1、翻译部分 英文原文： INFLUENCE OF TREMORS INDUCED BY MINING ON THE LIBERATION OF METHANE IN TO WORKINGS Krzysztof OGIEGO, Mieczysaw LUBRYKA, Jan KUTKOWSKI Jas-Mos” Coal Mine, Jastrzbie Zdrj Jzef SUKOWSKI, The Silesian University of Technology, Gliwice, Poland Abstract Methane which appears in the workings com
2、es from excavated coal, side walls, free faces and from basins in the surrounding rock mass such as adjoining coal beds and Weber goafs. Liberation of methane takes place through fissures and through porous and easily permeable rock layers. Simultaneous overlapping of the influences of mining fronts
3、 leads to increase in liberation of methane as a result of appearance of rock mass distressing. Coal bed mining at deeper level induces also tremors which can be followed by cracking of rock layers situated either in the close neighbourhood or in a distance from the workings. The existed fissures i.
4、e. fault fissures and those connected with the prior loosening of the roof layers or floor layers while mining the coal bed. Several examples from the practise of mining prove that there is relation between the occurrence of increased methane hazard in the workings and the energy of mining tremor, a
5、s well as horizontal distance of the evaluated tremor focal point. Tremor can be the cause of intensified liberation of methane into the workings and increase of methane concentration in the mine air exceeding the acceptable value if ventilation parameters are not readjusted to the amount of the met
6、hane outflow. Confirmed association of methane and tremor hazards justify the need of proper prevention in order to eliminate disturbance in ventilation of workings. 1. Introduction Association of natural hazards in the past was searched mainly considering the following systems: - mining tremor rock
7、 bump - rock bump methane liberation coal dust explosion - rock bump spontaneous fire - methane explosion coal dust explosion. At the beginning of the 90s the attention was also drawn to the system of mining tremor methane liberation type 4. The co-occurrence of such system of hazards had also taken
8、 place before, but there was no data about their number, frequency or range. This paper is a result of a few years observation of cases when sudden increase in methane concentration appears in the seams with seismic activity, after mining tremors. The observation focused on searching causal connecti
9、ons between sudden increase in methane concentration in the working and the tremor that had just happened, especially on searching quantity relations. To this end, about 3500 tremors were observed. The energy of the tremors ranged from 103J to 107J and they happened in 12 longwalls driven with roof
10、fall, in 10 longwall driven with stowing and in 8 heading faces in the 6 mines of Coal Basin of Rybnik. Apart from the energy of the tremor, such parameters as horizontal location of tremor focal point, speed of steam mining, seam methane content and number of tremors were taken into consideration.
11、The analysis of the relationship between the increase in methane concentration in workings and the above mentioned parameters may show directions for actions preventing dangerous effects of methane emission after the tremor. Methane emission after the tremor happens as an effect of rock mass crackin
12、g around the mine working. Work of fissures i.e. opening or clamping of cracks causes that methane included in the fissures flows out into the mine workings according to the pressure gradient. The observation has also revealed some cases when methane emission happened before the tremor. Such phenome
13、non can happen as a consequence of deformation processes that occur during seam mining, which in the final period may result in the tremor after methane liberation 7,8. 2. The influence of mine tremor energy on methane emission into the mine working The registered parameter which characterises scale
14、 of the tremor is its energy. During the seam mining the quantity of the released energy depends mainly on: - seam or mining port thickness - way of roof control - speed of mining. The sum of energy revealed from the rocks increases with the depth of mining, but the size of portions of revealing is
15、also important 2. In the observed mines low-energy tremors were connected with rock mass cracking in the close neighbourhood of workings. Focal points of the tremors occurred near working front and moved with it. Focal points of high-energy tremors of 106-107J occurred, in most cases, in significant
16、 distance from mining front and were connected mainly with the geological discontinuity. Therefore, it was difficult to find out the direct causal connection between the occurrence of high-energy tremors and methane emission into the mine workings. However, lower-energy tremors preceded the emission
17、 of bigger amount of methane into the near workings, which was registered as increase in methane concentration. It took place in 1015% of monitored cases of tremors. In most cases tremors did not cause methane emission into the workings, which would lead to increase in its concentration by at least
18、50% of the value registered before the tremor. The average growth in methane concentration after tremors of different energy is presented in Figure 1. In the figure, methane content of seams where the mining took place, is also differentiated. Part of the results was obtained from the seams included
19、 in II category (2,5 4,5 m3CH4/Mg) and the rest from the seams of IV category (above 8 m3CH4/Mg). As Figure 1 shows, in the interval of 102 105J tremor energy does not influence the amount of increase of methane concentration in the nearby workings. Fig.1 Influence of tremor energy on average increa
20、se in methane concentration in the nearby workings 3. The influence of the place of mine tremor occurrence on increase in methane concentration in workings in the observed area The results of mine tremors observation on the selected seams enabled to evaluate the influence of the horizontal distance
21、of tremor focal point on the increase in methane concentration in driven longwalls and roadheads. The greatest number of mine tremors which caused increase in methane concentration in the working faces were those, with focal points located near the mine face. The range of influence of the mine tremo
22、r focal point location on the increase in methane concentration in longwall faces reached about 6070 m before the mine face, and to a large degree was dependant on mining and geological conditions (downthrows, edges). The most significant value of the increase in methane concentration was caused by
23、tremors, focal points of which were situated up to 30 m from the working face 5,6. However, the range of influence of tremors located in goafs on increase in methane concentration in working faces reached 30 m outside that distance the influence of the tremor disappeared totally. The influence of th
24、e horizontal distance of tremor focus from the total length of faces on increase in methane concentration in the longwall faces is shown in Figure 2. In the headings the range of the tremor influence on increase in methane concentration reached up to 60 m in the radius from the heading face or headi
25、ng wall. It should be also mentioned that determining the exact place of the tremor focal point is extremely difficult because focal points are also of different size. For example, according to the research the tremor with energy of E=106J has the focal point of range 150200 m, so it is comparable w
26、ith the length of longwall face 1. Example 1 In the seam 703, in the face M-6, mine tremor with energy of 1,4x106J took place. It happened at 9.27pm on 24.11.97. The focal point was located 170m before the longwall front and 30m from the face heading. The tremor of so big energy caused small increase in methane 00.10.20.30.40.50.60.70.80.9Average increase in methane concentration %Energy of tremor JII CategoryIV Category102 103 104 105 106
