Mineable coal

Table I shows the raw bituminous coal resources figures in millions of metric tons at various ash contents (2). The total figure of 81,274 million metric tons is for the total resources of raw bituminous coal mineable in situ down to 300 meters.

Figure 4 illustrates the coals of the Lower Kittanning formation in the Houtzdale quadrangle. In much of western Pennsylvania only one coal is mined as the Lower Kittanning coal (Figure 1). Here, however, there are five beds which may be mineable, at least locally. Most of the beds differ from...

The brown coal reserves in the Federal Republic of Germany amount to approx. 56 billion metric tons, 55 billion metric tons of which are in the Rhenish brown coal district located west of Cologne. About 35 billion metric tons of that reserve are considered to be technologically and economically mineable today (1). 

Preliminary studies by the Bureau of Mines estimate that there are 251 billion tons of low sulfur coal reserves (mineable coal) at less than 1000 ft in depth, of which an estimated 198 billion tons are in the West and 53 billion tons east of the Mississippi River. Of these totals, 30 billion tons are considered to be low sulfur strippable reserves in the West at less than 100 ft deep and 2 billion tons in the East. Preponderantly, however, low sulfur reserves are at depths which would require underground mining. Approximately 50% of these quantities is recoverable in mining. Supplemental surveys and analyses are being made by the Bureau of Mines of low sulfur coal reserves and production, separately for both the Appalachian region and the rest of the country. 

From old to new, the layers within the research area are Ordovician system. Carboniferous system, Permian system, Triassic system. Tertiary system and Quaternary system. The coal-bearing stratum is Permo-Carboniferous system The thin seam of carboniferous Taiyuan group system is nonproductive. The Permian system contains main productive coal seams including 33 coal seams, the primary mineable coal bed are 13-1, 11-2, 8, 4 and 1. 

The maximum trend length in 131419 of Laowuji Coal Mine is 1053 meters, the minimum trend length is 1030 meters, and the average trend length is 1042 meters. The thickness of mineable coal averaged at 2.8 meters and the dip of the coal averaged at 10°. The capability is 1.5t/ml... 

All mineable coal seams are located under the Ordovician limestone karst fracture aquifer which water level is 801.47 m (the pumping data of the 14 drilling). We can analyse the influences of the Ordovician limestone karst water to all mineable coal seams according to the coefficient of water inrush. 

From shallow to deep within 100 metres, Ordovician top strata can be divided into four zones based on water transmissibility. They are weak zone /, strong zone II, moderate zone III and weak zone IV. Usually Zone 7, with the shortest distance to the Carboniferous primary mineable coal seam, can be used as the key impermeable layer. Furthermore, zone II and III can be used as a goal target for preventing water disaster, also for developing and utilizing the water resources. 

It is fortunate that the techniques acquired are of considerable value for all aspects of exploration drilling and many of the new tools used in mineral exploration are now being employed to improve drilling performance in the rapidly expanding search for, and delineation of, mineable coal beds. Indeed, the utilization of oilfield rig equipment and technology has added an extra dimension in the search for coal deposits (Ezra, 1976 Pidskalny, 1979). 

The percentage of coal recovered from a mineable seam depends on several factors, such as the number and size of protective pillars of coal thought necessary to support the roof safely, and of the percentage of pillar recovery. In general, the less coal that is extracted the less is the need for costly roof supports. The necessity to protect valuable surface land also has a bearing on the amount of coal mined. In some areas where the surface land is owned by the coal producer, most of the available coal can be mined, whereas in other areas a lesser percentage of the coal is mined to prevent surface damage from subsidence. 

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