Mining Engineering Lecture Notes PDF

MINING METHODS, MINE DESIGN AND UNIT OPERATIONS UNDERGROUND MINING Prof. S. Durucan Department of Earth Science and Engineering Royal School of Mines...

MINING METHODS, MINE DESIGN AND UNIT OPERATIONS UNDERGROUND MINING Prof. S. Durucan Department of Earth Science and Engineering Royal School of Mines Imperial College London 1. INTRODUCTION A producing underground mine requires a carefully planned network of shafts, drifts and raises. The preparation of this network is known as development. In brief, four different basic kinds of rock excavation can be recognised in normal development: shafts, drifts, raises and inclines, Figure 1a and Figure 1b. The main objective of a shaft is to provide access to or a connection with underground. This access may be used for hoisting rock and ore, personnel and material transport, ventilation, etc. The shape may be rectangular, circular or elliptical, however, circular shafts are the most popular as they are more stable and easy to line. Most modern shafts are circular. The horizontal drifts in a mine are used for various purposes: development tunnelling, exploration, haulage etc. A raise in a mine serves as connections between different levels with the functions of ore-pass, manway, ventilation passage and for stope development. Inclined transport drifts are mainly used for: - communications and transport of personnel and material between horizontal levels. - transport of different equipment between mine areas and workshops underground. 2. DESIGN CONSIDERATIONS A space in an underground mine from which ore has been removed is called a stope. Depending upon conditions, stopes require varying amounts of support to prevent the earth and rock above from collapsing. In some mines, ore is extracted from several underground levels. In this case intervals must be left between the levels to prevent collapse. The stability of rock masses on which ore deposits occur in many cases determines the method of mining employed, although other factors may dictate the method used. Geological and rock mechanics data are the most reliable guides for evaluation of the adaptability of the mining methods to a given deposit. Ideally, a method of mining is employed that will yield the largest net financial return consistent with safety and optimum extraction of valuable minerals. Factors influencing the selection and design of underground mining layouts are as follows: 1  Production Settling pond Tailings Skip Ventilation Open pit shaft (mined out) Decline Abandoned Mined out and level backfilled Ore Sublevel pass Cage Producing Main level stopes Skip Haulage level Crusher Water basin Development Workshop, Ore Internal Pump station of stopes bin fuelling, Conveyor belt Ore Skip filling station Exploration Measuring Sump pocket Drilling Future reserves? © Atlas Copco Rock Drills AB, 2000 Figure 1a. A schematic view of an underground mine (After Hamrin, 2001). Figure 1b. A schematic view of an underground mine. 2 2.1. Rock Mechanics. The term rock mechanics is used to define the study of the behaviour of rock materials as they relate to man-made engineering projects that involve rock in place. Thus, studies are made of the physical properties of rock specimens that are taken from a rock mass. Many intact rocks behave elastically under load, and the theories of elasticity and the strength of materials are applied. Compressive and tensile strength are measured, as well as the strength under confining pressure. Dynamic rock mechanics deals largely with waves caused by explosives and their effect in rock breakage, with rock breakage in drilling, with mechanics of rock bursts (sudden collapses) and the effects of large, underground explosions. Methods have been devised to measure stresses, strains and displacements in rocks, both in open pits and underground. These studies are made to determine the stability of rock structures, support requirements, the behaviour of subsiding (settling) masses in caving and longwall methods of mining, and for increasing the efficiency and safety of mining. 2.2. Geological Features Geological details are carefully evaluated so that preliminary openings may be placed to best advantage, permanent openings may be placed in stable rock: stopes may be planned for optimum stability and ground control, mine openings may be maintained at minimum cost, underground water may be avoided, overall mining methods including caving procedures, may be planned; safety can be achieved. Geological features that influence the mining method include the size and shape of the ore body; the depth and type of overburden; the location, strike (horizontal course), and dip angle (the angle at which the deposit is inclined from the horizontal) of the deposit; the strength and physical character of the ore; the strength and physical character of the surrounding and overlying rock; the presence and absence of the aquifers (water carrying rocks); and the grade and type of the ore. 2.3. Engineering Design Factors Important factors in engineering design of underground mines include the strength of ore and wall rocks; shape, horizontal area and volume of the ore body, the thickness, the dip of the deposit; continuity of the ore; depth bellow surface, nature of the overburden; and position of the deposit relative to surface structures, drainage, and other mine openings. It is usually necessary to minimise those factors of lesser importance in order to satisfy the requirements of the more critical ones. The strength of both ores and wall rocks fixes the safe size of the openings, the length of time they will stand and the support required. Stability depends not only on the strength of the solid 3 rock but also on the existence of fractures, joints and other discontinuities and their geometric arrangement. Shapes of ore bodies vary from massive or tabular (having two parallel surfaces) and from bedded deposits to pipes, dykes (fissures in older rocks filled with igneous material), and sills (strata of igneous rock found between beds of other rock), depending on their origin and the character of the host rock structure. The attitude (inclination) of a deposit directly influences the mining method. A tabular deposit dipping at a high angle, for example, may be removed without use of supports if the walls are moderately strong. The roof of a similar deposit dipping at a low angle, however, may need support. A regularly shaped deposit may require less support. Mining operations in an irregular deposit will produce stopes with uneven walls, overhanging slabs, and projecting columns of wall rock that may require support if the rock is fractured or broken. A small ore body in strong rock may be mined without support, but larger ones in the same kind of groundmass may require supporting. There is a limit to the length or width of an unsupported rock arch or span that will posses sufficient strength to stand. Usually, as depth increases, a method must be changed because openings require more support. Shallow deposits are subject to relatively low overburden pressures. The vertical pressure on mine openings usually increases proportionally with depth. The direction of pressure in walls or roof of an excavation depends on the inclination of the ore deposit and local geological factors and must be considered in support desing, In a steeply dippong tabular deposit, waste (broken rock) filling will furnish adequate support against side preassure, whereas un a wide deposit, in which the driticl pressure acts downward, filling cannot be relied upon to prevent all movements. 2.4. Geology, Rock Structure and Geometry In addition to their value in exploration, geological theories of the genesis of the mineral deposits are also valuable guides in mine operation, influencing prospecting, exploration, development and exploitation. In prospecting, geology is a vital tool in finding new ore bodies and is most effective in the hands of an experienced mining geologist. In exploration and development, the mine engineer should have a knowledge of strength of materials, rock mechanics and of the structural features of the deposit that will affect the production of ore and the margin of profit. Most of these factors can be treated in only a semiquantitative manner, because the behaviour of the rock structure is complex. Design details may also be considered in relation to bedded deposits, veins and massive deposits. Bedded and sedimentary deposits that have not been disturbed by faulting, folding, or other action are, like flat-lying beds of coal, simple to mine. Support problems are often easily solved, and a systematic method of pillar support is employed. Poor rock in the immediate roof, 4 however, such as shale, creates hazardous conditions. The most serious problem in this type of mine may be determination of the number, size and position of pillars required for support. Many commercial mineral deposits are found in or closely associated with veins in fractures, shear, and fault zones. Deposits vary from tabular veins to pipelike bodies and shoots and may be regular or irregular, wide or narrow, continuous or discontinuous. Thus, many different methods are used to mine them. The large, disseminated copper-ore bodies of the western United States are typical massive deposits; those with enough overburden or capping to prohibit mining by open-pit methods are often mined by block-caving. Deposits of porphyry coppers are usually extensive, flat-lying and relative regular in outline; though low grade; their reserves are usually measured in millions of tons. The concentration of valuable minerals has been the result of geologic changes that left behind a weak, leached overlying rock mass. 3. UNDERGROUND MINING METHODS In underground mining, the intervals between different levels and the support systems employed must be carefully selected. Underground mining methods are often classied as:  Unsupported o Room and Pillar Mining – tabular, flat, thin, large size deposits o Open Stoping – tabular, steep, thick, large size deposits  Supported o Cut and Fill Stoping – variable shape, steep, thin, any size deposits o Drift and Fill Stoping – variable shape deposits  Caving o Longwall Mining - tabular, flat, thin, large size deposits o Sublevel Caving – tabular or massive, steep, thick, large size deposits o Block Caving - massive, steep, thick, large size deposits In ore deposits of hundreds of metres in vertical dimension, the interval between haulage levels should be the distance that gives the least cost per ton ore produced; that is, the value of ore to be mined from a given level must exceed cost of driving the level. The main cost items include sinking shafts and drifts; driving crosscuts to the ore; mining pillars; raises and ore passes needed; maintenance of drifts, crosscuts and raises for the life of the level; hoisting ore to the surface; pumping ; handling ore and supplies in stopes; ventilation; waste filling; and supervision. Underground openings where the rock in the roof and sidewalls is too weak to stand alone must be supported. Many modern shafts are circular; support may be provided with steel or 5 timber. Concrete may be used in shafts and permanent openings as well as steel sets. In very heavy ground, yielding steel arches or sets have been employed. Rock bolting has found broad application, particularly in openings that must be supported for long periods. A rock bolt is a steel rod, threaded on one end and provided with a means for anchoring in a hole in the rock on the other end. Rock bolts are employed in drifts and other types of openings to hold the rock structure together, to reinforce strata, and to hold key pieces of rock in place and thus stabilise the structure. A fine aggregate mixture of portland cement, sand and water called shotcrete may also be used to stabilise the rock around an opening when it is sprayed on in sufficient thickness. The shotcrete fills in small voids, holds key fragments in place, and furnishes arch support for the opening. It is used mostly in tunnels. 3.1 Room and Pillar Mining In room and pillar mining the ore is excavated as completely as possible leaving pillars to support the hanging wall. Pillars may be spaced regularly, as in deposits of salt or phosphate, or randomly spaced in irregularly occurring ore, and the method may be applied to either horizontal or inclined deposits. Its greatest application is in flat-lying, bedded deposits. The pillars are usually circular, square, or rectangular in section and flared at the top and bottom to increase contact area with the roof and floor. The ore left in the pillars is sometimes recovered later. In the development and mining of a flat-lying deposit, one or more openings are driven in a selected direction, and rooms are excavated usually at 90o to the openings. The pattern of layout of rooms may vary considerably, however. Pillar heights vary from a few to over 30 metres, depending upon the thickness of the deposit. Figure 2 shows a schematic layout for room and pillar mining. 6 Figure 2. Room and pillar mining layout (After Hamrin, 2001). Plate 1. Multi-boom drilling machine (Jumbo) 7  Plate 2. Remotely operated continuous miner in a coal room and pillar panel. 3.2 Open Stoping Pillars of ore or waste rock are left to support the back of stopes in deposits of low-grade ore in which it is cheaper to leave such pillars than to use artificial support. The required support depends on the depth of the deposit or the total weight on the pillars; the nature of the roof, which controls the length of unsupported span; the nature of the floor, which controls the bearing area and consequently the size of the pillar; and the strength of the ore, which determines the minimum size of pillars. This method is applicable to geologic conditions that require a minimum of artificial support, the walls and roof span or both being self-supporting. Small ore bodies may be mined from wall to wall without pillars. Where ore bodies are larger, pillars of ore are left to keep the roof span to a safe dimension. The size of open stopes vary from 10x10x10 m. (widthxdepthxheight) to very large openings (approximately 50x50x200 m.) as in the Mt Isa copper mine in Australia (Figure 3). Pillars left during mining may later be taken out (“robbed”) and the walls allowed to collapse. In relatively high grade orebodies or in areas where surface subsidence is to be avoided, open stopes are usually backfilled and the pillars are mined out (stope-backfill-stope-backfill). Plate 3 shows a load-haul-dump unit at the entrance of an open stope at the Hilton mine in Mt Isa. There are a number of variations of open stoping, these are: 8  3.2.1 Sublevel Open Stoping In sublevel open stoping the stopes are normally large in the vertical direction, and backfilled after mining. Drilling is carried out from sub-levels using 50 to 80mm diameter holes. The orebody is divided into separate stopes and pillars are left to support the hanging wall. Sublevel drifts for longhole drilling are prepared inside the orebody between the main levels. Vertical spacing between sublevels can be around 40 m. Drawpoints are excavated below the stope for safe mucking with LHDs (Figure 4a). 3.2.2 Large Diameter Blasthole Stoping In large diameter blasthole stoping sublevels are omited and longer blast holes of 100 to 200 mm are used. The depth of holes may Plate 3. An LHD entering an open stope at the reach 100m. Vertical spacing between Hilton Mine in Mt Isa Mines Australia. sublevels can be nearly 60 m (Figure 4b) Figure 3. Large scale open stope and fill schematic. Plate 4. Large diameter long hole drilling 9  (a) (b) Figure 4. (a) Sublevel open stope (b) Large diameter blasthole stope (After Hamrin, 2001). 3.2.3 Vertical Crater Retreat Vertical crater retreat (VCR) mining is used in steeply dipping competent ore and host rock. The method is based on the crater blasting technique in which powerful explosive charges are placed in large diameter (140 to 165 mm) blast holes and fired. Some of the blasted ore is left in the stope to provide support. The holes are drilled and charged from the overcut. The stopes may or may not be backfilled (Figures 4a and 4b) (a) (b) Figure 4. (a) VCR mining of primary stopes (b) VCR mining of secondary stopes after backfilling (After Hamrin, 2001). 10 3.3 Cut-and-fill Stoping In the cut-and-fill method the ore is removed in parallel or stepped horixontal slices, and as each slice is removed, a layer of waste (broken rock) fill is placed in the stope, leaving headroom above it. Its applicability is similar to that of shrinkage stoping. The ore must be strong so that the miners can work under it. The walls do not need to be as strong, since the fill provides support. The fill may be in the form of broken rock form the mine. In modern cut- and-fill however, the hydraulic filling method is normal practice. The filling material, consisting of fine grained tailings or sand mixed with water (and cement sometimes), is pumped through pipelines into the stopes and the water is drained off. Because it settles less, hydraulic fill is usually more satisfactory than broken rock. Cut-and-fill stoping permits sorting and mining of irregular deposits and dikes, ore dilution to a minimum. Ore production is intermittent, however, since filling is required, and the method is costly. Figure 5 illustrates a layout for cut-and-fill mining. Figure 5. Cut-and-fill mining layout (After Hamrin, 2001). 11  (a) (b) Plate 5. (a) A multi-boom drilling machine underground (b) View from the operator’s cabin 3.4 Sublevel Caving In sublevel caving the ore is divided in sublevels with 8-15 m vertical spacing. The sublevels are developed with a regular network of drifts, covering the whole area of the ore. From the drifts , the ore is drilled with a fan shaped pattern in an upward direction. Blasting of the fan starts at the hanging walls or at the end of the ore and proceeds towards the footwall or the ore pass. Several drifts and levels are worked simultaneously to keep an even retreating front. Sublevel caving is used in large, steeply dipping orebodies. The rock must be strong enough to allow the sublevel drifts to remain open. The hanging wall should fracture and collapse to follow the cave, and the ground over the orebody is allowed to subside. When a fan is blasted the ore caves into the drift, where it is loaded and transported to the ore passes. The hanging wall caves continuously and follows the extraction of ore. This causes a dilution of the ore which increases during the loading operation. When the dilution reaches a certain limit, loading is interrupted and a new fan blasted. The dilution may vary between 10 and 35% and the ore loss between 5 and 20%. Figure 6 shows the mining layout for sublevel caving. Kiruna iron ore mine in Sweden is and example of large scale highly mechanised sublevel caving operation as illustrated in Plate 6. 12  Figure 6. Mining layout for sublevel caving (After Hamrin, 2001). Plate 6. Sublevel caving layout and the caved area at the surface in Kiruna iron ore mine. 3.5 Block caving The block caving method evolved from the methods used to mine pillars in the Lake Superior iron mines. It is particularly applicable to very large ore bodies that have cappings that are sufficiently weak to be caved. Preliminary work consists of a series evenly spaced crosscuts below the level of the ore body, from which a series of raises, known as main, branch, and finger raises, are extended up into the ore. The mass of the ore is then weakened by undercutting, and side cutting is sometimes necessary. The ore is further weakened, usually by blasting, just above the point where the ore is drawn off. The high pressure created by gravity will crush the ore at the lower part of the block and give a fragmentation which allows the ore to be drawn from draw points. 13 Porphyry-copper and kimberlite deposits where both the ore and capping are weak lend themselves particularly to the block caving method. The cost of mining by block caving is low, approaching that for open-pit mining, and a high rate of production is attained once production is started. Mining conditions can be standardised, making for safe and efficient operation, and the accident rate is fairly low. On the other hand, capital expense is large, with a long period of time before a mine produces ore. Extracted ore is diluted with waste, and there is some loss of ore; drawing of the ore must be carefully controlled; and finally, low-grade ore in the capping and at the margin of the ore is lost. Figure 7 shows block caving mining layout. Figure 7. Block caving mining layout (After Hamrin, 2001). 14 Plate 7. A view of the caved area (mined out) from a the transport level at Premier Diamond mine, South Africa. Plate 7 shows the view of the caved area (mined out) from the transport level at the Premier Diamond mine, South Africa. Figure 8 illustrates the block cave design below the Palabora open pit copper mine in South Africa. Figure 8. Palabora block cave design. Plate 8. Palabora open pit before going U/G. Figure 9. Non-coal underground mining performance comparison. 15  Table 1. Non-coal underground mining price comparison (2019 prices). 3.6 Longwall Mining Longwall mining is applied to relatively thin tabular deposits such as coal. In longwall mining the ore is excavated in slices along a straight advancing or retreating front. The excavated area close to the production face is supported to provide space for mining operations and for safety. Further back, this area can be backfilled or allowed to cave. Mechanised mining of coal deposits using longwall techniques has improved production rates substantially during the last decade. Figure 10 illustrates a longwall coal mine layout. A detailed view of a longwall face with the roof supports and a power loader (shearer) is shown in Plate 9. Figure 10. Coal mine longwall face layout (After Hamrin, 2001). 16 Plate 9. Longwall face production showing the support system and thepower loader (shearer), and schematic face end control system. Plate 10. Coal mineface supports and a Roadheader used in face development Longwall mining is also applied in mining thin, reef type deposits such as the gold deposits in South Africa. Longwall mining in hard rock is often not fully mechanised, hand held pneumatic rock drills and single timber or hydraulic suports are used for production and support. Figure 11 illustrates a gold mine longwall layout. Plate 11 shows a conventional (not mechanised) longwall face at Mooinoi chromite mine in South Africa. 17  Figure 11 Longwall mining in gold reef. Plate 11 Conventional longwall face at Mooinoi chromite mine in South Africa. 4. MINE VENTILATION Underground mines must be adequately ventilated to provide sufficient oxygen to support life, to carry out noxious or explosive gases and to provide cool air in hot and humid mines. In gassy bituminous coal mines large amounts of air is required to dilute methane gas released from the coal. Noxious gases are generated in some metal mines by the action of acid water on rocks and minerals as well as by explosives used for blasting. Radon gas must be removed from uranium mines because of its radioactivity. Many mines are excavated in rock masses where the rock temperature is as high as 60° C or more. The air circulated through many such mines is cooled and dehumidified increasing the overall cost of ventilating these mines. The main ventilation system of a mine usually requires a minimum of two openings (Figure 12) to the surface, with a fan at one of them (Plate 12). Air may either be forced through the mine by a positive pressure or pulled through by exerting suction through one opening. The fresh air is guided through the mine by stoppings, doors, bulkheads or crossings. Auxiliary ventilation 18 by small fans and ventilation ducts picks up fresh air and forces it into the dead end drifts, raises, stopes and another areas that cannot be ventilated by the main air current. Figure 12 Underground coal mine layout whit two shafts and colour coding: Blue indicates fresh intake air and red indicates contaminated return air. (a) (b) Plate 12 (a) Main fans used to vente an underground mine, (b) hot, humid and contaminated air condensing as it exits the return shaft in a cold day. The cost of mine ventilation and air conditioning may constitute a significant proportion of the total production costs, thus affecting the cost of the final mine product to the consumer, the grade of mineral that can be mined, and the profit margin of the company. For primary ventilation of a mine, a fan must be chosen that will deliver the necessary volume of air at the required pressure. The volume of air a fan can deliver varies with the amount of resistance to airflow encountered in the mine. This resistance changes with the extent of excavation, so fans have been designed whose characteristics can be changed by altering the 19 pitch of their blades or the speed of the motor. Modern day mine ventilation is designed and optimised by the use of computer software which can help plan for future developments on a daily basis (Figure 13). (a) (b) Figure 13 (a) A computer generated sub-level stope design for a vein deposit and, (b) ventilation design representing the same mine generated using the RSM mine ventilation design software VentSim. 5. MINE PLANNING AND DESIGN Computers have been used in mine design for some time. As result, wide choice of software to help geology mappings, surveying, mine design, optimisation and scheduling applications has been developed and gathered under same name of Computer Aided Design (CAD). The development of computer aided design systems introduced the concepts of working with 3- dimensional (3D) graphics. Main components of modern mine design are: 1. Visualisation of the deposit from drill hole data and geologic interpretation, using all available information, including surface geology, geochemistry and geophysics; 2. Drawing of vertical and horizontal sections; 3. Contouring of deposit outlines and geological structure until the model represents best estimate of reality; 4. Estimation of grade and quality distribution; 5. Calculation of reserves; 6. Examination of possible mining methods; 7. Open pit and stope design; 8. Blast hole design; 9. Design of mine services (ventilation, transport, drainage etc.); 10. Determination of economic feasibility. Computer aided mine design starts with storing a vast amount of survey, sample and geology drillhole data into a common database. Subsequently, a various cross sections can be generated at any angle to the grid by extracting drillhole assays or geological data from the 20 database (Figure 14). Displaying assays and geology along the drill holes, enables user to outline the ore zones and establishes base for building a geological model. Figure 14 Exploration drilling and assay data represented in mine design software. (a) (b) Figure 15 (a) An example block model showing grade distribution in different colours, (b) an open pit design for an irregular orebody. (a) (b) Figure 16 Example mine design representations (a) a vein trype orebody accesed by a shaft and a series of sublevel drives, (b) a massive orebody and a ramp acces. 21 There is a number of different modelling techniques which are currently in use, such as block modelling and wireframe or string modelling. In block modelling the orebody is represented by a point value typically at the centre of the block. This point value has assigned to it the attributes of the ore for the volume of material represented by the block, and is stored in the computer as a set of X, Y, Z co-ordinates, and a set of attributes (Figure 15). Typically in an open pit the block is assigned a Z dimension equal to the bench height. Wireframe model is build by combining a number of sections and plans drawn through ore body. This layered model is not truly three dimensional, but in fact represents the perception the mining engineer has of the orebody in many mining operations. Once a valid geologic model is established, next step is to define mine limits, according to the appropriate parameters. These limits may be geological, property lease limits or some combination of cost factors giving an economic limit. With this rough mine limit it is possible to start detail mine design depending on a type of operation, i.e. underground or open pit mining (Figures 15 and 16). Various optimisation techniques can be employed in order to produce optimal mine contours. Furthermore ore outlines, coming from either a block model or a structurally controlled model can be viewed during design. Chosen optimal mine design is followed by short and long term scheduling. REFERENCES Atlas Copco, 2007: Mining Methods in Underground Mining, Second Eddition, Second edition www.atlascopco.com Hamrin, H. O., 2001: Underground Mining Methods and Application In Underground Mining Methods: Engineering Fundamentals and International Case Studies, Hustrulid, W. A. and Bullock R. L. (Eds.), Society for Mining, Metallurgy and Exploration, Inc., Littleton, Colorado. 22 GLOSSARY Blast A production BLOCK in which BLAST HOLES have been drilled. Blasthole A blast-hole is drilled for the primary purpose of placing explosive to break rock or ore. Blasting Pattern Designed or actual pattern of BLAST-HOLES; they may lie on a regular or irregular grid for a surface mine, or may represent a fan of drillholes for an underground mine. Drift An inclined ACCESS ROUTE into an underground MINE. Drive Sub-horizontal ACCESS ROUTE to an underground mine. Exploitation Method The exploitation method is simply the method by which a deposit is worked - whether it be open-pit or underground, and the specific type of geometry and MINING SEQUENCE to be used. Grade The concentration of a mineral in a mine or piece of rock. Hanging Wall/Footwall Volume above/below FAULT or ORE BODY. Superseded by BODY WALL Haul road A road going from an ORE-BODY excavation to some storage/transportation/processing location Superseded by ACCESS ROUTE Mine A system for extracting mineral resources from the ground Mine Layout MAP (possibly 3d) of a MINE Mining Block Basic unit of mine estimation. Mining Sequence Plan for production of minerals from a deposit within a defined mine design, allocating mining units to calendar intervals. Ore An economically mineable mineral. Orebody Envelope of ORE ZONES. Overbreak The rock which is broken (and sometimes must be excavated) by blasting outside the intended area or line of break. Overbreak may occur as a result or misalignment or unintentional overcharging of blastholes or intentionally overbreaking as in the toe of a bench face to facilitate digging to grade.. 23 Rail haulage system Material transportation system consisting of gondola cars, and the steel rails on which the cars are moved about which a suitably powered traction unit as a locomotive. Sampling Pattern A sampling pattern is defined as a series of SAMPLES designed to define or test the geochemical composition of a given area. Shaft A vertical ACCESS ROUTE in an underground MINE Underground Layout A definition of the openings in an underground MINE including positions of SHAFTS and tunnels and locations of the individual extraction locations (STOPES , longwall faces, rooms and pillars, etc.) dependent on the mining method which is planned, positions of ramps. Vein A vein is defined as a mineral filling of a FAULT, FRACTURE or CLEAVAGE. 24