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By George E. McCormack

At the time of my visit to the Peoples Republic of China I was employed by the E.I. DuPont Company as a Technical Specialist in the Explosives Department. The purpose of my visit was to observe the use of explosives in mining and tunneling in a coal field 500 miles south of Peking near Hsu Chou in Kiang Su Province. The DuPont Company was preparing a proposal for the sale of a Tovex water gel plant to the Chinese Government.

Jan 1, 1982

By H. M. Friede

Iron Age metal working in the Magaliesberg area by H. M. FRIEDE, Ph.D. (Visitor) Evidence of smelting and metal working in the Magaliesberg comes mainly from three sites: Broederstroom (Pretoria District). Uitkomst Cave (Krugersdorp District), and Olifantspoort/Olifantshoek \Rustenburg District). The analyses of copper ores found at or near these sites are reported. as are the analyses of twenty-six samples of slag from the Magaliesberg area and other sites in the Transvaal. Iron implements and copper ornaments found at the Magaliesberg sites are described. and the analyses of some of these specimens are reported and discussed. A metallographic report on two iron objects from Broederstroom points to similarities in the smelting and forging techniques that were practised in the Transvaal and Nigeria during the Early Iron Age.

Jan 6, 1977

By Mike S. Ness, Allan G. Provost

High speed drilling, mucking, and hauling equipment was used in driving approximately 2.16 km(7100 ft) of lower power tunnel in quartz diorite for the Tyee Lake Hydroelectric Project near Wrangell, Alaska. The .91 m(36 in.) guage rail mounted equipment included a Tamrock 2-boom electric/hydraulic drill jumbo, a Haggl and 8HR mucker , and 3 Hagglund 115C shuttle cars. Several other innovative techniques allowed maximum advance rates of up to 17.5 m/day(57ft/day) in the 3 m(10ft) horseshoe section. Average tunnel advance was approximately 11 m(day(35.4 ft/day). The primary difficulties preventing full utilization of the equipment potential were the operators' "learning curve", the need for complete retraining of all personnel in the new methods, and minor sections of faulted ground.

Jan 1, 1983

By Jeffrey W. Nelson

Predictions of creep closure for periods ranging up to more than 1,000 years are needed for designing a radioactive waste repository in a salt formation. Such long-term predictions must be based on the use of laboratory and field test results extrapolated by numerical modeling. Laboratory test results are presented which show highly variable creep behavior for salts from different sites as well as salts from the same site. Comparisons of measured creep closures against predicted closures are presented for two deep boreholes in Louisiana salt domes and for an exploratory shaft and drift in southeastern New Mexico bedded salt (WIPP). These data illustrate the significant uncertainties involved in long-term closure predictions and indicate the critical need for site-specific, in situ closure measurements over extended periods of time for repository design.

Jan 1, 1984

By N. Arbiter, J. Steininger, C. C. Harris

Power consumption and operating variables in air-liquid systems for a wide range of operating conditions in the turbulent region have been correlated by two dimensionless groups involving the power ratio and the flow number. The form of the correlation was developed by considering flow balances related to the air-liquid composite density in the impeller zone. Data for two phase air-liquid systems, both from literature and from the present investigation, has been correlated with high statistical significance. Two phase solid-liquid and three phase gas-liquid-solid systems have also been correlated. The quantification of power requirements in the agitation of liquids is well established.1 Rushton, Costich and Everett have shown that, for mixers operating in the fully turbulent region with no vortex, the power number

Jan 1, 1964

By John A. Mavrogenes

The Texaco gasification system developed at the Monte Bello pilot plant efficiently bums petroleum-coke thereby producing syn-gas and electricity. This system produces more electricity than conventional burners, yet the only by-products are pharmaceutical grade sulfur and V -rich slag. Vanadium is known to exist in multiple valence states in compounds which possess a wide range of melting points and physical properties. Consequently, it becomes important to carefully regulate oxygen fugacity throughout the system in order to control vanadium valence state. Vanadium phase equilibria is presently poorly understood, in large part because of the multiple oxidation states of vanadium (-I, 0, +2, +3, +4, and +5) and the difficulty of unequivocally identifying the valence state(s) in many compounds. The operation of these gasifiers at approximately 1400°C is well above the melting point of V20S but considerably below the melting temperature of V02 and V 203. If J02 can be regulated to keep the burner within the V 205 field, slag material would more likely remain molten and more easily flow out of the bottom of the burner. In pure V oxides. the oxidation state is readily determined by microprobe analysis. where V20S (V+5) is 56% V, V02 (V+4) is 61.4% V, and V203 (V+3) is 68% V. However, V valence in multi-element phases (especially phases containing other elements of variable valence) cannot be resolved by microprobe analysis alone. Petroleum-coke gasification slags collected from within the gasifier under different oxidation conditions were studied by electron microprobe analysis (EMPA). X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman spectrometry in conjunction with microprobe analysis was found to resolve the valence of vanadium in the phases of these slags. Raman spectra collected from homogeneous single phase V-oxide standards in vacuum at low temperatures (-150°C) yielded peaks characteristic to each valence state. Gasifier slag samples are, however, much more complicated. Oxidized samples contain: fine grained (Ca. Mg, Fe. V) oxide matrix of variable composition, (Fe. V, Ni) spinel. (Fe, AI, V, Ni, Mg) spinel, V205laths, AI-Si glass blebs and Ni sulfides. Reduced samples contain: crystalline Ca-siIicate matrix, subhedral to euhedral (V, Fe, Mg, AI) spinel, subhedral V02, Fe and Fe-Ni sulfides, Fe-Ni alloys, and complex Ca-oxide matrix. The different spinel assemblages, the characteristic V-oxides and the distinctly different character of the matrices makes the oxidized and reduced slags readily discernible.

Jan 1, 1995

By H. G. HYMER

B ECAUSE of its remote geographical position and inaccessibility, little is generally known of the mining and prospecting in Northern Rhodesia. In this rather new and promising region, the development of mines presents many difficulties. Although many mineral discoveries have been made, progress in .prospecting the huge mining concessions has been handicapped by the lack of roads, communication, transportation, native population and incomplete knowledge of geology.

Jan 1, 1929

By David Mitchell, Daan Delport, Frik Marx, Mike Shapiro

The use of copper cooling elements to enhance refractory lining life in pyrometallurgical vessels is common in modern furnace design. Copper elements typically incorporate a base panel with cast in cooling passages and an integral extended surface (formed of pins, fins or similar) onto which suitable refractory material is cast. The metallic, conducting parts are located towards the cold face of the lining, with the refractory material interposing between the coolers and the process. The coolers are designed to arrest wear of the refractory material by freezing a layer of slag or partially reacted material onto the hot face, thereby rendering the lining inert to further attack [1]. These coolers have achieved success in new furnaces and relining of existing vessels. The freeze layer is prone to mechanical damage during operational and process instability. The coolers must be capable of extracting the additional heat flux under upset conditions to facilitate rapid self-repair of the freeze layer and prevent further refractory wear in the intermittently exposed areas. However, operational experience has shown that the high heat flux capabilities of the copper coolers have some disadvantages, especially in processes producing vapours which form corrosive compounds when condensing onto the cold surfaces of the coolers. When corrosive conditions develop, the entire composite will fail due to loss of structural integrity, and as a result of leaks from the cooling water passages. This paper describes recent developments in the approach to the design and manufacture of copper cooler panels customized to achieve specified heat fluxes and temperature profiles, thereby reducing the formation of corrosion mechanisms in applications with corrosive gaseous environments and enhancing refractory lining life. Condensation formation prevention is achieved by adjusting the geometry of the cooler and selection of suitable materials of construction.

Jan 1, 2007

By Dena Morgan, Emre Biringen

"Abstract This paper discusses the execution of pile installation and design issues at two environmentally challenging industrial sites in North America. Environmental regulations set constraints on the design and require versatility in choice of technology.For a proposed bridge, due to protected fish habitat, performing soil borings within 30 m of the creek embankment was prohibited. The limited subsurface profile indicated a thick upper layer of granular material, thus driving H-piles was considered. However, to limit generation of vibration and noise in the protected area, drilled piles had to be used. During execution, the subsurface profile differed from that in the borings 30 m away. Very soft, saturated silt was encountered at the bottom of the caisson and the length had to be redesigned very quickly while the contractor waited for instruction. For a new structure in uncontrolled fill area, performing soil borings was not allowed. It was known that a layer of peat was present in the area, but no information regarding the thickness and extent. The subsurface profile generally consisted of granular material overlying a thick compressible silt layer. Somewhere within the granular layer peat would likely be encountered. Franki piles were chosen to penetrate the peat and bear in the underlying granular material. During environmental sampling in the area, methane gas was encountered and Franki piles were no longer a viable option due to safety concerns. The foundation system was changed to steel H-piles driven to bedrock, which was more than 50 m below the ground surface and sloping. Rock shoes that would work to significant slopes had to be used in order to increase the likelihood of good embedment within the bedrock. Also, due to obstruction of an approximately 3 m thick debris field that was encountered in the upper granular soils, some of the piles had to be relocated and extra piling needed to compensate for such differences. The results of PDA testing to estimate compressive capacity and a series of lateral load tests are presented.INTRODUCTIONThe design issues that are encountered during construction can be quite problematic and have a significant impact on schedule. In order to avoid such impact on the project, a thorough subsurface investigation should be considered prior to design and construction. Better understanding of environmental regulations also prevents costly changes to the foundation design. This paper discusses the execution of pile installation and the design issues at two environmentally challenging sites in North America.BRIDGEDuring the subsurface investigation for a proposed industrial building complex, several boreholes were drilled within the footprint or in close proximity of various structures, with Standard Penetration (SPT) sampling of the upper coarse-grained soils (sand/gravel) and undisturbed sampling of the lower fine-grained soils (silt/clay). The SPT blow counts (N60) were corrected by a factor of 1.35 in order to incorporate the SPT automatic energy transfer ratio. When Modified California Sampler was used, a correction factor of 0.44 to 0.64 was also applied. N60 values were further corrected for gravel to avoid artificially high blow counts during the analyses due to spoon samples contact with gravel and cobbles, and the corrected values of (NG)60 (limited to a maximum value of 50 blows/300 mm) were used for design. The information from the SPT boreholes was then used to assess the subsurface conditions beneath the structures, as well as for a nearby bridge that was designed to cross over a creek. Since performing soil borings within 30 m of the creek embankment was prohibited due to the protected fish habitat, the investigation with regard to the bridge abutments was limited to two deep boreholes (B10-33 and B10-34) at the bridge location and two additional boreholes (B10-35 and B10- 36) located approximately 200 m upstream. The bridge location and two sets of boreholes are"

Jan 1, 2014

By L. S. Kolbert, C. H. Baab

Introduction In June 1981, the Electric Power Research Institute (EPRI) issued a report titled "Control Systems in Coal Preparation Plants" to determine the status of instrumentation and automation systems in the coal preparation industry. EPRI concluded that the control systems presently being employed in the US coal preparation plants "are relatively primitive compared with those in other mineral processing industries; and analytical instrumentation is virtually non-existent." With tighter specifications on the quality of steam coal, interest is increasing in more sophisticated control systems. One type of device that is currently assisting the preparation plant operator optimize and control the coal cleaning process is nuclear based instrumentation. Nuclear instrumentation includes methods for measuring weight, level, and density as well as for performing elemental analysis on coal. Major Features and Benefits of Nuclear Measurement and Analysis Systems There are many features and benefits of nuclear instrumentation. The major benefit is that nuclear instrumentation is non-contacting. The measuring heads do not contact the process materials. This enables measurements of corrosive, abrasive, or high temperature materials with no loss of performance, reliability, or useful life. Also, there are no moving parts to wear or be fouled by dust or corrosion. Installation is simple and inexpensive. For instance, density gauges are simply clamped onto existing pipe runs. Weigh scales and level switches usually require nothing more than welding brackets to customers' equipment. Once installed, routine maintenance can be performed without interrupting the process. Thus, nuclear instrumentation is highly reliable and easily installed and maintained. The operating life of the instrumentation is virtually unlimited. Principle of Operation Nuclear belt weigh scales, point level switches and density gauges all operate on the gamma-ray transmission principle. A beam of gamma radiation from a radioisotopic source is projected through the process material either on a belt, in a vessel, or in a pipe. Opposite the source is a radiation detector whose electrical output is proportional to the intensity of the radiation it absorbs. Gamma radiation is part of the same electromagnetic spectrum that encompasses light, infrared, and x-rays. In many respects, gamma radiation behaves much like light. However, it is far more penetrating and can be transmitted through considerable thickness of materials that are opaque to visible light, e.g., several inches of steel. Types of Nuclear Instrumentation in Coal Preparation Plants There are four types of nuclear instrumentation presently being employed in coal preparation plants. They are: •Belt Weigh Scales •Point Level Switches •Density Gauges •Coal Analysis Equipment. Each type of instrumentation has a number of potential applications within the plant. What follows is a discussion of three different types of devices and their applications. Weigh Scales In coal preparation plants, weighing instruments are used for measuring material throughput, totalized weight, and batch weight on conveyor belts and other transport equipment. They are also used on drag chain conveyors, vibrating conveyors, and screw conveyors. Weighing is important for receiving the run-of-mine coal, controlling mass flow, scheduling production, and loading and shipping the washed coal to market. There are two basic types of weighing instruments: gravimetric and nongravimetric devices. Gravimetric devices are units which measure the pull of gravity on the material being weighed. Nongravimetric devices are not dependent on the force of gravity on the sample. Nuclear weigh scales are the most prevalent nongravimetric devices used. The nuclear weigh scale works on the same basic principle as other nuclear gauges. The greater the quantity of material placed in the path of a radiation beam, the more radiation will be absorbed by the material. In weigh scales, Cesium 137 source is generally placed above the moving stream of material so that the radiation is directed through the material. An ion chamber radiation detector is on the opposite side of the material. The radiation passing to the detector generates a signal which is inversely proportional to the weight of the material present. This signal is amplified and integrated with the speed of the process flow yielding the weight. The weight is indicated and can be totalized for throughput, batch control, etc. In conclusion, radiation weighing methods have become well established in the coal preparation industry throughout the world. As mentioned before, this device finds its most

Jan 1, 1985

By David W. Kennedy, Stephen P. Harrison

In the past few years, a new system has been developed for ventilating longwall panels in some gassy coal mines in the Northern West Virginia area. This system utilizes a five or six foot diameter air shaft to ventilate a group of three or more longwall panels dependent on conditions. This shaft exhausts all the air needed to, ventilate the active longwall and adjacent gob areas. By law, this bleeder fan can handle double the maximum methane concentration allowed in a normal return air course. As a result, the methane that must be diluted by the primary ventilation circuits is reduced. This new ventilation system was first conceived by mine management as a means of coping with a sudden shift in production mode that occurred a few years ago. Formerly, production often consisted of room and pillar mining with continuous miners. The high methane liberation rate was handled by driving entries around a large block of coal prior to mining. This isolated the future mining area from the adjacent coal seam and allowed a major portion of the trapped in situ methane to bleed off. Also, these bleeders served to exhaust return air from the mining area. Once the bleeders were established, productive mining could start. When the decision was made to shift production mode from continuous miners to longwall mining, some of the bleeders did not encompass large enough unmined areas under the old ventilation system to initiate longwall production. Also, many other established continuous miner section bleeders were either improperly positioned or too restricted for longwall ventilation. Unfortunately, standard bleeder development can take up to two years' time. In order to eliminate the old style bleeder system and maintain or increase the margin of safety for ventilation, the bleeder shaft system was conceived. With this system, the only entries developed are those necessary for the longwall, significantly reducing the production delay. In this area, the Pittsburgh #8 coal seam dips to the northwest. As a result of this dip, the bleeder shaft is constructed in the northernmost set of tailgate entries. In this manner, groundwater accumulations can be pumped to the surface and bleeder entries kept dry. During the initial longwall entry development, the bleeder fan can be used to ventilate entries adjacent to virgin coal where significant methane liberation often occurs. Once longwall production starts, the bleeder shaft exhausts the entire air quantity necessary to safely ventilate the longwall. As the bleeder entries deteriorate, the air quantity and pressure characteristics must be increased. The extreme flexibility of the centrifugal fan used at the surface allows the air quantity and pressure to be adjusted without stopping the fan. This improves safety by decreasing the possibility of a methane buildup resulting from the fan being out of service. The bleeder shaft system of ventilation, developed by mine management in Northern West Virginia, can provide a safe means for effectively ventilating longwall panels in excessively gassy mines. This system should be considered where mining conditions are comparable.

Jan 1, 1982

By F. C. Araújo, T. Tavares, J. Leite

"This work presents the small-scale mining cluster of kaolin in Rio Grande do Norte (RN) and Paraiba (PB), both Brazilian states, including the following information: number of companies, process flowcharts, production numbers, mineralogical (XRD) and chemical (XRF) composition, granulometric distribution (screen and laser granulometer) and image analysis (SEM). Some social indicators in the region of the RN and PB States are presented in association with these data. The number of companies and their flowsheet were obtained through in situ visits and sample collection for technological characterization. The comparative study of the different flowsheets for kaolin production in the world was done using the databases and presenting the state of the art of kaolin processing. The results indicated that the mean feed typically contains 35-39% kaolin with quartz, muscovite and kaolinite as main mineralogical components and SiO2 (65.83%), Al2O3 (21.19%), K2O (3.9%), and Fe2O3 (0,63%) as main chemical constituents. The products of mineral processing are twofold, one between 74 µm and 37 µm, and the other smaller than 37 µm. The wastes of operation had major quantities of kaolin. The average Human Development Index (HDI) of the cluster region is approximately of 0.61, which shows an association between mineral processing plant and social indicators. The kaolin recovery, however, is between 30-55% for the three most common types of flowsheets that are currently used in the small kaolin mining cluster, indicating a need for technological improvement to achieve regional development. These data could be used incrementally to adapt the process plant currently used in the small-scale mining cluster of kaolin."

Jan 1, 2014

By G. S. Scott, W. J. Huff, G. W. Jones, R. E. Kennedy

"INTRODUCTION This report gives preliminary results of field and laboratory investigations made at the request of the War Production Board relative to causes that have occurred during the last 8 months in acetylene-generat72,r plants in shipyards on the Pacific coast.Six acetylene-generator explosions have occurred in four shipyards. These explosions killed five operators, injured six others, and extensive damage to the plants involved and curtailmnent of vital defense Although the occurrence of acetyiene-generator explosions in other section of the United States is not known, it appears, at least, that if such have occurred, they have caused only minor damage and no loss of lives.The use of acetylene in shipyards on the west coast has expanded tremendously during the past 2 years. These shipbuilding, companies erected aletylene-generatcr equipment, which was soon found to be entirely inadequate to meet the needs of their expanding acetylene requirements for welding, cutting, shrinking, and other purposes, and instances found it necessary to operate their equipment at rates greater than deemed consistent with safe operating practice."

May 1, 1944

By V. G. Mooradian, John T. Norton

THE diffusion of metal atoms into the crystal lattice of another metal and the assumption of regular positions to form a homogeneous alloy are some of the most fundamental phenomena of structural. metallurgy. The mechanism of this process has been the subject of a great deal of study from many viewpoints, but the picture is still far from complete. It is generally believed that if one metal is to diffuse into another, the first must have some solubility in the second1. This means that the solvent must be able to accommodate the stranger atoms, either on points of its own lattice or in the interstices between, without losing its own crystallographic identity. It is also a general observation that cold-working is a distinct aid in the diffusion process, causing it to take place with greater rapidity at the same temperature or with the same speed at a lower temperature. There is considerable doubt, however, as to the real significance of the deformation in its effect on the diffusion mechanism. Several factors associated with the cold-working. may be responsible for the increased diffusion rate. The plastic deformation causes a distortion of the solvent lattice, which may be an aid in the assimulation of atoms of another kind. There are many references2 in the literature that suggest that some distortion or "loosening" of the lattice is necessary for atomic migration and that diffusion cannot take place in the undis-

Jan 1, 1935

By John V. Beall

Copper production in the. United States in 1972 amounted to 1,658,000 tons according to the USBM. This figure is up over 1971 but falls below 1970 production of 1,719,101 tons. This report is essentially about the status of copper mining operations in the U.S. and is an update and expansion of the report "Southwest Copper-A Position Survey" published in [A=], October 1965. At that time, the trend was toward using larger equipment to mine lower grade ore and toward the expansion of dump leaching practice. That trend continues today but, it is overlain by intensive activity to comply with existing environ¬mental legislation and uncertainty over proposed revisions of venerable laws governing mining. In the U.S. today there is, practically speaking, no excess smelting capacity so that expansion of copper production through the startup of new mines is inhibited. Owners of a large undeveloped orebody would have to decide before going into production whether to sell the concentrates offshore, which has many problems, whether to try one of several unproved chemical processes for producing refined metal from concentrates or embarking on the construction of a traditional pyrometallurgical plant in the face of considerable uncertainty over the pollution standards that eventually must be met. The situation is such that not only is the present rate of U.S. copper production threatened but the ability to meet projected increased demand in the years ahead may have been severely retarded.

Jan 4, 1973

By Richard Moldenke

The author discusses some economic conditions which have made the career of the cast-iron pipe industry in the United States a checkered one. He next describes the two new developements in the manufacture of cast-iron pipe-both along the lines of centrifugal casting. The advantages and disadvantages of both processes are presented in some detail. Finally, statistics on the production of pipe in the United States at the present time are given, as well as the plants-and their capacities-so far as these are situated in the South. No SINGLE branch of the foundry industry has been brought to a production basis of huge tonnage, low manufacturing cost, and producing material of a remarkably high quality, as has the making of cast-iron pipe. The pipe shop is an excellent illustration of the fact that repetition work in specialties leads to mechanical equipment and manipulation that lower production costs to an. astonishing degree. Hence cast-iron pipe, in dull times, has been sold at a few dollars a ton over the selling price of the pig iron used. On the other hand, these same pipe, shops make fittings .of many varieties, and in much smaller quantities, where the cost is high, and when pipe may be sold, say, at $50 a ton, the fittings on the same shipment will be sold for nearly double that price. The history of pipe-making, in the United States, is a checkered one the mortality of plants is high and, from the nature of the industry, plants must be large to live. In spite of the fact that the best processes must be used to turn out this rather strict specification material, pipe is easy to make and a pipe plant is more of a tonnage mill than the really high-class specialty foundry it should be. Every time, therefore, that the demand for pipe is strong new shops spring up, only to close when the demand has ceased, but the financial damage to the more permanent plants has been done. Both the South and the North have had abundant experiences of this kind, and when recently a northern Public Service Corporation gave its order to France, the pipe plants thus adversely affected were content to have this occur rather than see-a plant started to supply the surplus demand.

Jan 9, 1924

By E Yurakov, D J. Ashelford, M I. Slate

The push for increasing coal production rates continues to place increasing demands on mine management to safely and effectively control seam gas. Gas drainage strategies applied vary in both effectiveness and form. Methods employed are a function of assessed risk, gas reservoir characteristics, surface and underground access, budgetary constraints and gas utilisation potential. With the aim of establishing and optimising the effectiveness and efficiency of gas drainage systems, Australian coal miners in cooperation with gas management specialists are embracing the use of gas reservoir simulators and gas emission models. This paper discusses the evolution of gas drainage practices in Australian underground coal mines and the role of gas reservoir assessment methods in optimising gas drainage systems and gas production forecasts.

Jan 1, 2005

By L. G. Wilson

In order to comply with time limitations imposed by this symposium, a very narrow but nonetheless interesting segment of the market has been chosen for discussion of the preparation of a tailor-made product to meet a specific need, and in view of the fact that the barite market is one of the oldest and one of the broadest non-metallic mineral markets in the world, it is necessary that we place this in perspective. Of a recent world annual production; (i.e., 1966 figures released last year in MINERALS YEARBOOK), of some four million tons, the United States consumed over 1/2 million tons, of which approximately 950,000 tons were produced domestically and approximately 700,000 tons were imported. Of this total, something approaching 90% was used for drilling-mud weighting, and of the balance, all but about 60,000 tone is consumed in the production of glass, barium chemicals, aggregates, and other minor uses; thus we are really taking a look at a very minute, however important, and very selective, portion of the total barite-market. The real meat of this paper, after eliminating all irrelevant uses of barite, and delineating the area of discussion, resolves itself into the approach to a favorable marketing area and a specific attack on that area. Cost, to the user, has been, patently, a function of distance, as the basic price of barite has varied very little over the years until recently, and freight rates have been the governing factor. Conversely, the seller of barytes must make concession in the plant price to compensate for distance, if he is to successfully compete.

Jan 1, 1969

By D. S. Saxena, Jack K. Tuttle

Lack of understanding of useful applications of explosives on construction work stem primarily from the fact that explosion is commonly associated with destruction. On rock excavation and other construction works a certain quantity of explosive is harnessed to perform useful work at the source e.g. blasts to disintegrate rock. Development in rock blasting techniques, including the use of multiple-row blasting with short delay ignition, have made it impossible to excavate rocks close to or below buildings even in closely built-up areas. To permit the use of explosives on construction projects, in ways that will not damage existing structures, guidelines have been developed from careful measurements of intensity of ground vibrations. Accurate electronic instruments are now available for doing this. PLANNING AND CONTROL Blasting operations must be carefully planned and carried out to avoid discomfort to persons or damage to property. This increase in the use of rock blasting in city areas alone has led to a number of problems due to ground vibrations, air shock waves, and the psychological effect of noise. While the latter seldom if ever causes damage, it does create irritation and discomfort to persons living or working near the blasting sites. A result of this is a steady increase in the number of complaints in respect of damage to houses and other premises. Many such complaints are genuine and damage may undoubtedly be caused when incorrect blasting techniques are used.

Jan 1, 1997

By M. J. Coolbaugh

There is a need for concepts and techniques developed specifically for blasting in areas where the rock is loose or highly fractured. Common practice has been to use techniques developed in hard homogeneous rock and reduce the amount and strength of explosive. However, this rule cannot cope with all of the special characteristics of highly fractured rock and has not adequately taken care of the problems of overbreak, gouging, and wall damage. The main problems encountered when blasting in highly fractured rock are controlling the amount of rock broken, minimizing the damage done to the remaining wall material, and adapting blasting methods to rapidly fluctuating ground conditions. In addition, because it frequently needs timber support right into the blasting area, there is also the problem of how not to shoot out the timber when heavy loading is needed in order to offset a loss of impact caused by deflection of the detonation wave off the numerous rock interfaces, and by the absorption of the wave by resilient clay particles. Another consideration is the fact that less attention needs to be directed toward producing satisfactory fragmentation of the broken rock. Those blasting methods designed for breaking hard rock into manageable segments are, as a rule, not needed in highly fractured rock which will usually break along its own numerous fracture lines.

Jan 8, 1965