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By N. I. Fisher, J. Shepherd

Abstract-Statistical studies have been carried out on structural geological data collected across a large zone of roof failure 600 m (1968 ft) wide and at least 800 m (2642 ft) long in the Greta coal seam at Aberdare East Colliery. Two swarms of hundreds 2 of minor, normal faults with throws commonly between 3 and 300 mm in the room and pillar workings are broadly coincident with roof failure. The faults have been classified into dip slip and oblique and strike slip types. Roof conditions have been classified into good; troublesome with subclasses scaly, heavy, gutter falls and wide, flat-roofed falls; and severely failed with subclasses very heavy roof, gutter falls and dome falls. Troublesome conditions are defined as those in which the height of the fall is less than or equal to 0.3 m, and severely failed conditions as those in which the fall height is greater than 0.3 m. Comparison of faults, roof conditions and mining rate on a shift basis indicates that faults and roof failure are much more important than machine breakdowns in reducing mining rate. The effect of faults on roof conditions has been quantified using a concept called the "zone of influence, " a rectangular area around a fault in which the fault has potentially deleterious effects. The spatial comparison of fault "zones of influence" with areas of roof failure using Spearman's rank correlation coefficient shows that, while normal dip slip faults do not appear to be associated with roof failure, oblique slip and strike slip faults appear to be associated with roof classed as severely failed. The "zone of influence" of an oblique slip fault may extend up to 3 m on each side of it in the headings and up to 1.14 m in the cut-throughs. The fault "zone of influence" has geomechanical implications for the design of mine openings and possibly represents the maximum length of a cantilevered roof beam likely to fail during mining, owing to a fault. Roof conditions could possibly be predicted in blocks of virgin coal if the type of fault could be identified in oriented drill cores.

Jan 9, 1978

By Phil Hulse

The Atlanta mine is located in east-central Nevada, approximately 360 km (225 miles) from Las Vegas. It lies in Lincoln County, 116 km (72 miles) south of Ely and 80 km (50 miles) northeast of Pioche. The property is currently operated by the Standard Slag Co. under a joint venture agreement with Bobcat Properties Inc, of Fort Lauderdale, Fla. Operations began in May 1975, and the mill is currently processing 109 000 to 122 500 t/y (120,000 to 135,000 stpy) of gold- and silver-bearing ore. Open-pit mining takes place in a breccia zone that occurs between Ordovician limestones and dolomites on the footwall and Tertiary rhyolites on the hanging wall. The quartz breccia ore is among the most abrasive in the world-shovel teeth must be replaced every week, 19-mm-thick (3/4-in.) steel chutes last about a month.

Jan 9, 1978

By John D. Wiebmer

Kansas, with its thin seams and tough overburden, may not be anyone's first choice for a coal mining operation. But there are operators making it pay through careful attention to mining techniques and aggressive marketing in the local region. One of the few Kansas coal operators is Bill Patch, who has been in the business for 28 years. Beginning with a single dragline operation near his home in Welch, Okla., Bill's Coal Co. weathered some lean times during the "soft" coal market of the 1950's and 1960's. But his tenacity paid off when new markets began opening up, and the company has grown by leaps and bounds in recent years. In 1975, the Fort Scott mine opened in Bourbon County, Kansas; in 1976, the Porter mine began production in Wagoner County, Okla.; in 1977, the Fulton mine opened near Fulton, Kansas. In addition, the original Welch mine in Oklahoma is still a producer, and this year the company will open a new mine at Chetopa, Kansas.

Jan 9, 1978

One of the first all-hydraulic crawler drills in service at a US open-pit mine has significantly exceeded the penetration rates of comparable pneumatic crawler rigs, according to Atlas Copco Inc. Overall production with the hydraulic unit has been double that of pneumatic crawlers in use. The installation is at the Foote Mineral Co. surface mine at Kings Mountain, N.C., where the company is engaged in mining spodumene, a combination of lithium, aluminum, and silicates. The ore is found in pegmatite dikes, a tough and abrasive host rock with compressive strength of tip to 5800 kPa (40,000 psi).

Jan 9, 1978

By J. F. Sepulveda, J. D. Miller

Tar sand deposits in the state of Utah contain more than 25 billion bbl of in-place bitumen. Although 30 times smaller than the well-known Athabasca tar sands, Utah tar sands do represent a significant domestic energy resource comparable to the national crude oil reserves (31.3 billion bbl). Based upon a detailed analysis of the physical and chemical properties of both the bitumen and the sand, a hot-water separation process for Utah tar sands is currently being developed in our laboratories at the University of Utah. This process involves intense agitation of the tar sand in a hot caustic solution and subsequent separation of the bitumen by a modified froth flotation technique. Experimental results with an Asphalt Ridge, Utah, tar sand sample indicated that percent solids and caustic concentration were the two most important variables controlling the performance of the digestion stage. These variables were identified by means of an experimental factorial design, in which coefficients of separation greater than 0.90 were realized. Although preliminary in nature, the experimental evidence gathered in this investigation seems to indicate that a hot-water separation process for Utah tar sands would allow for the efficient utilization of this important energy resource.

Jan 9, 1978

By J. Wright, R. J. Tyler

Abstract-Changes in the pore structure of hematite pellets during reduction to iron were investigated under a variety of experimental conditions. Pore structures were determined by a mercury penetration technique. The reduction temperature was found to be the major influence on structure, the pore system being bimodal below 750°C and unimodal above 900°C. Pore sizes ranging from 0.04 to 20 [um] were observed in completely metallized pellets produced over the temperature range 650-1050°C. Gas composition and reduction rates also influenced the pore structure of the metallized pellets, although to a lesser extent than the reduction temperature. An apparent activation energy of 24 kcal/mole was derived for the pore formation ptocess.

Jan 8, 1978

By R. W. Nash, A. E. Schwaneke, V. R. Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western prophyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized - 2.5 + 1. 3-cm (- 1 + 1/2- in.) ores from the Kingston (0.9% Cu) and Centennial (1.6% Cu) mines of Upper Michigan. Concentrates of 4.0% and 7.5% Cu, respectively, were obtained at recoveries of 85 and 80% of

Jan 8, 1978

By Robert M. Dreyer

Although lateritic ore deposits are relatively flat-lying, surficial ore bodies, the evaluation of lateritic bauxite and nickel deposits is among the most difficult problems confronting an economic geologist. Laterite is a soil formed under tropical conditions resulting in the concentration, within the soil zone, of certain trivalent metals-principally iron and aluminum, but also, locally, nickel and manganese. The soil zone is divided into two parts: (a) the true soil or lateritic zone and (b) the zone of partially altered bed rock or saprolite. Whereas bauxite generally is confined to the lateritic zone, some nickel deposits occur in both the laterite and saprolite zones. The evaluation of bauxite and lateritic nickel deposits thus has both similarities and differences. These ores have been formed by supergene, soil-forming solutions moving downward through zones of widely varying permeability within the weathering rock. Because the permeability varies widely, both vertically and laterally, the extent of weathering may vary greatly within short distances. Because the weathering process varies widely, the degree of metal concentration may also vary widely. It is not at all uncommon for a laterite to change, within a few centimeters, from a virtually valueless rock to a high grade ore. Moreover, the depth of weathering, and hence the depth and form of the ore profile, vary greatly. Obviously, for this type of deposit, a few grab samples or a few drill holes are virtually worthless. The evaluation of such a deposit requires a sophisticated statistical study based on thousands of carefully selected samples. As a rule of thumb, the cost of evaluating a large bauxite or lateritic nickel deposit will be about one cent per ton of ore in the ground. Thus, the cost of evaluating a several hundred million ton deposit may be considerable.

Jan 8, 1978

By John D. Weibmer

A remarkably simple construction system that derives its internal stability from metal straps buried in backfill is finding diverse mine applications, ranging from rock crusher headwalls to massive slot coal storage facilities. Reinforced Earth (Re/Earth), the system trade name of Reinforced Earth Co., is proving itself 20-50% less expensive than alternative earth embankment structures, and in the case of cast-in-place concrete walls, six to seven times faster to erect. While the majority of applications are in the realm of civil engineering-projects such as retaining walls, bridge abutments, slide buttresses, and containment dikes-a growing proportion is mine related. Of the estimated 120 Reinforced Earth projects that will be completed this year, company president David P. McKittrick expects mining to account for about 20% of the business volume.

Jan 8, 1978

In the maintenance of rubber-tired mining equipment, tires may well represent the single greatest problem. Using a 50-ton truck as an example, engine upkeep averages about 8% of the machine's total yearly operating cost, while tires average a whopping 20%. In fact, depending upon such factors as job layout, conditions, and whether it is maintenance or production people who run the job, tire costs can climb to as high as 50% of the truck's total operating expense. Similar costs apply to other earthmoving equipment such as tractor-scrapers and front end loaders. While operators must resign themselves to "normal" tire life and wear, there are many corrective steps that can be taken to fight the "abnormal."

Jan 8, 1978

By H. R. Green, D. M. Lamb, A. D. Taylor

The design of slurry launders has usually been based on strictly empirical concepts. An examination of the most common procedures reveals that they do not account for many of the variables that are recognized as significant for slurry transport. These may include flow rate, volume concentration of solids, solids specific gravity, solids size distribution, particle shape, launder geometry, and roughness of the wetted surface. It was decided to develop a design procedure, which would accomplish two things:

Jan 8, 1978

By Charles S. Robinson

Abstract-The Henderson ore body is east of the Continental Divide in the Front Range of the Colorado Rocky Mountains, about 80 km (50 miles) west of Denver. The ore body is being developed for mining by workings that extend more than 1100 m (3500 ft) below the topographic surface. During construction of the mine workings, ground water in fractures in crystalline rocks has been encountered. From 1969 to 1973, Charles S. Robinson B Associates Inc., in cooperation with the engineering and geologic staffs of the Climax Molybdenum Company, a division of Amax Inc., studied the ground water geology of the Henderson mine development area. Detailed geologic records of the Henderson mine were available as a result of the exploration, evaluation and development of the mine. Records of the flow, chemical composition and temperature of the ground water at and near the surface, from the entire mine, from portions of the mine, and from exploration holes drilled in the mine, were kept as the mine was developed. Where possible, ground water pressures in drill holes and changes in pressure with time, were recorded. The geologic, hydrologic and chemical data were correlated. The following conclusions were drawn from the correlations: The ground water in the Henderson mine occurs in fractures in Precambrian igneous and metasedimentay rocks and in a series of Tertiary intrusive rocks. Two zones of ground water were recognized; an active zone, in which the fracture systems are recharged and discharged annually into the surface water system, and a passive zone, in which the fractures were filled with water in the geologic past Discharge from the passive zone is through mine workings that intersect the fracture systems. Discharge from a fracture or fracture system is initially high but decreases with time. The rate of decrease inflow (or pressure) is exponential. By measuring the change inflow with time, it is possible to calculate the amount of flow at some given period of time in the future. Based on changes in rate of flow and pressure, and the geology, and assuming rates of mining of the ore, it will be possible to predict the volumes of water that will have to be handled during the life of the mine and the area around the mine that will be drained by the mining operation.

Jan 8, 1978

By G. Kinder, R. Gilges, W. Stoker, R. Davey

The Bingham Canyon Mine, located 48 km (30 mi) southwest of Salt Lake City, Utah, is operated by Kennecott Copper Corporation's Utah Copper Division. This operation is the world's largest open-pit copper mine and produces 96 000 tons (106,000 st) ore and 327 000 tons (360,000 st) waste each day. This material is loaded by large electric shovels and transported by both truck and rail haulage. To meet the requirements of the Clean Air Act of 1970 (as amended), new facilities for the control of smelter emissions were required and are now nearing the final stages of construction. The facility will be capable of treating all the output from the mine, some 2,530 tons (2,789 st) per day of combined concentrate and precipitate. Costing $280 million and necessitating the replacement of reverberatory furnaces with continuous smelting vessels, the plant, with its massive and complex gas handling and acid-making facility, is required to remain on-stream with the minimum of pollution control equipment outages to conform with Federal Regulation 52.2325.

Jan 8, 1978

By Ben B. Sweet

The ongoing controversy over mining and agricultural use of ground water in Arizona underscores the importance of this commodity to both industries. Although the principles presented in this article are fundamental, a method of systematic data collection and interpretation is provided for evaluating a water well by a set of uniform standards common to all areas where ground water is a primary source of supply.

Jan 8, 1978

Percussion drilling with tungsten carbide insert button bits ranks among the most significant advances in both underground and surface drilling in medium and hard rock formations. Getting top performance and life from these upfront components is not particularly difficult if one pays attention to the basics in operation and maintenance. For some reason, a few of the essential operating and maintenance steps for getting the most from these tools seem to have gotten turned around; instead of operating at the near optimum levels, some miners, in following myths or misunderstandings about them, are shortchanging their optimal utilization. Let's examine the two most harmful ones.

Jan 8, 1978

By Betty J. Laswell, Gerald W. Laswell

Rotary drilling in modern open-pit mining is usually considered the lead phase which not only establishes the production rates but frequently limits them. From this viewpoint alone, the drilling phase must be maximized. The drill phase is the step that permits all the other operational phases to function within their design limits. This means that, in most cases, the drill is literally run to destruction to ensure that the shovel will be able to smoothly and consistently load a manageably size muck, the haul trucks can carry a balanced load without having a boulder dropped through the bed, and the crusher can devour constant rock size.

Jan 8, 1978

In the Philippines, where distances are spoken of in terms off fight time, the Sipalay copper mines are two flight hours southeast of Manila on the island of Negros. After landing at the airport in Bacolod, it is then 170 km (106 milers) by surface transportation to Marinduque Mining and Industrial Corp.'s expanding copper operation. While copper deposits were discovered in the area in 1936-and one mine, the Binulig, began operations soon after-it wasn't until 1956 that stripping at Sipalay and construction of a 4000-t/d (4400-stpd) mill began. The mill went into operation in May 1957, and the first shipment of copper concentrate was made three months later.

Jan 8, 1978

At Asarco's Mission mill. located near Sahuarita, Ariz., the 20 500-t/d (22,500-stpd) throughput of highly abrasive and corrosive copper ore can play havoc on equipment wear parts. To minimize frequent replacement work and extend life on key components, Asarco engineers have over the past five years utilized liners made of "Towniprene" in the secondary grinding and flotation area of the plant. Results to date have indicated that these liners last between three and five times longer than those made of metal or ordinary rubber.

Jan 8, 1978

By John A. Von Essen

To some, the paddle mixer may seem old as antiquity. Yet, as industrial mixing requirements become increasingly sophisticated in the late 20th century, it is proving more useful and versatile than ever. From water treatment applications to high-pressure reactors, the new and specialized demands in mixing have been met by a continuous evolution and adaptation of this basic workhorse design.

Jan 7, 1978

By Peter Joralemon

Peter Joralemon's contention that Nevada contains one of the world's major gold belts is the result of 30 years' active involvement with the state's regional geology. He first suggested the possibility of an arsenical gold belt-tenuously based on two replacement deposits 480 km (300 miles) apart-in his 1949 doctoral thesis of the Getchell mine. In the years that followed, some 18 or 20 arsenical gold ore bodies have been discovered along the lineament Joralemon postulated. In this article, he uses the evidence that he's collected over the last three decades to refine his 1949 thesis. Joralemon's conclusion: A mineral belt containing a billion dollars worth of gold extends the length of Nevada, and a number of ore bodies are yet to be discovered.

Jan 7, 1978