfront, high capacity piles were efficiently and economically installed by driving them into the relatively shallow glacial drift and till deposits which lay above thick fine-grained compressible glacial lake deposits. An unusual aspect about the foundation design at the Brooklyn project site is that, relatively short and high capacity piles were driven into the shallow glacial drift and till deposits, overlying the thick fine-grained glacial lake deposits. In order for this unusual foundation scheme to be feasible and economical, the piles needed to achieve their driving criteria in the upper strata. Consolidation settlements in the lower stiff and over-consolidated glacial lake deposits below the pile tips had to be relatively small. The paper discusses the unusual stratigraphy in this area of Brooklyn in greater detail with geologic profiles and engineering characteristics of the glacial strata. It also discusses the design aspects of the pile foundations, settlement estimates, a pile drive test program during design, results of the static load test program during construction, and production pile installation results.

Jan 1, 2008

Discussion of the paper of GEORGE S. RICE and H. H. CLARK, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2563 to 2571. NORMAN V. BRETH,* Pittsburgh, Pa.-It was my privilege to visit in the last two months on behalf of the U. S. Bureau of Mines 10 mines where electric shot-firing systems controlled from outside the mine are installed. I will describe briefly what I saw in some of these mines, which are located in Utah, New. Mexico, Oklahoma, Alabama, and Kansas. At a mine in Utah, 230-volt alternating current is used to fire the shots, which is taken from a small transformer in the substation. The shot-iring circuit is independent of all other wires and is tested for grounds every day. There are no lightning arresters on the firing circuit. Porcelain insulators are used inside of the mine, and glass outside. The switches are situated as follows: One in the substation, one in, the shot-firer's cabin, two at each cross entry; where the shot-firing circuit crosses the trolley wire a switch is placed on either side of the entry in series with the shot-firing circuit. The miners are checked in and out of the mine. The coal is undercut and is shot down with permissible explosive, the shots being connected in multiple. There are 75 to 110 shots fired each day. A great many times there are no missed shots. If not more than two or three are missed they are left until next day. The fan is kept running at full speed when the shots are fired. The shot-firing switch is closed only once and the whole mine is shot at once. At another mine in Utah, power wires are used for shot-firing circuits; 500-volt, direct current is used to fire the shots. The only sizes of wire used outside of the power wires are Nos. 8 and 14 B. & S. gauge. The return is connected to the pipe lines and track. Porcelain insulators are. used inside of the mine.

Jan 4, 1915

By Shengqi Chen

The reduction smelting of nickel laterites produces slag, consisting principally of the chemical components MgO, "FeO", SiO2, and A12O3, and ferro-nickel alloy. Despite the fact that the phase equilibria for the ternary MgO-"FeO"-SiO2 up to 1500°C is well established limited experimental data are available in the MgO-"FeO"-SiO2-Al2O3 system, which is relevant to commercial operation of the process. A methodology has been developed for the experimental investigation of the liquidus temperatures for the multi-component system MgO-"FeO"-SiO2-Al2O3-Cr2O3 in equilibrium with metallic iron. Experiments have been carried out using high temperature equilibration, quenching, followed by electron probe X-ray microanalysis (EPMA). Liquidus temperatures have been determined in the silica primary phase field in the composition ranges directly relevant to the Cerro Matoso S.A. ferro-nickel smelting slag. Liquidus isotherms have been determined for temperatures between 1450 to 1600°C. The study enables the liquidus to be described for a range of MgO/FeO ratios. It was found that liquidus temperatures in the silica primary phase field decrease significantly with the addition of AI2O3. Keywords: Liquidus temperature, ferro-nickel, pyrometallurgy, smelting

Jan 1, 2004

By D. C. Valdemeri, Oppermann J. P. Z., R. G. Schaarschmidt, C. S. Mendonca

This case study was conducted in an aggregate company, located at Estância Velha town, RS, Brazil. The study was based on the results of vibration monitoring mainly in terms of PPV (peak particle velocity) and frequency. Changes in the blasting design were performed to adjust the limits determined by the Brazilian standard NBR 9653:2005. Understanding the seismic wave attenuation for the site, changes in the blasting design were tested to fit the limits, such as reduction of maximum charge per delay, initiation orientation and sequencing and finally the replacement of accessories like "shock tube" by electronic initiation system. The results are shown below.

Jan 1, 2015

By Hideki Shimada

A low cost methodology that allows the determination of in- situ stress using oriented core specimens has been investigated. The technique can be used to determine the stresses during the early stages of a project, even in undeveloped areas of a mine. The research aim was to compare the experimental results estimated by the AE and DRA methods to those estimated by conventional ANZI (Australia and New Zealand Inflatable) cell measurements. The studies have been focused on fill stress tensor determination from a single oriented cored rock. In all cases the rock core specimens recollected the in-situ stress reasonably well compared with the standard overcoring method.

Jan 1, 2001

By G. W. Imholz

A number of interesting wells were drilled in north central Texas during 1940. The Shell Oil Company's Smith well in scc. 143, block I, H. and T. C. survey, Stonewall County, was completed for an initial production of 581 bbl. per day from the Mississippian limestone, with a total depth of 6065 ft. The same company's Patterson well, sec. 393, block D. H. and T. C. survey, Stonewall County, tested the Ellenburger limestone and was abandoned as a dry hole with a total depth of 6760 feet. In Nolan County the Tex-Harvey Oil Co. drilled a well in sec. 43, near the Tipton well, which was completed as a small producer in the Strawn section. The Tex-Harvey well tested this producing horizon but was abandoned as a dry hole with a total depth of 5210 feet. The Montour-Haggart well, sec. 184, block 2, H. and T. C. survey, Fisher County, tested the Strawn and was abandoned with a total depth of 5664 feet. The Georgian Oil Company's Blach, sec. 309, T. R. and L.. Shackelford County, encountered the top of the Ellenburger limestone at 4725 ft. After being plugged back to 3915 It. from a total depth of 4825 ft., the well tested 10 bbl, of oil per day and 300 bbl. of water. The W. I. Sothern No. 2 Carlisle well in sec. 293 was deepened to the Cambrian. The top of the Ellenburger was encountered at 6540 fcet. A wildcat well in Fisher County, the E. A. Stephenson-Maberry, apparently opened a new pool when the well encountered sand from 3298 lo 3302 ft. and was completed for 50 bbl. per day in the Cook sand horizon. In Jones County, the King Oil Company's Olsen well, sec. 158, B. B. B. and C. survey, extended the Avoca-Olander pool. The well was completed for 263 bbl. in 8 1/2 hr. from the Palo Pinto limestone, from 3298 to 3302 ft. Ungren-Frazier extended the Akard pool with No. I Akard, in the D. 'T. Bruce survey. The well was completed for 83 bbl. per day from the Cook sand, encountered from 2109 to 2126 feet.

Jan 1, 1941

By G. W. Imholz

A number of interesting wells were drilled in north central Texas during 1940. The Shell Oil Company's Smith well in scc. 143, block I, H. and T. C. survey, Stonewall County, was completed for an initial production of 581 bbl. per day from the Mississippian limestone, with a total depth of 6065 ft. The same company's Patterson well, sec. 393, block D. H. and T. C. survey, Stonewall County, tested the Ellenburger limestone and was abandoned as a dry hole with a total depth of 6760 feet. In Nolan County the Tex-Harvey Oil Co. drilled a well in sec. 43, near the Tipton well, which was completed as a small producer in the Strawn section. The Tex-Harvey well tested this producing horizon but was abandoned as a dry hole with a total depth of 5210 feet. The Montour-Haggart well, sec. 184, block 2, H. and T. C. survey, Fisher County, tested the Strawn and was abandoned with a total depth of 5664 feet. The Georgian Oil Company's Blach, sec. 309, T. R. and L.. Shackelford County, encountered the top of the Ellenburger limestone at 4725 ft. After being plugged back to 3915 It. from a total depth of 4825 ft., the well tested 10 bbl, of oil per day and 300 bbl. of water. The W. I. Sothern No. 2 Carlisle well in sec. 293 was deepened to the Cambrian. The top of the Ellenburger was encountered at 6540 fcet. A wildcat well in Fisher County, the E. A. Stephenson-Maberry, apparently opened a new pool when the well encountered sand from 3298 lo 3302 ft. and was completed for 50 bbl. per day in the Cook sand horizon. In Jones County, the King Oil Company's Olsen well, sec. 158, B. B. B. and C. survey, extended the Avoca-Olander pool. The well was completed for 263 bbl. in 8 1/2 hr. from the Palo Pinto limestone, from 3298 to 3302 ft. Ungren-Frazier extended the Akard pool with No. I Akard, in the D. 'T. Bruce survey. The well was completed for 83 bbl. per day from the Cook sand, encountered from 2109 to 2126 feet.

Jan 1, 1941

By C. H. Li, J. Washburn, E. R. Parker

Yield stress in single crystals of zinc was shown to be dependent on prior annealing temperature and rate of cooling after annealing. Rate of strain hardening beyond the yield was not sensitive to annealing procedure. A tentative mechanism for the effect was discussed. COMPARATIVE mechanical tests of metal single crystals generally show a large scatter of results. Many factors may contribute to this variation. The present investigation was undertaken to evaluate the influence of two factors not ordinarily considered of major importance—annealing temperature and cooling rate after annealing. Since plastic properties of crystals are thought to depend on the presence of lattice imperfections, it follows that a variation in properties should result from differences in the distribution and density of these imperfections. Furthermore, in the light of current theories of interaction between edge dislocations and lattice vacancies,' it seems possible that annealing temperature and subsequent rate of cooling might play a part in this distribution. Analysis of the effect of these variables on plastic properties may lead to a better understanding of the annealed state. Single crystals of zinc which have been strained in simple shear undergo complete recovery of mechanical properties upon subsequent annealing. This behavior is useful because a single specimen can be used repeatedly, thus eliminating the uncontrollable variables introduced by the use of many crystals. The test section of the crystals used for these experiments was a cylinder 1/8 in. thick with a cross-sectional area of about 1/3 sq in. The specimens were acid-machined from spherical single crystals 1 in. in diameter in such a way that the slip plane (0001) was at right angles to the axis of the cylinder. In testing, a shear stress was applied along one of the slip directions, [2110] in the (0001) plane.' All crystals, unless otherwise noted, were grown in a helium atmosphere from molten 99.99 pct pure Horse Head Special Zinc. Fig. 1 is a family of curves obtained from one crystal. Each curve was obtained by deforming the crystal to 10 pct strain at a rate of 3 pct per min, following an anneal of 1 hr at 260°C. The strain direction was reversed every other time so that no progressive change in shape of the specimen took place during the series of tests. Since the stress-strain curve was reproducible within a fairly narrow range under the same conditions of annealing, it was then possible to determine the effect of changes in annealing conditions. A crystal was tested repeatedly as previously described but the annealing temperature and rate of cooling preceding each test were varied (Fig. 2). Two cooling rates were used, approximately 30°C per min and 3°C per min. Annealing was conducted at three temperatures, 200°, 300°, and 400°C. For a given annealing time and rate of cooling the room temperature flow stress was higher the higher the annealing temperature. The increase in flow stress was small as the annealing temperature was increased from 200° to 300°C but rose rapidly when the annealing temperature was raised from 300" to 400°C. Faster cooling from the high temperature produced an even greater strengthening of the crystal. The curves were obtained in the order indicated by the numbers. The stress level associated with a certain annealing treatment was, within the limits of scatter, always the same regardless of the

Jan 1, 1954

By Yingxin Zhou

Data from these field studies and previous case study data have been combined to define ultra-dose seam mining environments and relate them to observed failure conditions. A rating system for ultra-close multi- seam design has been developed and field studies have verified the applicability of the design criteria according to geologic structures, lithology and spatial data. This rating system has been combined with design and depth considerations to create a protocol for quantitatively predicting potential damage in ultra-dose seam mining conditions. A brief discussion of the characteristics of ultra-dose seam mining and its related failure mechanisms is also presented

Jan 1, 1990

By E. E. Thurlow

The Geology Div. of Northern Pacific Railway Co. has adapted to its exploration efforts field procedures for geochemical sampling and semi-quantitative analysis which have been developed through research by the U. S. Geological Survey. The sampling is done in conjunction with reconnaissance geologic mapping on aerial photographs or during field checking of maps which have been prepared largely by photo-geologic interpretation. Stream sediment or soil samples are taken and readily soluble combined heavy metals are extracted with ammonium citrate followed by colorimetric titration with dithizone at the sample site. The effectiveness of this approach has been demonstrated both in positive and negative results, thereby assisting in the elimination of large areas of land from further immediate attention and in providing targets for followup exploration. An occa sional sample is submitted for spectrographic analysis as a check on the possible presence of other elements of economic significance. Field laboratory procedures are also being implemented for determining molybdenum, mercury, and other metals which may be valuable in themselves or useful as pathfinder elements in outlining mineralized areas. A lead-zinc occurrence in Oregon and a copper deposit in Montana were readily detected and outlined by stream sediment and soil sampling and a heavy metal anomaly that lacks obvious interpretation has been found in northwestern Montana. Detailed mapping and additional sampling are followed by other exploration techniques if warranted. Northern Pacific's program of reconnaissance mineral evaluation of company-owned lands and adjoining areas was outlined in a paper presented at the American Mining Congress meeting in Las Vegas four years ago. That report included policies and procedures with respect to mineral development on Railway Co. lands and may be referred to for information on these matters.1 In a sense this paper is a progress report on the use of geochemical prospecting in Northern Pacific's continuing mineral evaluation program. At this time there are positive results but as yet there is no real success story in the form of a minable ore body. GEOCHEMICAL PROSPECTING PROCEDURES The decision to use geochemistry as a reconnaissance exploration tool must be followed by research into sampling and analytical methods and into the interpretation of results. Various analytical methods were tried and evaluated by the Geology Div., including hot and cold acid extraction with and without fusion of the sample, panning and magnetic separation followed by dithizone testing of the magnetite, and cold aqueous extraction of metallic ions followed by indicator tests. Samples were first sent to the laboratory for analysis; later field laboratories were established and now virtually all testing is done at the sample site. It was concluded that, where applicable, the quickest dependable methods for reconnaissance use are the dithizone field tests for readily extractable heavy metals. This involves the simultaneous treatment of a sample, usually of soil or stream sediment, with two immiscible liquids; one a cold aqueous extractant (ammonium citrate) and the other a solution of dithizone in toluene or xylene.2 Dithizone is a colorimetric indicator that reacts quantitatively with copper, lead, zinc, and several other metals to form colored complexes in organic solvents. Results may be expressed in ml of 0.001 pct dithizone that are required to reach the blue end point, or calibration of the test results can be carried out with standard solutions of zinc; conversion factors would then be expressed in ppm, zinc equivalent. Calibration of dithizone solution with zinc standards indicates that 1 ml of 0.001 pct dithizone is equivalent to approximately 0.25 ppm of zinc. An authoritative report on dithizone field tests authored by H. E. Hawkes in the June-July 1963 issue of Economic Geology* states "The appeal of these techniques has been the simplicity and speed of the determinations as compared with more tedious laboratory determinations of trace metals in weathered rocks, soils, or plant materials. This obvious appeal, however, has often been more than matched by misuse of the method in such a manner that the results are

Jan 1, 1964

By H. W. Reinhardt, J. W. Dally

A dynamic photoelastic analysis of stress waves interacting with a free surface is described. The free surface is that of a bench with a fixed bottom so common in quarry applications. The stress waves are generated by line charges of lead azide (Pb N,). Four models of identical geometry are investigated with the direction of detonation of the line charge varied between the four models. Dynamic photoelastic patterns are recorded and analyzed to indicate which method of detonating the line charge produced the largest magnitude of tension at the free surface. The mechanics of rock breakage by means of explosives has received considerable treatment by many investigators including Duvall, Obert, Broberg, Rinehart, and Langefors1-11 over the past two decades. Indeed in more recent years several texts12-15 have been written on the topic, treating a wide variety of subjects which are logically related to the modern technique of rock blasting. In rock blasting the chemical energy of a concentrated explosive contained in a relatively small diameter borehole is utilized to fragment the rock. The explosive is transformed into a gas with enormous pressures which exceed 10-5 bars18 This high pressure shatters the rock in the area adjacent to the borehole and produces dilatational and distortional stress waves which propagate radially away from the borehole. The state of stress associated with these outgoing waves produces a system of cracks which extend for a few feet from the borehole. The breakage produced in this manner is limited as the dynamic stress in the pulse attenuates markedly with distance. In the absence of a free surface, the stress wave propagates away from the source without further fracture. With a free face of rock near the drill hole, another mode of breakage occurs which is due to scabbing failure of the layer of rock adjacent to the free face. These scabbing failures are produced by the reflection of the incident waves and the conversion of compressive stresses into tensile stresses sufficiently large to fracture the rock. The detailed nature of the interaction of the stress waves with the free surface is complex and difficult to treat analytically. However, dynamic photoelasticity offers an experimental approach which gives a fullfield visual display of propagating stress waves and the reflection process. Applications of static photoelasticity to solution of problems related to mining technology have become relatively common (see, for instance, Refs. 17 and 18) with a plastic model loaded to produce a state of stress representative of that occurring in the workings of a mine. The application of dynamic photoelasticity is ex tremely limited. Tandanand and Hartman19 have used a multiple spark camera to study fracture in glass and plastic plates impacted by a chisel-shaped tool. This paper describes a dynamic photoelastic analysis of stress waves interacting with a free surface. The free surface is that of a bench with a fixed bottom so common in quarry applications. The stress waves are generated by line charges of lead azide (Pb-N6). Four models of identical geometry are investigated with the direction of detonation of the line charge varied between the four models. Dynamic photoelastic patterns are recorded and analyzed to indicate which method of detonating the line charge produced the largest magnitude of tension at the free surface. Experimental Procedure The model illustrated in [Fig. 1] was fabricated from a sheet of Columbia Resin CR-39 to represent a bench with a fixed bottom. Properties of the CR-39 pertaining to these dynamic experiments are listed in [Table 1]. Scribe lines on 1-in. centers are used to identify locations along the bench face. The bench height was 8 in., the burden was 3 in., and the overall dimensions of the sheet, 16 and 18 in., were large enough to eliminate reflections from nonessential boundaries during the period of observation of the dynamic event. To simulate a charge in a borehole, a groove 0.062 in. wide and 0.080 in. deep groove was cut into the sheet from one side. The lower end of the groove was 1 in. or 1/3 the burden distance below the bottom of the bench. The upper end of the groove was 3 in. or one times the burden distance below the upper level of the bench. The groove was packed with 60 mg of Pb No per in. of length, and ignited with a bridge wire detonator. Four different ignition procedures were used to examine the effects of detonation direction on the stress wave interaction with the free face of the bench. In Test 1 the line charge was ignited at the top and the line charge detonated downward. In Test 2 the line charge was ignited at the bottom and the charge burned upward. In Test 3 the charge was ignited in the center with the top half burning upward and the bottom half burning downward. Finally in Test 4 the line charge was ignited at both ends simultaneously. Sixteen high-speed photographs of the photoelastic fringe patterns representing the stress wave propagation were recorded for each of the tests. A Cranz-Schardin multiple spark gap camera 20,21 was operated at framing rates which were systematically varied from 110,000 to 250,000 frames per sec during each test.

Jan 1, 1972

This paper is written as a supplement to that of Edwards, Baker and Knight on "The Geology of the Wonthaggi Coalfield" 1, the West Area pit being in an early developmental stage at the time of their paper. The thin seams to the west of Dudley Basin 2 had beenknown for many years but it was not until 1935 that it became necessary to work them. The West Area Pit came into production as Dudley Area Pit approached exhaustion in 1937. From available information it was estimated that early work would be in a 36in. bottom seam. The present top seam was not included in the reserves, but it was to be extracted where it proved thick enough for economical working.THE SEAMSEdwards, Baker and :Knight (1944) had insufficient information to correlate positively the West Area seams with those in the Dudley Basin. Their opinion was, however, that they were a westerly extension of the Bottom Seam. Since then the driving of the present north-east heading towards No. 4 Bench McBride Tunnel has established that the West Area seams are those worked as Bottom Seam in the Dudley Basin. West Area Top Seam is a seam that occurred above the Bottom Seam in the Dudley Basin. Only sporadic attempts have been made to work it in Central Area, because 30in. was considered an economic minimum height until recent times. This seam should not be confused with Top Seam, Dudley Basin, which lies some 300ft. above the bottom seam measures and except in isolated areas over deeper workings has been eroded away in West Area.

Jan 1, 1953

By Elton A. Youngberg

J. H. HEARDING, Jr.*—Extremely hard ferruginous chert (taconite) was encountered in driving a drift at the Fraser underground mine near Chisholm, Minn., on the Mesabi Iron Range. In order to get better results in drilling in this ground, it was decided to try tungsten carbide bits. In the beginning, 1½ in. tungsten carbide bits and 1 1/8 in. round-lugged alloy steel drill rods with "jack-stud" inserts were used. Considerable difficulty was encountered because the jack-stud became loose in the drill rods. Because there was not enough alloy steel drill rod on hand, we began to insert jack-studs in the ordinary high carbon drill rods and found, to our surprise, that there was less trouble with jack-studs working loose in these rods than there had been with the alloy steel rods. As a result, use of the alloy steel rods has been discontinued entirely. Under the heading "Drilling Procedures" the statement is made that all holes are started with detachable bits or conventional steel to prevent undue strain on the tungsten carbide bit inserts when collaring a hole on uneven ground. This practice was followed in our work originally for the same reason. It was soon found, however, that the holes could be started with the tungsten carbide without injuring the inserts if the drill operator was careful and did not give the drill too much air until the bit had a chance to seat itself in the rock. J. C. FRANZ*—In a discussion of other technical papers with reference to percussion drills and the use of carbide tungsten bits, it was my impression that the authors reported one of the first difficulties experienced with the use of standard, conventional percussion drills, was insert bit failures due to crushing of the bit inserts when the bits became dull. During the past few years, some of the rock drill manufacturers, I am told, have adopted an air drill for use with the carbide bits that have a lighter blow and faster rotation than the regular machine. This machine has been tested and the carbide bit failures have been considerably reduced. L. W. DUPUY†—The difficulties Mr. Youngberg mentions that were had with rod and coupling breakage call to mind similar troubles experienced at the Picacho mine in California near Yuma.6 The commercial couplings then available were found to be tempered almost to brittleness. Rod breakage was usually in the threads near the end of the rod. The highly-tempered couplings would break as soon as the rod broke. The solution was to thoroughly anneal the couplings and to put in only a very mild temper. Subsequently the alloy used in making the couplings was changed from the original by the manufacturer, but still only a very mild temper was used. The result was that the softer coupling would give but would not snap and release its hold on the broken rod thread. Fishing jobs were reduced to the few where the rods broke at the rod end of the thread. Thread breakage on the rods was further reduced by thorough annealing prior to tempering. The data Mr. Youngberg presents regarding the use of carbide inserts on long blasthole drilling is most interesting and it would appear that the use in this manner of percussion drills and carbide bits will have many applications. W. M. WOODWARD*—How many feet of hole, on the average, do you get from a tungsten carbide bit, and is there much variation from this average? E. A. YOUNGBERG (author's reply) —In recent months the 2 in. tungsten carbide bit footages in long hole drilling hake varied from 115 .to 140 ft monthly. The footages obtained from individual bits vary from several feet to over 300 ft, however the life of a majority of the bits will be within 25 ft of the average.

Jan 1, 1950

By Walter Fuchs

IT is now generally conceded that coal is the product of deposition and transformation of debris of forests and swamps.29 Ample data are available to illustrate the metamorphosis of biochemical substances through biological action; other data show the progressive regional metamorphism existing in coal beds;25 and numerous examples of change effected by intrusion of igneous dikes into coal deposits have been established .R3 However, often the relative importance of the biological and the geological factor in determining the character of the various natural coals is a debatable question. Since both biological and geological factors are ever present in nature, the problem, at first glance, would appear to resemble certain probability problems: specifically the simultaneous toss of two coins, with the biological factor as heads and the geological as tails. The probability is 2:I for the combined effect of both factors, as compared to the exclusive effect of either one, if the a priori probability is the same for each factor. This condition can be analyzed by a thermodynamic treatment of data, which may be obtained from a consideration of pertinent biological, chemical, geophysical and geological facts. SYNOPSIS OF BIOLOGICAL AND CHEMICAL FACTS The biosphere is not sterile; i.e., microorganisms are always present. Microorganisms have been established in the ocean deep, under the ice of the polar regions, in the sand of the deserts, and in swamps far below the surface. The various biological media may be acid, neutral, or alkaline, and they may or may not be readily accessible to air. Microorganisms are encountered almost everywhere, except where the temperature is not within the range tolerable by microbial life. Of course, with changing conditions, the type of microorganisms will change. All chemical products of life-proteins, fats, carbohydrates, lignins, waxes, resinsmay serve as a habitat of microorganisms. In the decomposition of a medium, some microorganisms macerate organic matter mechanically and remove certain constituents for their own nutrition; others decompose a large part of the organic matter but may leave certain constituents undecomposed. Some attack only certain specific ingredients of the organic matter. All of them build up cell substance. The nitrogen content of the medium largely determines the degree of decomposition. Below 1.7 per cent nitrogen, growth of microorganisms and hence decomposition of organic material is retarded; consequently organic material will accumulate.17,32 Such accumulations of organic material may give coal eventually. Coals differ in type and rank. The nature of the original vegetation and the conditions attending the transformation of the accumulated debris determine the type of coal such as bright, splint, cannel, and algal or boghead coals. Chemical analysis of representative samples of a given type of

Jan 1, 1941