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By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By Donald J. Knight

HEAT Treatment at 1500' F of a mild steel containing 0.1 pct C, in an atmosphere which is oxidizing to both carbon and iron, results in the progressive oxidation of the metal surface with little or no change in the carbon content of the underlying metal. Further heat treatment of the scaled metal in either a neutral atmosphere or in a vacuum may or may not result in the decarburization of the metal depending upon the physical nature of the scale. It is apparent that if a continuous layer of oxide is present on the steel surface, the reaction OScale + Cmetal Cogas cannot progress since the SO formed gas would be unable to leave the oxide/metal interface. Thus, in order for the reaction to progress, the oxide must be cracked or porous. Vacuum heat treatment at 1500" F of samples with a thick continuous oxide scale showed no decarburization of the steel. However, when cracks were introduced mechanically into the scale prior to the vacuum heat treatment notable decarburization of the metal resulted and a structure as shown by Fig. 1 obtained, i.e., reduction of the crack walls to ferrite. With reference to the diagram of Fig. 2, it would appear that a mechanism of the following type takes place. Carbon atoms arriving at an oxide/metal/void interface, such as 'A', Fig. 2(a), can combine with oxygen atoms from the scale and leave the reaction site as Cogas thereby reducing the oxide to metal. On a greatly magnified scale, Fig. 2(b),this will appear as a ferrite projection along the crack wall. Carbon atoms entering this projection can react with oxygen atoms at point 'C', which is a new interface, and so on leading to a progressive growth of the ferrite along the crack wall and to the surface, Figs. 2 (c) and 1. It would appear that the only means by which thickening of the ferrite film can take place is by a diffusion of oxygen through the ferrite film to react with carbon at the newly formed ferrite/ void interface. Since the diffusion rate of carbon is reportedly much greater than that of oxygen, and since there is a low probability factor of oxygen and carbon atoms arriving simultaneously at the same site on the ferritehoid interface, there will be a tendency for more rapid lengthening than thickening of the ferrite layer, as is observed.

Jan 1, 1962

By Fidelis T. Suorineni

The Ashanti mine, located in Obusai, Ghana, West Africa, has been in production for over 100 years, and is currently the second largest single gold producer in Africa. The mine covers a concession area of 434 square kilometers with four main ore types: the quartz vein type, disseminated sulphide type, supergene sulphides and transition ore, and granitoids stock works (visible gold and quartz veinlets). Various mining strategies and methods have been employed for the mining of the narrow-vein ore at Ashanti. In recent years, the mine owner: Ashanti Goldfields Company Ltd. has embarked on a mine-wide expansion program to boost production to a target of one million ounces per annum. With the rapid depletion of its high-grade ore, a suitable mining method was required to produce a high tonnage at low cost to meet production objectives. This paper discusses how the Ashanti mine applied Canada experiences in mining technology to boost production, and the impact that the differing geological settings between the two countries had on the stope performance at the Ashanti operations. Experience developed at the Ashanti mine led to innovative modifications for stope layout and design methods in relatively poor ground conditions.

Oct 1, 2001

By S. Mishra, C. Shon, D. Saylak

Only 40% of fly ash generated by the power plants in US are recycled and used for commercial applications. Of these, the high lime, Class C ash had been preferred. Systematic laboratory and field-scale studies have shown that, by including calcium chloride in the mix design of stabilization of roadbed materials, both Class C and Class F fly ashes can be effectively utilized. Test data reveal that the addition of calcium chloride to the system accelerates its curing rate, thereby increasing early strength and long term durability of the constructed road. For road construction, a preblended Class F fly ash–CaCl2 system tends to be more forgiving than the Class C fly ash–CaCl2 system. The former system produces more durable roads. The role of calcium chloride as an accelerator in these systems is discussed along with a mathematical model developed for fly ash- CaCl2 stabilized roadbed systems.

Jan 1, 2007

By Wilfried Ufer

[1. Einführung in die Problematik 1.1 Die Bedeutung des Schildausbaus Seit fast 30 Jahren ist die Konkurrenzsituation auf dem Primärenergiemarkt der Bundesrepublik Deutschland durch einen von Erdöl and Erdgas geführten and insbesondere gegen die Steinkohle gerichteten Verdrängungswettbewerb gekennzeichnet, der den Steinkohlenbergbau zu tiefgreifenden RationalisierungsmaBnahmen zwang. In diesem Zusammenhang kam es Anfang der 70er Jahre zur Einrührung des Schildausbaus, der eine erhebliche Produktivitätssteigerung in den Strebbetrieben zur Folge hatte and damit die Uberlebenschance des Steinkohlenbergbaus in der Bundesrepublik Deutschland enorm verbesserte. Der Grund hierfdr lag darin, daB der Schildausbau im Vergleich zu dem vor ihm eingesetzten Rahmen- and Einzelstempelausbau eine wesentlich hdöhere Ausbauleistung erbrachte, weil er sich weit weniger empfindlich gegen Hangendausbruche and aus dem Alten Mann hereinbdschende Bruchberge erwies. So erklärt sich auch die stürmische Entwicklung and die schnelle Verbreitung des Schildausbaus. Bereits 1975 stammte rd. 50 % der Fdrderung aus Schildstreben, 1990 waren es fiber 75 % and heute sind es fiber 90 %. 1.2 Die Staubentstehung beim Schildausbau Die Erfolge des Schildausbaus sind unbestritten. Jedoch nahmen :nit seiner Einführung die Probleme der Staubentstehung and Staubbekämpfung im Vergleich zum Ein zelstempel- and Rahmenausbau erheblich zu. MaBgebend dafür sind hauptsächlich folgende Gründe: - Abbau von dozen nit gebrächen, weichen Hangendschichten, die erst durch Schildausbau abbaubar wurden, - Zerkleinerung des auf den breiten Kappen aufliegenden Bergematerials infolge der höheren Ausbaustiltzkrafte des Schildausbaus, Zermahlen der sick in die Spaltabdichtungen hineinarbeitenden Bergestückchen, - Erhöhung der Wettergeschwindigkeit infolge der durch die Baufarm des Schildausbaus bedingter. Verkleinerung des Strebquerschnitts verbunden mit der Aufwirbelung and Aussichtung von Staub, - Aufwirbelung von bereits abgelagertem Staub im Bruchraum beim Hereinbrechen der Dachschichten. Die genannten Gründe treten zumeist nicht in jedem Abbaubetrieb gleichzeitig auf. Sie rind vielmehr u.a. abhängig vom Ausbautyp, von den Gebirgsverhältnissen and von der Abbaugeschwindigkeit. Trotzdem ergeben sich beim Vorrücken des Ausbaus in der Regel hohe Staubkonzentrationen, die deswegen besonders kritisch sind, weil es sich um quarzhaltigen Feinstaub handelt, der besonders gesundheitsschädlich ist. Die Hauptzutrittsstelien]

Jan 1, 1984

By G. L. Humphrey

Although silicon carbide has been an important manufacture refractory for many years, knowledge of its thermodynamic values has been seriously lacking. In fact, some of the very properties that make it a useful substance, particularly chemical inertness, obstruct determination of its heats of formation and reaction. This paper reports the results of new measurements of the heats of combustion and formation, low-temperature heat capacity, entropy at 298.16°K., and heat-content and entropy increments between 298° and l,800°K. Two varieties of silicon carbide were studied -the common, hexagonal (type II) and cubic. The data are combined to obtain heat and free-energy-of-formation functions, which are given in tabular form. It is shown that the cubic variety is the more stable at temperatures to at least 1,800°K but, because of the inherent difficulties and errors in the heat-of-formation determinations at 298°K, it was not found possible to specify the free-energy difference accurately. The mechanism of silicon carbide formation from silica and carbon is not known and is not ascertainable from thermodynamic data. It appears improbable, however, that it can be a single-step reaction. Some reactions involving silicon monoxide gas and metallic Silicon, as possible intermediates in silicon carbide formation, are considered and shown to be thermodynamically feasible.

Jan 1, 1952

By Hans Perlid

In the handling of emulsion explosives pumping is a key operation. A number of serious accidents has shown that pumping can be a risky operation and should be carefully considered and investigated. This is the background behind a series of pump tests carried out by NITRO NOBEL.

Jan 1, 1996

Study on Influence that Styrene-Phosphoric has on the Surface Property of Rutile Minerals

Sep 13, 2010

By P. N. Vernon

Ausmelt top entry submerged lance technology offers a cost-effective means of carrying out a range of base metal smelting operations with minimum impact on the environment. The system is capable of using a range of fuels depending upon local costs. Due to the intense, localised reaction zone, high energy efficiency is obtained and the physical size of the plant is relatively small compared to that of most competing technologies. Capital cost can thereby be minimised. The furnace is well enclosed, such that fugitive emissions and ingress of diluting air to the gas stream are both minimised. The oxygen potential in the slag can be varied over a wide range such that the system can be applied in both oxidising and reducing duties. Following a general description of the technology, the paper discusses Ausmelt plants already in operation. The application of the technology for the provision of additional smelting capacity, for the improvement of converting operations and for slag cleaning is then described. A brief explanation of how these processes could be applied at southern African smelters is given and the paper closes with an assessment of novel Ausmelt applications for this geographical region, such as zinc recovery from sulphides.

Jan 1, 1997

By A. D. Dalvi

With the current economic situation, the demand for nickel and other base metals has fallen significantly. More than 440 kt/yr world nickel capacity has been taken out of production within the last year, or more than 25% of the total [1]. This situation is similar to that at the end of 1970?s and it will take a number of years for the demand to recover to the levels before the economic downturn. In the meantime, the challenges facing the industry have increased due to diminishing ore grades, more inaccessible and complex deposits, mounting capital and operating costs and the various external pressures which include socio-economic, environmental, and energy challenges. All industries will be faced with paying the ?total ownership costs? in the future. This will only increase the burden on the industry. How to cope with this in what Thomas Friedman calls the ?Energy-Climate Era? [2] will be the most pressing challenge for the next generation of metallurgists and managers. It will force us to take a broader view of the problems and the solutions beyond mere technical. The metallurgists, engineers and project managers will have to look at the overall projects and their objectives in designing the solutions, requiring a top-down strategic approach.

Jan 1, 2009

By Robert A. Jankowski, J. Harrison Daniel, Fred N. Kissell

Introduction Longwall coal mining in the US has steadily increased since its introduction in 1960. There are now 108 systems operating. (Sprouls, 1986). Advantages of longwall mining include higher productivity, improved safety, and greater coal recovery. Respirable dust, however, is one of the more serious obstacles to realizing the full potential of longwall mining. Early in 1980, the US Bureau of Mines (USBM) initiated extensive in-house and contract research to identify and evaluate effective methods of controlling respirable dust exposure of longwall face personnel (Niewiadomski, Jankowski, and Kissell, 1981). It was found that several control procedures must be combined to assure compliance, using control techniques appropriate to the dust source. These techniques can typically be grouped into the following categories: reduction of dust generation; dilution of dust; capture or knockdown of dust; and dust avoidance. Control techniques can be divided into basic and effective dust control techniques; additional necessary controls; and optional supplementary controls. This information should allow longwall mine operators to select control methods applicable to their particular operations and to develop a dust control plan that meets Federal dust standards. Basic and effective dust control techniques There are three basic dust control techniques (Taylor and Jankowski, 1982) that should be implemented on all longwall mining operations. • A passive barrier or external water spray system design that confines shearer generated dust near the face and away from the operators. • Large quantities of water through the sprays, particularly the drum sprays, to aid in dust knockdown and prevent dust becoming airborne. • A cutting sequence that allows the shearer operators to work primarily on the intake-air side of the lead cutting drum. Shearer clearer There are some poorly designed shearer-mounted spray systems with nozzles directed upwind at the cutting and loading zone of the intake-side drum. These actually carry dust away from the face and upstream of the drum. Where, it mixes with the clean intake air (Fig. la,) and is carried out into the walkway over the shearer operators. The Bureau developed a novel shearer spray system, called the shearer clearer. It takes advantage of the air-moving capabili-

Jan 10, 1986

By J. G. Davis

The St. Peter Sandstone is typically a well-sorted, friable, ultra-pure, fine- to medium-grained, quartzose sandstone with silica content higher than 99 weight percent in places. The sand grains are well-rounded, highly spherical and characteristically frosted. Their size typically varies from 2 millimeters diameter (No. 10 U.S. Standard Sieve Series size) to less than 0.08 millimeters diameter (No. 200 U.S. Standard Sieve Series size). A freshly exposed surface of the formation is commonly white with shades of pink and green. Weathered surfaces are a dirty gray or brown and are case-hardened at many localities. Bedding is characteristically indistinct, and the formation usually appears massive throughout. The rock is cross-bedded and ripple-marked locally. The formation is generally porous, permeable and rarely fossiliferous in Missouri. The St. Peter is continuously present in the subsurface in the northern half of the state and along the southeastern edge of the state. The St. Peter crops out in a narrow band that starts in western Montgomery County and runs southeastward, along the Missouri River, to just west of St. Louis and continues south, just west of the Mississippi River, through Scott County. The outcrop belt varies from less than one mile wide to over ten miles wide, and it is over 150 miles in length. The formation dips into the subsurface radially away from the outcrop band. A notable isolated outcrop occurs in Lincoln County to the north of the main outcrop band. The St. Peter is discontinuously present in the subsurface along a band in the west-central portion of the state. It is not present at the surface or in subsurface in the remainder of the state. The formation averages 80?100 feet thick. There is an estimated 3.8 trillion short tons of St. Peter in Missouri. Sieve analyses on drill cuttings indicate three subsurface locations in northeastern Missouri where the St. Peter is greater than 10 percent by weight of sand falling in the 20?40 U.S. Standard Sieve Series size range. The St. Peter was first produced in Missouri in the 1870s for the manufacture of glass. Since that time it has been used as a paint additive, filler material, polishing compound, filtering media, and recently it is commonly used as a fracture proppant in oil and gas wells. The St. Peter is currently quarried and produced in Missouri from four sites located in St. Louis, Jefferson and Perry counties. In the same area there are at least nine abandoned historic mine sites.

Feb 27, 2013

This paper addresses the methodology of introducing risk into the development of mine plans for open pit mines. Recommendations are put forward for achieving a risk balance between mineral resource estimates and slope design. A design process identifying criteria for different stages of planning is presented. Business risk is separated from geological/geotechnical risk and procedures to address these within the development of mine plans are suggested. It is concluded that a formal design process improves communication between key decision makers and adds value to shareholders, investment.

Jan 1, 1997

By Larry Stearns, Lori Tiefenthaler

Remediation of contaminated soil represents a significant market for application of Deep Soil Mixing (DSM). Eighty-one percent of U.S. Environmental Protection Agency (EPA) Superfund Program’s site remedies have involved contaminated soil. Contaminated soil is frequently treated by In-situ Solidification/Stabilization (ISS). ISS treatment of contaminated soil involves mixing binding agents into soil using DSM techniques. DSM is a core business for many DFI members. Members may improve and broaden their services to clients by learning about the recent ISS treatment of contaminated soil at a Superfund site. ISS treatment is part of the EPA-selected remedy for a Superfund Site in the metro New York City area. The property has seen heavy industrial use for more than a century. Soil at the site is contaminated with a variety of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) including coal tars and heavy metals, principally arsenic and lead. Beginning in 2017 and continuing through 2018, approximately 150,000 cubic yards (115,000 cubic meters) of soil will be treated by ISS at the case study site. Portland cement and slag cement are mixed into the soil by DSM techniques using GPS guided excavators to immobilize the hazardous constituents within the treated soil. ISS treatment by DSM will contribute to redevelopment of this valuable property. This paper will describe ISS constructability and performance, case study grout mix design with geotechnical results for strength and permeability, and deep soil mixing techniques. INTRODUCTION In-situ solidification and stabilization (ISS) is a deep soil mixing (DSM) technique applied in the environmental remediation field to physically encapsulate, or chemically bind, contaminates of concern such that the impacts to human health and the environment are mitigated. Common remediation applications of ISS include mixing cementitious reagents into contaminated soils to form a monolithic mass with desired performance characteristics, and the installation of vertical subsurface walls designed to control groundwater movement. A key characteristic of ISS is that the contaminated soils are treated in their existing location at the project site and then are left in place after treatment. Typical performance characteristics of the ISS treated soils include improved unconfined compressive strength (UCS), reduced hydraulic conductivity (HC), and reduced leaching potential of soil contaminants. Increased shear resistance of the treated soil may also be a performance requirement where seismic loading is a concern.

Jan 1, 2018

By Charles M. Mason

The Bureau of Mines evaluated equipment and procedures for drop-weight testing of explosive liquids as prescribed by Test 4) a widely used method. It was demonstrated that partial ignitions, originally designated as negative results, should be designated positives; it was also shown that wear or erosion of the sample cups and the type of mount used for the apparatus had important effects on the results. Relative sensitivity as measured by Test 4 was found to vary slightly with temperature. The Bureau also designed a fixed 2-kg weight and associated electromagnetic release, which subsequently were incorporated as standard in a revision of Test 4. The original concept that the test involves only adiabatic compression was found to be an oversimplification; an alternate mechanism for the initiation process is proposed in which due consideration is given to the effects of cavitation and microjets.

Jan 1, 1966

By Kevin Bell

About Beltek Inc. For more than a decade Beltek, Inc. has been working with national and international organizations to harness and deliver solutions which gain real ebusiness advantages in today's world. Our objectives are to partner with our customers to achieve maximum results, while reducing costs. At Beltek, we provide a commitment to you and your organization's needs. Whether that be delivered by ensuring our services and products are state of the art or by providing a level of personalized service, which makes you feel like the center of attention, Beltek is about adding value to every job we work on. The individuals who work at Beltek quickly become your friends because we share your passion and enthusiasm for the business we are in. That's why every person is a leader in his or her respective fields. Having these individuals as apart of our business ensures you get the best out of our equipment, receive the very latest in advise, problem solving and support. We also pride ourselves on our ability to remain flexible at all times because we know deadlines and schedules can change quickly, so we always go the extra mile to deliver exactly what you need.

May 1, 2004

By L C. Pretorius

Pipe pigging is a technique for the in situ (field) coating application, to create a seamless internal anti-corrosive lining of long pipelines. The technology originated in the cleaning of pipes, and these proven cleaning methods continue to be used today. Firstly mechanical cleaning of the pipeline is performed, using wire brush, razor back, course stud and fine wire pigs, then foam pigs, or criss cross pigs, and urethane blade scrapers to remove loose debris, wax, residual hydrocarbons and corrosion products from the pipeline. Part of the proprietary techniques and expertise is to ensure that these cleaning pigs do not get stuck Next chemical cleaning of the pipeline is performed, using repeated pig runs with detergents, solvents, acid etching, corrosion inhibitors, consecutively batched between two pigs, to ensure a clean, dry metal finish to a visual cleanliness standard of ISO SA2½. These in situ techniques were developed, 40 years ago to apply internal corrosion protection to pipes using a thin layer of epoxy based paint (50 to 100 micron). Until recently these old techniques were never improved upon. Although many thousands of kilometres of pipes were successfully coated with these thin film epoxy based paints and old application techniques, these thin paint films had problems in weld coverage, and were also unable to fill pits caused by pitting corrosion, and unable to replace metal loss caused by channel erosion. New coating material developments, revised application methods and modified pigging equipment have now made it possible to apply thick film coatings as corrosion barriers to the internals of pipes in the field, using these pigging techniques. The thick coating films can be up to 1 mm (40 mils) thick in a single coating run over long distances. The new thick film coating materials and application techniques are similar to continuous screeding, creating a far more robust seamless internal pipe lining when compared to the old technology of thin film paints. With thick film polymers the option now exists to create a structural GRP pipe within a pipe, be it steel or cementicious. It has been preferable, even necessary, to move away from the traditional epoxy paints and coatings. It was found difficult or impossible to use epoxy materials for these pipe coating applications due to the requirement for achieving a suitable viscosity with adequate hold up. In order to reduce epoxy viscosity a solvent or reactive diluent is required. This inevitably lead to solvent entrapment and poor cure characteristics in cold climates. Further mud cracking in over thick areas, the inability to extend or reduce pot life, poor control of cure time and limited resistance to aggressive or chemical environments made solvent based epoxy resins a poor choice.

Jan 1, 2006

By T. Grammatikopoulos, A. McKen, O. Christiansen

Vanadium mineralization occurs in oxide-rich horizons within layered metagabbro zones of the Sinarsuk deposit, West Greenland. The main oxide minerals are vanadiferous magnetite and ilmenite, comprising 30% to 90% of the rock volume and the ratio of magnetite to ilmenite ranges from 3:2 to 4:1. Ore microscopy shows that magnetite and ilmenite vary between 0.2 mm and 4.5 mm in grain size, but locally they are coarser grained. Grains are subhedral to euhedral and annealed suggesting that they will liberate very well upon grinding. Electron microprobe analyses indicate that magnetite grains are homogeneous and have a vanadium content, in different mineralized samples, ranging from 1.93 wt% to 2.68 wt% equivalent V2O5. Ilmenite hosts abundant and variably sized hematite lamellae, and it has vanadium contents ranging from 0.32 wt% to 0.59 wt% equivalent V2O5. Preliminary beneficiation of two composite bulk samples shows the samples can be beneficiated fairly easily using low-intensity magnetic separation at a coarse grind (106 microns to 600 microns) to yield a vanadiferous magnetite concentrate. The presence of hematite lamellae in ilmenite prevents recovery of a satisfactory ilmenite concentrate. The most likely beneficiation flowsheet would encompass a primary mill (SAG or rod mill), which would grind to about 600 microns, followed by a rougher magnetic separation stage. The rougher magnetic concentrate would be reground in a ball mill until suitable liberation is achieved. The reground material would then be cleaned in further LIMS stages. However, further laboratory testing is required to establish the final beneficiation program. This work demonstrates the value of mineralogical investigation in guiding and explaining the results of beneficiation processes.

Jan 1, 2002

By A. W. Ruff

The seismic wave produced by an explosive is very important in blasting. A true understanding of the wave is only important when considering possible structural damage to buildings located near the blast, but it is also of primary importance when considering rock fragmentation. Because of the importance of the seismic wave to fragmentation, a finda-mental study of the seismic wave and its effect was made at the Cananea Consolidated Copper Co.'s mine at Cananea, Sonora, Mexico. Strain gages were used to measure the strain in the rock when nearby explosive charges were detonated. The variance in the circuit voltage caused by changes in the resistance of the strain gage was measured with an oscilloscope and recorded with a Polaroid camera. CONFINED DRILLHOLE CHARGES To record the seismic wave from a confined drillhole explosive charge, a gage was cemented to the bottom of a 4-in diam drillhole. The horizontal gage hole and nine horizontal charge holes were drilled perpendicular to the center line of the 2-39 drift and 4 ft above the floor. The gage hole was 29 in. deep, and the charge holes were drilled so that each bottomed 1 in. deeper than the gage hole. The gage was installed with its axis horizontal and parallel to the 2-39 drift. The charge holes had the following horizontal distances from the gage: hole 3, 3 ft; hole 4, 4 ft; hole 5, 5 ft; hole 9, 9 ft; hole 10, 10 ft; hole 14, 14 ft; and hole 15, 15 ft. Figs. 1 and 2 show the relationships of the gage and the charge holes. Charges of 80 pct special gelatin, which weighed 50, 100, and 150 g were exploded in the charge holes and the seismic waves were recorded. All charges were stemmed with 200 g of mud and detonated with an electric blasting cap. Fig. 3 shows the recorded seismic waves. The reflected components of the waves were too weak to be objectional on these records. Table I shows the data taken from the wave forms. The approximate average velocity of a wave with a 9-ft travel distance was 12,900 fps. Since different charge weights were used, it was necessary to scale the data. The scaled maximum compress ion-strain data and the scaled maximum tens ion-strain data are shown in Figs. 4 and 5, respectively. Figs. 6 and 7 show the strain-distance data from Figs. 4 and 5 converted to a 1-lb charge. The results showed that the wave consisted of an initial compression pulse followed by a tension pulse. The amplitude of the tension pulse approached the amplitude of the compression pulse as the distance between the gage and the shot increased. The decay rate of the seismic wave is very important in the evaluation of the blasting characteristics of a rock. When high-amplitude stresses are produced, as in rock fragmentation, the rate of decay is much more rapid than when small amplitude stresses are produced. In underground mine blasting, the burdens are usually not greater than 6 ft and the decay is very rapid. The rapid seismic-wave decay rate in the fragmentation range means that in practice, if the minimum weight of powder is used to break a specified burden, only a very

Jan 1, 1961