外文翻译-井下应用综放的突出危险指数.doc

1、Application of outburst risk indices in the underground coal mines by sublevel cavingJavier Toran o a,n, Susana Torno a, Eliseo Alvarez b, Pedro Riesgo a School of Mines, Oviedo University, Asturias, SpainMining Engineer of Hullera Vasco Leonesa S.A., Santa Lucia, Leon, Spain articleInfoArticle hist

2、ory:Received 7 January 2011.Received in revised form 30 December 2011Accepted 8 January 2012.Available online 20 January 2012 Keywords: Outburst Methane Heading face Desorption rate Drill cutting Gas pressureAbstract The underground coal mines of Hullera Vasco Leonesa SA (HVL) have exhibited sudden

3、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 a coalbed located 17 m below a roadway in which the shortwall and sublevel caving method

4、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 thelaboratories of HVL.The aim of this study is to analyse the advantages and drawbacks of the chosen

5、indices, theirrelationship 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 different borehole degasication patterns and water injection in those boreholes. It is concluded

6、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 totally extrapolated to other underground coal mines.Introduction HVL Company located in the provin

7、ce of Leon in the North of Spain, 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.

8、75% of Sulfur, 10.41% of volatiles, a caloric value of 7455 Kcal/kg and a density of 1.45 kg/m3Stratigraphically, the coal basin is divided into six well-dened formations. The whole group is about 1500 m thick, formed about 300 million years ago. Pastora Formation shows the best economic prospects a

9、nd it provides the totality 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

10、in underground coal mines worldwide,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 classied into two groups: those originated in the caved zone as a result only of the gas pre

11、ssure action, called Gas 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 be

12、tween them. The area marked 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 ca

13、ving. 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 Gas Spallings or Blows are more frequent than outbursts and they produce greater amount of ejected gas, ve blows in years 2009 and 2010 with values ranging between 3000 and 16,

14、000 m3 of emitted gas have 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 rst stage in which the disintegration and projection of coal a

15、re produced, and a second stage, in which high emissions of methane occur 7,8.The outbursts which happened in HVL can be classied as medium type, with approximately 300 t of coal ejected and about 1000 m3 ofemitted gas.Here outbursts are usually produced shortly (some minutes) after having nished the mining works and the ejected coal comes from the upper part of the heading which is being driven; thatcoal lies on the oor of the heading in an elongated position as a consequence of its pneumatic transport with the formation of canals 9. formation of canals。In Fig. 2a, there is a schemat