1、 中文 2975 字 英文原文 PROSPECTS ESTIMATION OF KNOWN SYSTEMS APPLICATION FOR COAL SEAMS MINING AT GREAT DERTH Prof.w.p.Zubov Leningrad Mining Institute Abstract： Estimation of present and future situation in technological schemes on coal mining at great depth applying highly productive mechanized complexes
2、 is presented here, Stis shown that the decrease both in operation concentration and the share of pillar mining at deep mines is connected with increasing difficulties in development working support behind the face as well as prevention of roof caving in face area. Introduction： Underground coal min
3、ing efficiency depends at Iarge extent on technical economic indices of deep mines, the level of their development being steadily increased. In transition to deeper levels specific expenditures increase parallel with the deterioration of geological conditions in coal seams mining. At mines of Donets
4、k basin where seams are mined at a depth of 500m ad more, the depth increase for every 100m results in production cost to 3-4%,here labour productivity of miners decreases in 6-8%1. One of the main effective ways to neutralize negative depth influence on under-round coal mining efficiency is to incr
5、ease average daily face output on the basis of using complex mechanization in stopping. At non-gassy mines the application of long pillar mining leads to face output in 1.2-1.65 times compared to average daily face output in longwall combined methods. Even more effective appeared to be long pillar m
6、ining in stopping under condition characterized by increased gas emission in goaf. In gassy mines the face output is determined taking into account the requirement of methane dilution up to permissible concentration, with methane emitting into ventilation current. In long wall and combined methods t
7、he intake air should enter the face along one of the development workings and the return air runs along the other development working. Maximum intake air quantity to the stope depends on both air current veloclty, regulated by safe security rules in working area and cross section area of the face wh
8、ich is free for air current passage. The factors mentioned above being of non-regulated nature, if becomes practically impossible to increase the quantity of intake air to he panel. According to the reasons discussed at mines with increased methane emission the actual average daily face output in lo
9、ngwall and combined methods in 3-5 times less than the face output level which may be reached using in full modern highly productive methods of mining. The application of long pillar mining permits prior to stopping to carry on some measures for seam degasification and use more effective schemes of
10、panel ventilation. Thus in applying both long pillar mining in the variant “face-sub-panel” and in shuttle scheme of panel ventilation relatively high face output (1000-1500t/day)may be reached at mines with relative gas emission up to 15m3/t, as well as at mines with higher gas emission when methan
11、e does not emit from the goaf. In estimating the prospects of long pillar and longwall mining as the space and plan basis for technological schemes in stopping operations at great depths, it is also necessary to evaluate the following factors. With the increase of coal seams depth, the methane conte
12、nt both in workings and in seams changes according to hyperbolic curve approaching to some limited value. The stronger influence of depth is more evident in gassy zones associated with developed areas of coal-bearing deposits containing seams composed of coal marks, high collector properties of coal
13、-earing measures and, hence ,the propogatlon of gas zone emission to greater depth are responsible for this. The mentioned regularity of methane-bearing capacity change in workings of Donetsk basin is also notieed at mines of Donetsk-Makeevsk, krasnoarmelsk, Almazno-Marjevsk,Voroshllov-gradsk and kr
14、asnodonsk geological and industrial regions. In the regions where antracite groups 11A-12A occur lower than the zones of gas emission, natural gas content increases at first up to maximum and then decreases sharply in values typical for zones of gas ecmission 2. Such character of natural gas content
15、 change marked for measures C of Torezsk-Snezhnyansk region and measures C of Bokovo-Chrustalsk geological-industrial region may be explained by the increase of metmorphism grade of antracite seams with the depth increase. Practically speaking in donetsk basin methane content of seams is not traced
16、onlyin its southeastern parts, where the seams up to a bepth of 1600 m are represented by high metamorntosed antracites. Therefore, in the nearest future gas factor influence on economic efficiency of underground coal mining will be increasing in the USSR.Taking into account good results achieved by
17、 known ways of preliminary seams gasitication, it should be assumed that the most negative influence of operation effioncy with wide use of long pillar mining will be in mines where gas emission in more can 15 m3 per ton of daily output. Donetsk basin illustrates the tendency of this factor with dep
18、th increase, there the number of highly categorized mines in 1940 was 17%, in 1970-45%, in 1980-60%, in the late 1987-68.8%, the average depth of coping during the period studied increased from 198 to 659. The fact that gas emission from the developed area increases panel gas balance depth deserves
19、special attention in estimating some prospects of longwall. Thus, in Donetsk basin a coal seam up to 600 m depth becomes the main source of gas emitting into stopes and development workings, methane emission from the coal seam is 40-50%and in some cases up to 20% of total gas emission volume in tran
20、sltion of mining operations to a depth of 700-1000m. Besides at deep levels the preliminary degasification efficiency of measures on seam degasification by common methods is not more than 15-30% at great depths. However, the required decrease of gas emission in workings should be not less than 60-70
21、%, here the restrictions on gas factors being lifted. Thus gas emission from the developed area becomes the main factor determining maximum face output in seam mining at great depths. Under these conditions to solve the problem of panels ventilation only by seam degasification measures seems impossi
22、ble. In highly categorized mines with gas emission not more than 40% during stopping some restricting on ventilation can be overcome only be applying direct scheme of panel ventilation with return air freshing in goaf. But this scheme of ventilation is practically realized only in pillar mining. The
23、 facts mentioned above indicate that the increased application of pillar mining combined with direct ventilation schemes should be considered as priomising and economically proved. It perfects deep mining when highly productive mechanized mechanized complexes are used. Though in Donetsk mines the pr
24、oblem concerning the average daily face output increase is acute, the share of pillar mining comprises not more than 43%, including about 10% of pillar mining with direct panel ventilation. Moreover, with depth there is a strong tendency of decreasing the number of faces developed by pillar mining.
25、Thus in “Makeevugol” mines the share of pillar mining decreased from 60 to 35% during the period of 1975-1985. The average depth of mining during this period increased in 276m, being 860m in 1985. As a whole in Donetsk basin the share of pillar mining in mines extracting seams at depths up to 600m i
26、s 48.2%, at depths of 600-1000m it is 40.2% and at depths more than 1000m it is not more than 19%.Now at deep levels long wall and combined methods of mining in the so-called “single face” variety are widely used. Long wall and combined (in the shape of) methods prevail in deep mines of FRG. In the late 1985 their share in the number of faces was more than 65%, as to their share in the overall mining of commercial coal it was 62.2%3.
