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By B. Hornsby

At the Mount Isa mine, Mount Isa, Qld., Australia, sublevel open-stope mining is used for copper ore while both sublevel open-stope and cut-and-fill methods are used for the silver-lead-zinc ores. Production in 1979¬80 was 4 730 000 t (5,200,000 st) copper ore and 2 590 000 t (2,850,000 st) of lead ore. The deepest mine level currently is 960 m below the surface. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size, Shape, and Dip The mine is located in the valley of the Leichhardt River in Lower Proterozoic sediments of the Mount Isa group. The regional strike of the sediments is north¬south and they have a persistent westerly dip of about 1.1 rad (65°). In the mine area, the Mount Isa group comprises a sequence of alternating bands of dolomitic shales and siltstones some 3.2 km (2 miles) in width. It is bounded on the east by greenstones and quartzose sediments of the Eastern Creek volcanics, and on the west by the Mount Isa fault, west of which occur schists and other metamorphic rocks. The ore bodies as currently known at Mount Isa are restricted to the Urquhart shale, a formation of thinly bedded pyritic, dolomitic, and volcanic shales some 1070 m (3500 ft) thick. Towards the top of the Mount Isa group sediments, copper and silver-lead-zinc ore bod¬ies occur as contiguous but discrete entities and are mined and treated separately (see Figs. I and 2). Argentiferous galena, sphalerite, pyrite, and minor associated sulfides occur in distinct concordant bands throughout the Urquhart shales. Wherever these bands are grouped together in sufficient density they constitute silver-lead-zinc ore bodies with widths varying up to 36.6 m (120 ft). Other mineralized bands are common in intervening beds. Individual ore bodies persist for many hundreds of meters concordant with the strike and dip of the enclosing shales. Intersections of these beds with fold axes provide local zones of enrichment but otherwise the mineral content of the ore bodies varies only slightly throughout the extent of the dip and strike. Chalcopyrite is the only important primary copper mineral. It occurs in association with pyrite and pyrrhotite as disseminated flocks and as vein fillings throughout irregularly shaped zones of folded, brecciated, and re¬crystallized Urquhart shale. These zones, which are lo¬cally termed "silica-dolomite" bodies, are broadly transgressive to the shale bedding and confine all significant copper mineralization to the virtual exclusion of silver¬lead-zinc mineralization. In some areas, the downward percolation of acidic water through faults and shears has caused extensive leaching of the coarse-grained carbon¬ates to depths in excess of 610 m (2000 ft), but most of the silica-dolomite remains unleached and the ground is competent. The majority of lead ore being mined is north of the main shaft pillar (R62, U62) area. The major lead¬producing areas for many years have been the Black Star ore bodies (2 and 5 ore bodies) and the Racecourse ore

Jan 1, 1982

By Duane B. Jorgensen

The two calcium sulfate minerals, gypsum and anhydrite, occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO, . 2H20) and anhydrite, the anhydrous form (CaSO,) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the larger part of total calcium sulfate resources. Although it has very minor economic use, it is important to the understanding of gypsum deposits and is referred to frequently in the following discussion. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [ ] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have not yet been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. Most gypsum produced ranges from 80 to 95% pure and beneficiation is normally limited to selective mining or quarrying or upgrading by crushing and screening during mill processing. END USES The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris, the hemihydrate of calcium sulfate (CaSO4 ½ H2O), which when mixed with water will set or harden as the calcium sulfate returns to the stable dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uses of uncalcined gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in other countries with building practices different from those in the United States and Canada, relative usage varies widely. Calcium sulfate deposits are the world's largest sulfur resources; minor quantities of gypsum and anhydrite have been used to produce sulfur or sulfur compounds. This use is accompanied by a unique site-specific set of economics because sulfur is generally available from non-gypsum sources at lower cost.

Jan 1, 1994

By Adrian Brown

Groundwater inflow and impacts have become major aspects in the permitting and operation of many gold mines. First, the hydrothermal or placer genesis of many of the orebodies being investigated or produced today almost guarantees that mines will be "wet", involving groundwater control as part of operations. Second, the style of ore deposition a1 so often involves a1teration of the host rock, resulting in relatively weak, low permeabi1ity materials that require extensive groundwater pressure control for stable mining. Third, the location of many mines in arid areas guarantees that impacts on water resources will be matters of key focus during permitting and operation. However, groundwater control and protection is a technically difficult area and often involves managerial decisions and activities that do not fit comfortably into traditional mining. In an attempt to overcome some of these difficulties, this paper provides a guide to mine managers and hydrologists as to appropriate strategies for designing, setting up, operating, and evaluating groundwater programs at gold mines that get the job done and are cost effective.

Jan 1, 1988

By G. J. J. Aleva, A. H. Hilversum

The northern spur of the Bakhuis Mountains contains bauxite deposits on a dissected planation level, a region formerly indicated as the Adampada-Kabalebo area. Iron-rich laterites are ubiquitous on all more or less flat and horizontal to moderately sloping interfluves and planation levels. The known aluminous laterites and bauxites are restricted to those laterites that have relatively leucocratic and silica-poor parent rocks. The whole area is underlain by high-metamorphic Precambrian. In the northern half of the Guiana Shield at least four Cainozoic planation levels can be distinguished. The bauxite and aluminous laterite deposits are related to the oldest, Early Tertiary level. These deposits, occupying the highest positions in the present day landscape, show the destructive influence of post-laterite weathering, erosion and denud- ation; they are erosion remnants and as such are of irregular thickness, grade and shape. Consequently, exact mineable tonnages can only be determined after intensive and detailed sampling and evaluation, taking into account the latest technical and economic parameters. The bauxite potential of the region is negatively influ- enced by the complicated uplift history of the Bakhuis horst, and positively by the presence of suitable parent rock and possibly more than one phase of bauxitization.

Jan 1, 1984

By Jorgen Elbrond

Shovels, trucks and repair bays for the trucks each play their role in the capacity of an open pit operation. It is therefore convenient to have a procedure for the capacity calculation which takes all 3 factors into consideration in a comprehensive manner. This can be done by means of a cycle model, earlier developed for the shovel-dumper circuits, when the repair facility with its number of repair bays is added as a superimposed service system, which the trucks visit at certain specified intervals. The calculation model transforms the mechanical availability of the trucks into their operational availability. The system's capacity in truckloads per shift and the trucks' operational availability of certain combinations of shovels, trucks and repair bays are shown.

Jan 1, 1981

By Gordon I. McPhail, John D. Nelson

Tailings management represents a major portion of the cost associated with extraction of gold. For each gram of gold extracted, 150 to 200 kg of waste material is produced. Because of environmental concerns and unwillingness of society to accept environmental damage caused by poor waste management practices it has become essential to follow responsible and safe practices in tailings management. This paper presents general aspects of tailings management and discusses different techniques utilized. Characteristics of tailings and the effects that these have on stability and environmental aspects are discussed. The paper also discusses the effect of mine back-filling practices on the surface disposal of the remaining tailings fraction.

Jan 1, 1987

By L. Adler

INTRODUCTION The purpose of this paper is to describe in engineering terms the singular and basic operational kinematics of all excavating and bulk handling equipment. The safe and efficient use of equipment will be fostered by enabling the engineer to conceptually duplicate the operators' "tasks" in directing and controlling it. A simple graphical and notational scheme will be introduced to define the essential gross repetitive motions. The significance of this effort includes filling a vital analytical gap at the work face, and in establishing direct communications between the engineer and equipment operator. Since all types and sizes of earth- moving equipment are covered, a major concern has been to integrate equipment specialties into d single encompassing discipline. Equipment types are closely related to the working conditions, and their selection and evaluation are also considered. The extension to human factors analysis is natural and predictable. Since human [actors are involved, the operational analysis can also be considered a catch-all for many subtle vagaries. BACKGROUND Symbolic modelling linked to a notational system will be developed and intensively used. This constitutes the "language of science," providing a shorthand method which gives immediate recognition, is fluent, explicit, reinforcing, unequivocal and provides limitless associations. Many examples of symbolic modelling exist in chemistry, physics, the military, engineering sciences and it is a major tool in mapping. Its use is so ubiquitous that it often goes unnoticed. On the other hand it must be realized that something is lost in simplifying and idealizing what is an extraordinarily complex occurrence. The components describing the basic operational kinematics of equipment include: (1) the vehicular motions as a rigid body and (2) the job-end motions focussing on excavating (Adler, 1985). These provide all of the components in the load-haul-dump sequence (L-H-D) , and will yield three dimensional expressions. Complex patterns can also be assembled from these simple elements. An existing equipment designation employed in earthmoving will be integrated into this approach (Carson, 1961). Along with the basic motions, corresponding working conditions will be noted.

Jan 1, 1986

By Bonn J. Macy, David A. Gulley, William A. Vogely

INTRODUCTION Some of the most famous and graphic environmental incidents have arisen from mineral extraction, including oil spills, the Reserve Mining asbestos tailings case, Kaiparowitts surface mining and coal combustion, and other environmental causes celebre. The remote location of much of the mining industry to some extent reduces the human health hazards from pollution, but often times the pristine locale in which mining is conducted provides a sharp contrast to the impacting industry. This prompts questions as to what the research literature says about the true costs and benefits of environmental compliance. We survey the state of this knowledge. Where possible, we discuss studies focused on mining and related industries, such as primary metals production. In many cases, how- ever, the studies pertain to the economy as a whole. For present purposes, the mining industry is defined as companies engaged in the production and refinement of minerals, including metals, fuels, and nonmetallics (e.g., phosphate, sand and gravel). There are several stages in mining, with environmental effects occuring at every stage. The exploration stage comprises the period from initial prospecting to the point where the deposit has been located and delineated in sufficient detail to permit development decisions to be made. Geophysical and geochemical surveys, diamond drilling programs, and exploratory stripping and excavation are activities that may be employed during this stage. Some forms of prospecting are relatively benign, al- though even airborne surveys and motor vehicles generate noise pollution. Roads and the passage of vehicles and equipment affect land surfaces and vegetation, and attract heavier backcountry use. Clearings, stream crossings, and borrow pits can lead to increased erosion and sedimentation of streams. Geological survey grids disrupt vegetation and appearance. Moreover, prospecting can involve the excavation and stripping of overburden, resulting in soil and vegetation disruption as well as in- creased sedimentation of streams and lakes. The effects of exploration are often temporary, and frequently less severe than for other activities. Nevertheless, exploration-related impacts vary with the intensity and type of exploration effort, and can be significant. During the development stage of mining, shafts are sunk, pits excavated, buildings erected, and transportation facilities established. Dust, noise, and other socioeconomic and environmental impacts are generated by the relatively large and sudden influx of people, equipment, and activity. Surface disturbance and solid waste are generated by development, and liquid wastes form when mines are dewatered. The extraction phase is associated with a variety of environmental impacts. These impacts may differ for surface and underground mines. In surface mining, surface disturbance is obviously a major consequence. Piles of overburden and waste accumulation mar land surfaces. Wind and water erosion tend to spread the dis-

Jan 1, 1985

By A. C. Lyons

Foreword Sir William Halcrow and Partners are responsible for the design of the Ahmed Hamdi Tunnel as Sub-contractor to the Contractor, Osmac, a joint venture formed by the Arab Contractors, Osman Ahmed Osman and Company of Cairo, and Tarmac International of London. Throughout the paper the term "Client" refers to the Employer, the Ministry of Housing and Reconstruction, which latterly became the Ministry of Development and New Communities of the Arab Republic of Egypt. At the time of writing of this paper only a few hundred metres of the tunnel have been driven, but the design is substantially complete. Introduction The Ahmed Hamdi Tunnel, which is at present under construction, will be a two-lane tunnel crossing beneath the Suez Canal approximately 15 km north of the town of Suez at El Shallufa. It will become the first permanent connection across the Canal since 1967 and is visualised by the Egyptian Government as an early step in the development of the Sinai Desert along the eastern bank. The tunnel will carry pipelines for treated water and electric power cables to assist in this development. The tunnel, which will be 1640 m in length, is being driven through hard clay and mudstone using a tunnel shield fitted with hydraulic excavators. The primary lining is being constructed with precast, bolted reinforced concrete segments with an internal diameter of 10.4 m. The road deck structure and the walls of the air supply ducts beneath it are formed with precast, reinforced concrete units erected immediately behind the shield.

Jan 1, 1979

By B. Markovic

Performance of mineral filler particles in ceramic applications can be enhanced markedly by adsorbing polymers of optimum molecular structure and dosage. In a recent work by Chen and Somasundaran (1997), a novel scheme of controlled polymer adsorption was used to produce nanocomposites of unique core-shell designs. Towards this purpose, adsorption and desorption behavior of selected polyacrylic acids (PAA) on three minerals; alumina, titania, and silicon carbide, was examined as a function of relevant parameters. Adsorption of P AA was found to depend on polymer molecular weight, pH, as well as solids loading. Specifically, the adsorption density was found to increase with increase in polymer molecular weight for non-porous alumina while it was found to decrease in the case of porous alumina. This is attributed to the inaccessibility of the pores to the larger polymers. An unexpected finding was the change in the adsorption density of PAA with solids loadings. PAA adsorbs on silicon carbide only at low pH values when the particles have very low surface charge suggesting that the adsorption in this case is controlled by electrostatic forces. Using polyacrylic acid as bridging agent between the alumina fillers (core) and nanosize alumina or titania particles (shells), controlled layer by layer deposition of nanoparticle on the core particle surface could be obtained.

Jan 1, 1997

By William F. Hahn

It is a pleasure to speak to this group about special crusher installations which are in the bauxite and phosphate rock processing industries. The installations to be discussed demonstrate the variety of conditions, materials, and results desired which must be evaluated before a selection is made from the specialized crusher technology available today. Those of you who are closely involved with phosphate rock and phosphate products processing will find some of this information a bit interesting and perhaps alien to your own descriptions or every day references. It is given from a "crusher" manufacturer's viewpoint and therefore is infused With our flair and language. General features of six (6) different crushers will be shown in cross-section With slides and will be discussed in the same order.

Jan 1, 1978

By H. Sis, S. Chander

The pressure filtration behaviors of dispersed and flocculated alumnae slurries at high percent solids were investigated with the objective of determining the effect of surfactant type and concentration on slurry properties. A high-purity alumina powder was used as a model solid. Dispersion of the alumina was controlled by pH and by surfactants that are known to act as electric and steric stabilizers. The effects of both ionic and nonionic sutfactants were investigated. Surface charge measurements of the slurries were carried out by an electrokinetic sonic amplitude (ESA) method to better understand the mechanisms. The effect of surfactant type and concentration on the kinetics of pressure filtration and cake properties are discussed.

Jan 1, 2000

By Pedro E. Rengifo

Splicing methods have undergone considerable developments over the last 2Oyears. Continuous conveyor belt service is dependent entirely on the strength and life of the splice to hold the two ends together. Ultimately, belting performance is dependent on the quality, efficiency, and technique of the splicer. As customers demand better belting performance and running tensions increase, the need for splices that perform as efficiently as the belting has increased also. Higher dynamic belt constructions have also dictated the need for "new"sp1icing techniques. Regardless of the belt type used or spliced, one item that is most necessary with all belt types is the quality of the workmanship and standardized splicing methods that employ all of the necessary elements required to ensure reliable field service. This paper will explore the use of Goodyear-issued internal standards for field splicing following the constraints of quality and efficiency for fabric and steel cord reinforced belting. Also included are the 10 most common mistakes made by splicers, Goodyear-issued Field Quality Assurance Standards, and check lists for end users to adhere to the manufacturers' requirements for splicing including materials and specifications for conveyor belt splicing and repairs.

Jan 1, 2004

By M. B. Thorpe

Land use and access to land are limiting factors in economic development in the Western region of Ghana. Mining uses land during operations and then rehabilitates the land as part of ongoing operations and closure. Golden Star Resources Limited (GSR) aims to contribute to the sustainability of the local economy during its operations and then post-closure. Following a series of alternative livelihood initiatives, GSR reviewed the success of these programs and decided to focus on an oil palm project that uses out-growers to reach the local economy. The project started using small holdings that were individually managed. However, the ongoing effects were limited. Following a review of the options, the Golden Star Oil Palm Project was started using land committed to the pro-gram by the Bogoso Mine. The initial program covered 275 ha with over 40,000 trees with 300 people involved in the development. The Traditional Authorities have committed additional lands to the project to a planned total area of 18,000 ha.

Jan 1, 2007

By E. I. Jurgens, K. E. Hanney, D. C. Comrie, R. H. Fletcher

Introduction The reclamation of mine/mill tailings areas is undertaken for a variety of objectives including safety, appearance, economical use of lands and forests and long term storage of a future resource. The establishing of criteria for these objectives at any site is a shared task of the government and mining company. Our attention in this paper is directed to uranium mine/ mill tailings as they are handled in the Canadian industry and in the unique Canadian climate. We focus our attention on the state of the art. Uranium is a ubiquitous mineral forming an average of 4 g per tonne of the Earth's crust. Ores are mined at about 500 g per tonne so that the residual content of uranium in tailings is comparable to average background levels. However, as in most mine/mill operations, the ore contains other minerals that become readily mobile after milling operations. Thus the main objective of tailings impoundment is the stability both physically and chemically of the mobile materials. Since the requirements for the operation and construction of tailings areas in Canada have changed considerably over the past decade, there exists a great many mine/mill tailings areas which while considered adequate in their day, would not meet modern criteria. However, most of these installations pose no concern or hazard to the public. The proximity of mine/mill development to inhabited land areas has necessitated more stringent modes of tailings operations and provisions for tailings site reclamation. The more important of these have been: 1) the prevention of dyke failure, with large liquid-solid outflows onto adjoining lands, and 2) the prevention of seepage from the tails of pollutants such as chlorides, sulphides, heavy metals and radionuclides. Uranium mill tailings are discharged as a slurry from the concentrator after the removal of generally only about 1000 g, or less, per tonne of uranium from the as-mined ore. As a consequence, a great volume of low level activity waste is generated. The amount of tailings is expected to grow in quantity in the future even faster than the increase in yellowcake production, as the demand for energy

Jan 1, 1980

By Numan Elmas

Barite deposits located in Dinek and surrounding region have important economic features with their large reserve capacity for Turkey. The objective of this study is to elucidate geological and depositional characteristics in terms of. site investigation and chemical analysis. In order to do this, geological area of about 300 km2 was examined and detailed geological map was constructed. It was observed that Barite mineralization in these deposits was occurred in carbonate and pelitic rocks of Lower Cambrian-Lower Ordovician. Deposits were exposed to advanced diagenesis regional metamorphism and tectonics that rotated and deformed the barites; therefore, barites shows secondary veins, brecciate and fracturing structure. Even though, a few light isotope values of barites may suggest hydrothermal and exhalative sedimentary characteristics or possible mixing with magmatic fluids, generally heavy isotope values indicate that the sulfate ions were supplied from coeval seawater and, many of sedimentary features and petrological, geochemical characters support dominantly sedimentary origin.

Jan 1, 2005

By Jose M. Milian, Raphael F. Matson

An intensive study was started in 1968 to determine the most economical process for winning nickel and cobalt from an extensive de- posit of complex, low grade nickel-cobalt ore (1.6% Ni, 0.10% CO) designated "the Greenvale ore." In 1974 the commercial plant at Yabulu, in Queensland, Australia, began processing the ore. In the interim, a great deal of laboratory and pilot-plant effort was applied to develop technical, process and commercial design data to demonstrate to potential financial backers and customers that a full-scale plant was feasible. The laboratory test work, pilot plant facilities and pro- gram are briefly reviewed in this paper.

Jan 1, 1979

It doesn't take any special acumen to note that US engineering and construction firms are busier than ever with mining projects in this mineral conscious world. This special issue of Mining Engineering takes a look at E&C companies-their expanding role, their special capabilities, and their challenges and problems. ME sent a questionnaire to a representative sample of E&C firms. Information was sought about officers, ownership, and amount of business. ME also asked about types of projects and commodities dealt in as well as market distribution and forms of payment. The accomnanying charts show how the 17 responding E&C firms answered these and other questions. Other ME survey questions, and a review of company literature, yielded information about financing techniques and special challenges for E&C firms. Insights were gained concerning government impacts, customer-generated problems, and promising areas for development-including synfuels-in the minerals industry. These areas are discussed later in this article. Accompanying articles in the special issue discuss the E&C company's role in mining projects, research and development in E&C firms, one approach to contract work used by an E&C firm, and an E&C project case study.

Jan 10, 1980

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

The STG integrated method of grouting can be divided into the several phases as outlined in preceding chapters. For convenience in describing technical procedures, they can be grouped as: 1. Investigations in non-geotechnical, exploration bore¬holes. 2. Drilling the holes necessary for geotechnical investiga¬tions and for grouting. 3. Conducting appropriate hydrogeologic tests in those holes and consequent calculations. 4. The preparation of a clay mortar. 5. The preparation of a clay-cement grout with additives. 6. The injection of the grout. 7. Checking the quality of the grout curtain. Items 2, 4, 5 and 6 are discussed below. These activities contain the procedural aspects of grouting. 7.1 DRILLING GROUT HOLES Grout holes belong to a very select class of drillholes. The necessary drilling equipment must enable the operator to drill the holes in inclined, twisting directions. In addi¬tion, the equipment must permit drilling under structurally and hydrogeologically complex conditions. The equipment must permit the operator to conduct specific testing activi¬ties in the drillholes. These activities include hydrodynamic analyses, flowmetric analysis, and the installation and re¬moval of deflectors, packers, grouting plugs, casings, lin¬ers, pumping facilities and other work. As explained in Chapters 5 and 6, the grouting of sat¬urated rock is conducted both through holes drilled from the surface and through holes drilled from the face of a shaft, drift, or tunnel. The drilling of grout holes from the surface can be carried out by an aggregate of equipment that can be the same equipment used for drilling exploration boreholes. Depending on the projected depth of the holes, the STG ZIF- 1200MR and ZIF-650 drilling rigs (or modifications of them) are used. The SKB-4, SKB-5 and SKB-7 high-output drilling rigs (workover rigs) have been used in recent years. The STG BMP-24 drilling rigs are used for carrying out the descent-lifting operations for drilling holes from the sur¬face. In a number of cases, the UKB-500C, URB-3AM and URB-2A power-fed drilling equipment is used for drilling holes from the surface. It should be noted that the drilling of grout holes usually requires an electric drive assembly. Drilling with diesel drive assemblies would be used only to preclude the possi¬bility of losing electric power during drilling operations. Turbine drilling would be used only for appropriate techni¬cal-economic reasons. The selection of the grout hole design is determined by the hydrogeological and structural geological conditions at the site as interpreted in Chapters 2 and 3. The design of grout holes must be as simple as possible in order to min¬imize costs. Hole design guidelines can be adopted as a basis for this purpose, unless site-specific conditions require otherwise. The mouth of the drillhole must be outfitted with a guide-pipe having a length of at least 2 m and an outside diameter from 219 to 234 mm. The upper part of the hole must be attached by a jig consisting of borehole casing that has a diameter ranging from 108 to 146 mm. The length of the jig h is determined by the equation [ ] where k = 1.1 to 1.2 is the load factor; P,, is the injection pressure of the grout into the mouth of the drillhole; D is the external diameter of the jig pipe; m = 0.6 to 0.7 is the work condition factor; T[ ].1 MPa is the bonding value of the rock cemented to the jig. The grout hole is drilled from the jig shoe to the de¬signed depth using a rock-crushing bit with a diameter of 93 mm or more. However in complex hydrogeological condi¬tions when the shaft intersects unstable rock, other hole designs can be used. The diameter of grout holes must permit an aggregate of investigations to be conducted in them using down-hole borehole geophysical and flowmetric logging instruments. It is necessary to cement the casing strings reliably in the grout holes, thereby permitting the injection of the grout under high pressure through the pres¬sure tight mouth of the borehole. Technological details for drilling grout holes such as the rotational rate of the drill bit, the axial load on the rock¬crushing bit, and the drilling fluid flow rate are optimized for the specific rock-hydrogeological conditions largely by experience. The hole diameter and type of rock crushing bit are important variables in these details of drilling. It is advisable to drill holes using water as the drilling fluid. However in those cases where the hole walls are unstable or under very high ground water pressure, the use of a well¬ engineered drilling mud should not be precluded. Unfortu¬nately, drilling mud can influence test results. When steeply dipping fractures with inclination angles of more than 60 to 70° are encountered, it is necessary to drill guided, inclined grout holes. This procedure permits the maximum number of fractures in each hole to be stu-

Jan 1, 1993

By Heinz Kettling

Labor costs, which have rapidly increased in the industrial countries for several years, have forced the mining industry to develop new methods and cost saving systems. Also, because mining is basic to meeting the increasing requirements for raw materials, the mining industry is guaranteed a key position in cost cutting efforts. Although this report aims to describe major recent developments in the Federal Republic of Germany, it is restricted to a limited number of them in view of the wide variety of current innovations. The most important mining activities in West Germany are concentrated in the coal mines on the Rhine, Ruhr and Saar, in the lignite open-cast mines west of Cologne and in the potash and salt mining region in Lower Saxony and Hesse. This report will only discuss developments in the underground coal mines and the potash and salt mines, and focuses on projects of Salzgitter Maschinen and Anlagen AG (SMAG). HYDRAULIC DRILLS Drilling strata of varying strength One special difficulty faced in European coal mines is the varying of compressive strength of strata that occurs even over a few meters. The strata associated with the coal measures ranges from hard and tough sandstone or conglomerate to very soft carboniferous shale. It is often difficult to use continuous miners or roadheaders so that drifting by blasting still predominates. But the varying compressive strengths of the strata makes it difficult to choose the best method to drill the rock. For example, it is best to penetrate hard sandstone or conglomerate with heavy percussion drills. The soft carboniferous shale on the other hand, should be penetrated by high speed rotary drilling to obtain optimum performance.

Jan 1, 1979