1、外文原文：http:/ 中文 4757 字 翻译部分 英文原文 Abstract In 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
2、 both cutting heads. In comparison with other results 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
3、of picks, which is the main difference between the 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 wear 1. Introduction: experience in using of roadheade
4、rs in a mine The coal basin in the NW of Spain (Areceset 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 roadhe
5、aders in this mine was a consequence of mechanisation 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 sublev
6、el caving in vertical seams, also makes the use of roadheader 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
7、 of mine in the context of research project (Anon., 1991； 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. Tw
8、o roadheaders (Fig. 2) of 24 t in weight, with a 110-kW 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 co
9、al (soft rock)； the conveyor type means the roadheader has 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)； and d. One roadheader (Fig. 4) of 15.5 t in weight with a 45-kW milling-t
10、ype cutting head, developed with this narrow design especially 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 thi
11、s project. During the advance of galleries in 2.0-m-thick coal seams, 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
12、or cutting parameters were acceptable using two different cutting heads in the test. 2. Test description 2.1. Test objectives The 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
13、similar operating cycles. The main difference between the two cutting 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
14、 to a larger tangential force in the pick, which allows higher -strength 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
15、 rock excavated per time unit in m3/s), specific energy (ener- 3 gy 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 other parts of the cycle.
