1、翻 译 部 分英文原文A new coal pillars design method in order to enhance safety of the retreat mining in room and pillars minesE.Ghasemi*,K.ShahriarDepartment of Mining of and Metallurgical Engineering,Amirkabir University of Technology,Tehran,IranAbstract:Most of the proposed methods of coal pillar design d
2、etermine pillar dimensions using pillar estimation only through the tributary area theory.Designing pillar based on these methods is not appropriate in room and pillar mines with pillar recovery because retreat mining and gob creation generate abutment loads.Neglecting abutment loads in design stage
3、 may lead to pillar failure and destructive effects during retreat mining.Thus proper pillar design has a remarkable effect on mining effect on mining safety.In this paper,a step-bu-step method is presented to design pillars with square shape in room and pillar mines with regard to existing pillars
4、in the active mining zone(AMZ) and estimating abutment loads according to experiment-method. This method has been applied to determine optimum pillar dimensions in the main panel of Tabas Cental Mine(TCM),located in the mid-eastern part of Iran.Obtained results show the abutment loads account for 27
5、%of the total loads applied on pillars in AMZ in this panel.Pillar width,based on this method, is also obtained 11.6m.Key words: Pillar design;Room and pillar;Retreat mining; Active mining zone;Abutment loads1. IntroductionIn underground coal mining ,room and pillar is the method of working preferab
6、le for flat,tabular deposits in thin seams,where rooms of entries are driven in the solid coal to form pillars in the development panels(Hustrulid,1982;Hartman,1978).Pillars o f coal are left behind to support the roof and prevent its collapse,thereby allowing miners to extract coal between them and
7、 to travel safely. In some cases, the pillars are removed partly or fully in a later operation, known as retreat mining(also known as secondary mining or pillar recovery operation). Coal mine pillar design has been the subject of sustained and intensive research in the major coal producing countries
8、 in the word. Pillar design and stability are two of the most complicated and extensive problems in mining related to rock mechanics and ground control subjects. Although these problems have been investigated for a long time, to date only a limited understanding of the subject has been gained. The s
9、ubject of pillar design in the US goes back nearly a centry. Prior to this the dimensions of pillar were largely determined rules of thumb such research as there was tended to be isolated and sporadic. But nowadays, various pillar design formulas are developed, based upon laboratory testing, full-sc
10、ale pillar testing, and back-analysis of failed and successful case histories. In 1980, field studies conducted by the US Bureau of Mines has developed the classic pillar design methodology. It consisted of three steps(Mark,2006): 1.Estimating the pillar load; 2.Estimating the pillar strength ,and 3
11、.Calculating the pillar safety factor.Th average pillar, in regular layouts of pillars can be estimated by tributary-area theory, each individual pillar is assumed to carry the weight of the overburden immediately above it. In the other words, a pillar uniformly supports the weight of rock overlying
12、 the pillar and one-half the width of rooms and entries on each side of the pillar(Peng,1978).Pillar strength can be defined as the maximum resistance of a pillar to axial compression(Brady and Brown,1993). Empirical evidence suggests that pillar strength is related to both its volume and its shape(
13、Salamon and Munro,1967;Brady and Brown,1993).Numerous formulas have been developed that can be used to estimate the strength of pillars in coal mines, which Table 1 shows the most applicable of them. Each of these formulas estimates the to pillar strength in terms of two various; width to height rat
14、ion and in situ coal strength.Bieniawski(1981) represented very good classic approach to pillar design. He at fist described the issues involved in pillar design, and advantages and shortcomings of the available methods and then represented a logical, step-by-step approach to determine the coal pill
15、ars dimensions in room and pillar mines. Table 1Most applicable of empirical strength formula for coal pillars.Pillar strength formulas(MPa)ReferencePillar cross-sectionRemarksSalamon and Munro (1967)SquareBieniawski (1968)SquareMadden(1991)SquareMark and Chase (1997)SquareNowadays in most of the ro
16、om and pillar mines in order to increase recovery and productivity,remanent pillars in panels are recovered by retreat mining. Since, the above mentioned methods are not appropriate for pillar design because these methods neglect the abutment loads due to retreat mining and creation of a mined out gob. Abutment loads affect on the pillar in the adjacent of pillar line and a load more than the one e
