Contour Mining

Contour mining occurs on hilly or mountainous terrain, where workers use excavation equipment to cut into the hillside along its contour to remove the overlying rock and then mine the coal. 

The earth (overburden) overlying the coal may be removed by shovel, dragline, scraper, or bulldozer, depending on the depth and overburden character. The overburden is cast (spoiled) downhill from this first pit, after which the exposed coal is then loaded into trucks and removed from the pit. A second pit can be excavated by placing the overburden from it into the first pit. 

Succeeding pits, if any, would follow in the same sequence, with the amount of overburden increasing for each succeeding pit until the economic limit of the operation, or the maximum depth limit of the overburden machine, is reached. This economic limit is determined by many variables. 

FIGURE 5.17 Potential for water contamination from mining operations. 

When the mining operation reaches a predetermined stripping ratio (tons of overburden/tons of coal), it is not profitable to continue and depending on the equipment available it may not be technically feasible to exceed a certain height of high wall. 

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Contour mining is used in hilly areas, where the slope of the surface will permit only a narrow bench cut around the side of a hill the excavation is backfilled immediately after the removal of coal. It is the only method that can be used on slopes of 15 degrees or higher. 

Auger mining is a supplementary method used to reach coal in stripped areas where the overburden has become too thick to be removed economically. Large augers are operated from the floor of the surface mine and bore horizontally into the coal face to produce some reserves not otherwise minable. This technique is frequently used to supplement coal recovery from contour mining. 

Contour mining (contour stripping) The removal of overburden and mining from a coal seam that outcrops or approaches the surface at approximately the same elevation in steep or mountainous areas. 

Surface mining techniques are used when the coal is present near the surface, and the overburden is thin enough. These techniques include contour mining, strip mining, and auger mining. 

This has been a bugbear all along, and in the early 1990s we tried to establish how the contours of detection around a buried mine, or mines, looked. The shape we established, I described later, could be as irregular as a camouflage pattern. 

Groenewold, G. H. Rehm, B. W. 1982. Instability of contoured surface-mined landscapes in the northern Great Plains causes and implications. 

Fig. 3. Early method of contour surface mining. This was the predominant way of mining throughout Appalachia until passage of stringent legislation that ushered in a new integrated mining technique. [Caterpillar Ini)...

Explosives. Preliminary removal of the HE charge from the mine, proj or shell usually involves the use of hot w or steam to liquefy the expl which is then separated from the w by gravity (Refs 1 thru 5), or contour drilling followed by high pressure w erosion to remove the HE residue (Ref 27). The new concept of ammo which can be readily recycled by design, however, has resulted in the prepackaging or encapsulation of the entire HE charge for easy and safe removal (Ref 24). 

Bench surface of an excavated area at some point between the material being mined and the original surface of the ground, on which equipment can sit, move, or operate. A working road or base below a high wall, as in contour stripping for coal. 

Strip mines consist of shallow excavations, perhaps 109 yd (100 m) or less, that are used to mine tabular bodies of rock such as coal. Soil and rock above the mined material, known as overburden, are removed and set aside. Because the strip mines consist of shallow excavations, the overburden can be economically replaced, re-contoured to resemble the original topography, and replanted. 

Assumptions about the basic method of disposal of the coal-cleaning waste must be made. For this paper, we assumed that the valley-fill method would be used. In this method, a narrow downward-sloping valley near the cleaning plant is filled, in benches, from the upper end. As the upper benches reach contour level, the pile is covered with sufficient soil to retard water percolation to one-third that of an uncovered pile. The drainage from such a waste pile has the characteristics of acid mine drainage, with most of the dissolved solids being iron sulfates. 

The mining of bauxite for an alumina product has the same kind and degree of environmental impact as imposed by any strip mining operation. These effects may be minimized by spoils replacement and aesthetic contouring, as well as by the replanting of hardy grasses and shrubs, where appropriate. 

Disposal of the waste pulverized gangue may be to underground or strip mined areas. However, excess disposal volumes can be a problem. Dry land disposal followed by aesthetic contouring and reestablishment of plant life may be used. This method requires monitoring and control measures for any dissolved metals in leachate from the tailings. Drainage directly to a small lake or a water course is not permitted by pollution control agencies (e.g. [28]). 

Manage the waste dumps as required by contouring waste piles to stable configuration or returning waste to mine workings for use in reclamation. Prepare mine workings for reclamation by... 

Fig. 4. Location map of the sampled subsurface leaks from the Belle Isle salt mine, also showing the approximate outline of the mine superimposed upon the structure contours on the salt top of the Belle Isle dome. (Not shown are several past leaks reportedly in the middle of the mine.)...

Fig. 5. Structure contours on the salt top of Weeks Island dome with the approximate outline of the salt mine workings heavy line bounding the stippled area).

Chemical contour maps (or bench maps) are made for the purpose of selective mining of the ore. The chemical contour map is formed by correlating the drill... 

Figure 9.2 Process latitude (in terms of overlap depth of focus for 0.5- jLm lines patterned with Mine lithography) of UCB-JSR 1x500 resist with and without AZ Aquatar top antireflection coatings. Shown are the contour plots for the O.S-fjim line as a function of focus and exposure dose. ...

Figure 3. Velocity (m/s) contours during model outburst when mining through weak fault...

In the coal mine, the fault structure in Local areas developed and the roof was broken. If the overburden is aquifer, then water in fissure will develop. Then here shows that the amplitude contour fluctuation will be increased in the apparent resistivity contour map, the change of regional variation of apparent resistivity will be larger, and there will be discontinuous small scope in low resistivity zone. 

Different inlet and return air pressure are carried out for four U-shaped ventilation experiments. Along goaf tendency the distance for x = 0 cm side is the inlet side, and x = 160 side is the return air-side. The mined negative pressure and gas content for each point are tested respectively. Use MAT-LAB to analyze the pressure and gas concentration values and draw a three-dimensional contour map. The conditions of the gas concentration and pressure distribution get under differential pressure between inlet and return airway. 

Once the hill slope prevents further cutting into the hillside, miners often switch to a technique known as auger mining to extract more coal along the contour. 

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