- Programme of Study and Description of Mining Methods
To give a sufficiently full characterization of a mining methods actually employed or planned, one should study it and, if necessary, describe it in many of its aspects. The pertaining data and characteristics may be classified into the following groups.
I. Mining and Geological Conditions
Name of the mineral extracted. Shape of the deposit-bed, sheet like deposit, placer, vein, etc. Thickness of the deposit ( true and lateral ), prevalent thickness, maximal and minimal deviations. Angle of dip and its variations. Pitch or hade of the ore body. Area of the horizontal section of the deposit. Typical geological faults and disturbances in the attitude. Matter composition of the minerals. Distribution of useful components in the deposit. The nature of the contact between the deposit and the country rocks surrounding it. Hardness, jointing and firmness of the mineral. Its density ( volume or unit weight ). Size distribution and ability to compact. Petrographic characteristics of enclosing country rocks. Their hardness, jointing and stability. Abudance of water in the deposit. Properties of the mineral’s self-ignition. Oxidability of the ores subject to flotation. Evolution of noxious gases. Harmful properties of dust ( explosiveness of coal and sulphide dust, dangerous properties of quartz dust with respect to silicosis ).
II. Mining Characteristics of the Method To Be Adopted in Working a Deposit
Designation of the mining method. Level interval. Sublevel interval. Extent of the working section or block on strike. Size of pillars and support pillars. Slice thickness. Cross-section and support of development openings. Sequence of driving development openings. Advance rate of faces. Rate of development headings advance over that of production faces. Order of recovery of mineral reserves in a working section or block. Order of mining sublevels, pillars or slices. Shape and size of working faces. Their interlocation. Advance direction of working faces. Method of stoping. Methods of controlling enclosing rocks ; by support pillars, timbering, filling ( complete, partial ), shrinkage stoping, caving ( spontaneous or induced ), or by different combinations of these methods. Methgrizzly levels ( in ore mining ). Ventilation of development and productive workings. Lighting of mine workings. Measures envisaged by the system of mining against penetration of water and inrushes of water-bearing rocks. Preventive measures against underground fires, as part of the mining method adopted.
III. Mechanisation of Mining Operations
Brief specifications of machines (trade-mark, capacity, ratings of driving motors and overall dimensions) used for drilling holes, undercutting and breaking the mineral or country rock: drilling machines, electric augers, drill-wagons for the underground boring of deep blast-holes and large diameter holes; coal cutters, cutting and loading machines(combines), coal planers, hydraulic giants(in hydraulicking),etc. analogous information on machines and equipment employed for the transportation of the mineral and waste: conveyers, scrapers, loading machines, mine car spotting tugger hoists, district electric locomotives, capacity and overall dimensions of mine cars. Machines and mechanical plants for ventilation and mine drainage(needed for the system of mining).
IV. Organisation of Work
Organisation of operations in the faces of development and productive workings. Graphs (planograms) of cyclic operation and labour distribution charts(number of miners, number engaged in each shift and classes of work performed). Advance rate of faces per cycle or round. Number of cycles or rounds per day and per month. Coordination of all operations for the whole of the producting section( linked with the system of mining ).
V. Techincal and Economic Characteristics of the Mining Method
Mineral output in productive and development workings per day per shift, in individual faces ( walls, stopes ) and in the section as a whole. Monthly tonnage produced by the entire section. ( If, because of features specific to the adopted method, the tonnages tend periodically to very widely, for instance, during shrinkage-stoping and subsequent drawing of the ore, the characteristics above must be given for individual stages of mining ). Yield of the mineral from development and working faces(for the whole of the mining method in per cent). Mining of working losses of the mineral( in per cent ). Degree of dilution (in per cent to the total content of valuable components in undiluted ore). Time required for the recovery of the aggregate reserves in the working section or block. Output per faceman and per miner for the whole of the section (in tons of mineral, or in cu m of ore, or ore and barren rock together per shift). Explosives consumption per ton, or per cu m in grammes. Mine timber consumption per 1,000 tons or 1,000 cu m of the mineral, or the aggregate amount of the mineral and waste. Electric power and compressed air consumption per ton or cu m. mining cost of a ton or cu m of the mineral, or of the mineral and waste together for the whole of the producting section, including delivery to the haulageway.
- Classification of Mining Methods
Methods employed for mining solid minerals in deposits may be divided into the following principal groups :
I. Underground mining.
II. Surface mining.
III. Combined mining.
IV. Special methods of mining.
No explanations are needed for singling out methods I and II. One example of method III is mining by glory holes, when the mineral is extracted by the opencast method and loaded into transport vehicles and subsequently hauled in underground workings.
Special methods include those in which actual mining is characterized by changes in the native state of the extracted mineral. They include underground coal gasification, ore-mining by underground leaching, extraction of sulphur through boreholes by evaporation, etc.
As we have seen, the systems used in mining solid minerals by the underground method vary widely and are frequently complex. For a more or less full characterization, one should refer to many of the features enumerated above.
However, the classification of mining methods cannot be founded on all the above-cited, extremely numerous features. Their classification should be based only on the especially important and typicalfeatures, according to which it is advisable to divide and single out the systems of mining.
Most of the hitherto proposed classifications of mining methods were based on methods of controlling enclosing rocks and on the arrangement of development openings.
It is noteworthy in this connection that the division of mining methods into groups according to the arrangement of development openings is generally adopted both for drawing up classifications and for working coal and other sheet deposits, whereas the classifications for the systems applied in mining ore deposits are founded on the second principle-that involving the method of enclosing rock control. This difference in the approach to the characteristic features, on which the classification is based, is by no means accidental or one chosen arbitrarily by the compilers of the classification, but is explained by the fact that for the sheetlike deposits the arrangement of development openings is very typical and at the same time simple and convenient because of their regular shape.
- Choice of Mining ethod
The description of the principal methods of mining enumerated the conditions most suitable for each. But since the combinations of diverse factors in enfluencing the selection of a mining method may be extremely variable, this choice for a particular deposit is complicated by its geological features, as well as by the mining and economic situation.
The method selected must meet the basic demands of the conditions in which it is called to operate.
In a very general outline the method of the choice itself boils down to comparing the features of each one of the mining systems which may possibly be employed in actual geological, mining and economic conditions.