1、翻译部分翻译部分 外文原文：Application of outburst risk indices in the underground coal mines by sublevel cavingJavier Toranoa,n, Susana Tornoa, Eliseo Alvarezb, Pedro RiesgoaABSTRACT:The underground coal mines of Hullera Vasco Leonesa SA (HVL) have exhibited sudden emissions of methane called blows and outburst
2、s. A research study has been conducted in order to analyse those risk indices with a greater impact on the predi- ction and control of outbursts in a heading driven in a coalbed located 17 m below a road- way in which the shortwall and sublevel caving method is being employed. Extensive mea- suremen
3、t programmes have been carried out in an operating coal mine, both in the heading face and in the coal above it. Coal samples have been analysed and tested in the laboratories of HVL. The aim of this study is to analyse the advantages and drawbacks of the chosen indices, their relationship with oper
4、ating parameters such as distance between the heading face and the shortwall face, height difference between both levels, heading face and roadway, optimization of the different borehole degasification patterns and water injection in those boreholes. It is concluded that a simple methodology to pred
5、ict and control sudden methane outbursts has been developed and put into practice in HVL. This methodology is based on the mentioned indices and it can be partially or totally extrapolated to other underground coal mines.1.IntroductionHVL Company located in the province of Leon in the North of Spain
6、, is an underground coal mine with three shafts connected between them. The annual coal production is 2 million tons and the proved exploitable coal reserves at the end of 2010 are 45 million tons. The average coal properties of the mined coalbed are 12.39% of Ash, 0.75% of Sulfur, 10.41% of volatil
7、es, a calorific value of 7455 Kcal/kg and a density of 1.45 kg/m3.Stratigraphically, the coal basin is divided into six well-defined formations. The whole group is about 1500 m thick, formed about 300 million years ago. Pastora Formation shows the best economic prospects and it provides the totality
8、 of the present coal production. The Pastora coalbed varies in thickness from 20 to 25 m, its dip is between 401 and 701 and the methane concentration varies between 7 and 10 m3/t of coal.Numerous violent sudden emissions of coal, rock and methane(outbursts) have occurred in underground coal mines w
9、orldwide, sometimes with fatal consequences for workers 13. In underground coal mines using sublevel caving combined with shortwall, as it is in HVL, sudden methane emissions can be classified into two groups: those originated in the caved zone as a result only of the gas pressure action, called Gas
10、 spallings or Blows and Outbursts generated in roadways driven in coalbeds where gas pressure energy is added to the energy from coal and rock stress 4,5.Fig. 1 shows the main ventilation network of the mine, which is accessible by means of three vertical shafts connected between them. The area mark
11、ed with an (A) is the place where Gas spallings or Blows have taken place and that marked with (B) is the place where outbursts have occurred. While in the area (A) the mining method is sublevel caving, in the area (B) the mining method is shortwall combined with sublevel caving. In area (B) the coa
12、lbed has a thickness of 9 m, a dip of 701 and its roof and footwall are made up of shales.Although Gas Spallings or Blows are more frequent than outbursts and they produce greater amount of ejected gas, five blows in years 2009 and 2010 with values ranging between 3000 and 16,000 m3of emitted gas ha
13、ve taken place. These emissions were not so instant, and the problems associated with them were solved with an appropriate main and auxiliary ventilation 6.Outbursts are violent phenomena of short duration, with a first stage in which the disintegration and projection of coal are produced, and a sec
14、ond stage, in which high emissions of methane occur 7,8. The outbursts which happened in HVL can be classified as medium type, with approximately 300 t of coal ejected and about 1000 m3 of emitted gas.Here outbursts are usually produced shortly (some minutes) after having finished the mining works a
15、nd the ejected coal comes from the upper part of the heading which is being driven; that coal lies on the floor of the heading in an elongated position as a consequence of its pneumatic transport with the formation ofcanals 9.In Fig. 2a, there is a schematic representation of a panel mined by shortw
16、all and sublevel caving between two levels with a detailed view of the broken coal and shield supports. Between the roadway at level 865 (a) and the roadway at level 740 (b), an incline with a dip of 381 (c) is driven. From these shaft eight crosscuts (d) pass through the coalbed, and from the intersection two roadways of 250 m each are driven to the East (e) and (f) and West (g) and (h) in the coalbed. The coal
