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1、翻译部分英文原文AbstractIn this paper, the experimental results of a 45-kW and 15-t roadheader excavating a gallery with two different types of rock at the face using two different cutting heads are shown. It is proved that the roadheader works properly with both cutting heads. In comparison with other resu
2、lts in the literature, the principal parameters, i.e. specific energy, cutting rate and tool wear, are at a level that can be considered satisfactory taking into account the low power of the roadheader. On the other hand, the influence of the number of picks, which is the main difference between the
3、 two cutting heads, on the operational parameters is shown.2003 Elsevier Science Ltd. All rights reserved.Keywords: Roadheaders; Cutting head design; Specific cutting energy; Cutting rate; Tool wear1. Introduction: experience in using of roadheaders in a mineThe coal basin in the NW of Spain (Areces
4、et al.,1994) forms a syncline in which the coal seams are moderately inclined (30358) at the NW fold axis and almost vertical (70908) at the SE fold axis. Carboniferous material occurs under a flat Permian overburden,150 m thick.The use of roadheaders in this mine was a consequence of mechanisation
5、of the work. Coal mining by the long-wall method with powered roof supports makes rapid advance of the access roads necessary. On the other hand, the two alternatives for mining very thick coal seams, i.e. room-and-pillar in flat seams and sublevel caving in vertical seams, also makes the use of roa
6、dheader driving galleries in the coal seams necessary Several types of roadheaders are used in the mine for these different works:a. One roadheader (Fig. 1) of 60 t in weight, with a 250-kW ripping cutting head, especially designed for this type of mine in the context of research project (Anon., 199
7、1; Torano et al., 1992; Torano, 1994) with the objective of driving galleries of 10-m cross- 2 sections in coal seams of 1.01.5 m in thickness (with approx. 50% of the section in hard rock of uniaxial compressive strength up to sc120 MPa);b. Two roadheaders (Fig. 2) of 24 t in weight, with a 110-kW
8、ripping cutting head mainly used in driving galleries with medium hard rock (c60 MPa) or in croom-and-pillar mining;c. Two roadheaders (Fig. 3) of 12.5 t in weight with a milling cutting head of 45 kW, only used in advancing of galleries in coal (soft rock); the conveyor type means the roadheader ha
9、s a 2.8-m width and because of this it can only be used for advancing galleries in coal seams of 3.0 m in thickness (mainly in the mining method termed sublevel caving); andd. One roadheader (Fig. 4) of 15.5 t in weight with a 45-kW milling-type cutting head, developed with this narrow design especi
10、ally for this mine (Torano et al., 1997) for its application in driving galleries in 2.0-m-thick coal seams (minimum 1.70 m) in which previous roadheaders could not be used.The study described here was carried out in the context of this project. During the advance of galleries in 2.0-m-thick coal se
11、ams, it was sometimes necessary to excavate the rock of the seam walls, the strength of which was almost over the limit of the cutting capacity of the roadheader. It was decided to investigate if, under these conditions, the operation or cutting parameters were acceptable using two different cutting
12、 heads in the test.2. Test description2.1. Test objectivesThe aim was to determine the possibility of driving these galleries by means of a 45-kW roadheader, comparing two different cutting heads excavating the same type of rock in similar operating cycles. The main difference between the two cuttin
13、g heads was the number of picks: the first cutting head had 36 picks, while the new one had only 24 (Fig. 5).Because of the lower number of cutting tools in contact with the rock, the torque transmitted by the motor was trans formed to a larger tangential force in the pick, which allows higher -stre
14、ngth rock to be cut. Stress concentration is the major factor in rock fragmentation. The parameters to measure (according to classic studies on this theme; Fowell and McFeat-Smith, 1976;Gehring, 1989) are the cutting rate (volume of rock excavated per time unit in m3/s), specific energy (ener- 3 gy
15、necessary to excavate a unit of volume in MJ/m3 ) 3 and the tool wear or specific pick consumption (picks or pick mass lost excavating a unit of volume of rock in picks/m3 or g/m3 ). All parameters were measured 3 3 when the roadheader was excavating coal and rock, as well as when it was performing
16、other parts of the cycle.2.2. Description of the excavated faceThe coal seam mined by the sublevel caving method was vertical and its average thicknesswas2.0 m. With the aim of carrying out the test in the worst conditions, the test zone used was in an area with a seam thickness of less than 2.0 m. A three-segment steel set support was used, the gallery being of 2.50 m in width at the low part and 3.0 m high. In Fig. 6 sketches of the
