1、翻译部分英语原文Application of outburst risk indices in the underground coal mines by sublevel cavingJavier Torano a,n, Susana Torno a, Eliseo Alvarez b, Pedro Riesgo a(1)School of Mines, Oviedo University, Asturias, Spain(2)Mining Engineer of Hullera Vasco Leonesa S.A., Santa Lucia, Leon, Spaina b s t r a
2、c tThe underground coal mines of Hullera Vasco Leonesa SA (HVL) have exhibited sudden emissions of methane called “blows” and outbursts. A research study has been conducted in order to analyse those risk indices with a greater impact on the prediction and control of outbursts in a heading driven in
3、a coalbed located 17 m below a roadway in which the shortwall and sublevel caving method is being employed. Extensive measurement 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 laborator
4、ies of HVL.The aim of this study is to analyse the advantages and drawbacks of the chosen indices, their relationship with operating parameters such as distance between the heading face and the shortwall face, height difference between both levels, heading face and roadway, optimization of the diffe
5、rent borehole degasification patterns and water injection in those boreholes. It is concluded that a simple methodology to predict 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 total
6、ly extrapolated to other underground coal mines.Crown Copyright & 2012 Published by Elsevier Ltd. All rights reserved.1. IntroductionHVL Company located in the province of Leon in the North of Spain, is an underground coal mine with three shafts connected between them. The annual coal production is
7、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 volatiles, a calorific value of 7455 Kcal/kg and a density of 1.45 kg/m3.Stratigraphically, the coal basin is
8、 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 eco-nomic prospects and it provides the totality of the present coal production. The Pastora coalbed varies in thickness from 20 to 25 m, its dip is
9、between 401 and 701 and the methane concentra-tion 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 worldwide, sometimes with fatal consequences for workers 1 3. In under-ground coal mines using suble
10、vel caving combined with shortwall, as it is in HVL, sudden methane emissions can be classified into twogroups: those originated in the caved zone as a result only of the gas pressure action, called Gas spallings or Blows and Outbursts generated in roadways driven in coalbeds where gas pressure ener
11、gy 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 marked with an (A) is the place where Gas spallings or Blows have taken place and that marked with(B
12、) 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 coalbed has a thickness of 9 m, a dip of 701 and its roof and footwall are made up of shales.Although
13、 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 m3 of emitted gas have taken place. These emissions were not so instant, and the problems associated with them were s
14、olved 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 second stage, in which high emissions of methane occur 7, 8. The outbursts which happened in HVL can
15、 be classified as medium type, with approximately 300 t of coal ejected and about 1000 m3 of emitted gas.J. Torano et al. / International Journal of Rock Mechanics & Mining Sciences 50 (2012) 9410195Here outbursts are usually produced shortly (some minutes) after having finished the mining works and
16、 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 of canals 9.In Fig. 2a, there is a schematic representation of a panel mined by shortwall and sublevel caving between two levels with a detailed view of the broken coal a
