1、英文INFLUENCE OF TOP COAL HEIGHT ON THE PERFORMANCES OF TOP COALCAVING MINING METHODS IN JIU VALLEY COAL BASINProf. Dumitru BADULESCU, Min.Eng.Ph.D*, Prof. Ilie ONICA, Min.Eng.Ph.D*Taking into account the market economy concepts, beginning with 1995, the National Hard Coal Company of Petrosani (Romani
2、a) replaced the old mining methods with low pro-ductivity with others with higher productivity named top coal caving mining methods. This paper presents some ways of improving these methods in view of increasing the efficiency rate and the work security degree.Keywords: Conditions, mining technology
3、, coal drawing, analysis solutionStarting with the necessity of increasing the work productivity and diminishing the coal costs at Company level, the Jiu Valley mines activity became competitive, even in the year 1995, the changing process of the old methods with the top coal caving mining methods h
4、ad already begun.It is known that this high productivity min-ing method is applied in the conditions of the thick coal seams with all dips and configura-tions in several countries as: Independent States Community, China, India, France, Ca-nada, Japan, Turkey, ancient Yugoslavia, Hungary, etc.In the
5、real conditions of the Jiu Valley coal basin, the use of the top coal caving mining methods led to a doubling of coal productivity by rapport to the caving methods in slices, reaching the 12-16 tonnes per shift and coal face layout reaching 1200 tonnes per day.Depending on the geo mining conditions
6、this method is applied in several variants, depending on the thickness and dip coal seams 6, 9, 10.The mining technology used is the classical one, respectively top coal caving mining tech-nology with hydraulically props and articulated beams.The top coal height, for the Jiu Valley basin, ranges bet
7、ween 4.5m and 30m, arbitrarily cho-sen, on the basis of practical experiments.The top coal height is the most important parameter, which has the biggest influence on the technical and economical performances of the coal faces. Therefore, it is necessary to de-sign the top coal height after the scien
8、tific crite-ria, taking into account the coal and roof rocks characteristics.If wrongly applied, these mining methods led in some cases to an appearance of potential dangers linked to the: methane gas accumula-tion, endogenous fires (because the important coal looses in the gob area), the big voids
9、formed in the broken rocks, high mining pres-sures developed surrounding the face (because the low speed face advancement, less 5-7m/ month).The height of the top coal caving must be correlated with the provided coal output, the face advancement speed and the coal caviabil-ity.As the measure of the
10、top coal height is increasing, the face advancement speed is de-creasing, at the same time with the probability of danger occurrence. In return, a great size of the top coal leads to a reducing of the preparatory workings indicators.Contrariwise, if the top coal height is less, the dilution is incre
11、ased due to the broken rocks appearance in the drawing doors.The speciality literature is not very abundant concerning the top coal design, nor concerning similar conditions of Jiu Valley coal basin.Until the present time, a unique methodology regarding the top coal height determination has not exis
12、ted, but only specific tests for some coal deposits and which take into consideration only a certain number of parameters.Some researchers attempted to determine the top coal height depending on the economical criterion 6 and after the stability criterion 9, 10, 11.With the aid of obtained relations
13、 11, an abacus for the general case of coal seam no.3 of Jiu Valley coal basin and for the special case of Lupeni mine was elaborated 9, 10, 11.The top coal height determined following the geomechanical principle is lower (3.5-11m) than these practiced at Lupeni mine (10-30m).The mining methods of t
14、hick coal seams ofJiu Valley coal basin 6, 8 or a bituminous shale2, 5 is similar with those used for the ore bodiesmined with the sublevel caving mining methods.It is known that in the case of ore bodiessublevel mining methods, the broken ore draw-ing in the mining panel limits is one of the mostim
15、portant operations. The dilution and the orerecovery rate depend on this operation 1, 4.Also, the broken top coal drawing, respec-tively the control of the gravitational broken coaland rocks flowing phenomenon represents themost important operation of the technologicalprocess of top coal mining.The
16、principles and the flowing theory in thecase of mentioned mining methods are alsoknown 1, 9 and were developed to describe thefriable mediums flowing. The results obtained inthe case of underground mining of bituminousshale from the Anina basin 2, 3, 5, could beextrapolated for the case of Jiu Valley coal basin.The top coal height influence on the flowing,drawing, recovery rate and dilution of coal re-presents a problem too di
