外文翻译-通过压力拱理论和区域回采率进行煤柱荷载计算.doc

1、翻译部分翻译部分 外文原文：Coal pillar load calculation by pressure arch theory and near field extraction ratio（B.A. Poulsen CSIRO Earth Science and Resource Engineering,P.O.Box 883,KENMORE 4069 Qld,Australia）ABSTRACTA method for calculating the load acting on a pillar of coal in a bord-and-pillar mine is descri

2、bed for the purpose of back analysing pillar failure or assessing the stability of a panel of pillars. The method is applicable to pillars of arbitrary plan shape and accounts for the spatial position of the pillar with respect to the other pillars, un-mined coal, and the network of roadways. Calcul

3、ation of the extraction ratio within the pillars zone of influence defined by the depth dependent load transfer distance accounts for the pillars spatial position in the mine layout. An advantage of this approach is its suitability for computer programming for the automated analysis of hundreds of p

4、illars. In this paper, pillars are analysed by the new method, and by tributary area theory, with the results from the new method comparing favourably to elastic three dimensional numerical analysis. Finally, an example of coal mine pillar failure from the literature that neither could be satisfacto

5、rily back-analysed by the traditional factor of safety approach nor by two-dimensional numerical modelling is considered. With the proposed, approach 42 of the 54 pillars in the observed failed pillar region are predicted to have a safety factor below the recommended value for long term stability an

6、d of these, three pillars are predicted to have an FoS of 1.18. With tributary area theory every pillar, including all those outside the failed pillar region, is predicted to have an FoS less than 1.2.1 Introduction Pillars in bord-and-pillar mining are formed during the extraction process and remai

7、n to provide stability to the overlying strata1. Conventional theory proposes that local stability is ensured if the pillars strength exceeds the stress placed upon it. The ratio of a pillars estimated strength to the pillars stress is expressed as the factor of safety （FoS）. The nominal FoS for a p

8、illars design is dependent on the consequence of failure of that pillar. It has been proposed 2 that pillars in a coal mine in Australia should have a safety factor of at least 1.6, where it is desirable that they provide stability in the long term and the consequences are not serious if they fail.

9、A safety factor of 2.1 usually applies to situations, where the consequences of failure are severe 3.Pillars designed to a nominal FoS require estimates of both strength and stress. Pillar strength has been a subject of research for many years with analytical formulas and increasingly numerical meth

10、ods 4 used to estimate the strength of a pillar based on its geometric shape, mining height and material strength. In comparison with pillar strength, less research is reported in the literature on estimating a pillars stress 14.Pillar stress may be calculated from the beam theory, numerical methods

11、, or photoelastic techniques, but is most commonly estimated by the tributary area theory 5,6 and is expressed as a multiplier based on the extraction ratio of the in situ vertical stress, which in turn is a function of an average overburden density.With estimates of a pillars strength and the pilla

12、rs stress, it is then possible to estimate an FoS for the pillar, although extrapolating this safety factor to a grouping of pillars or a panel is problematic for a number of reasons: （a） pillars or roadways may not be of uniform dimensions within a panel; （b） pillar load will be dependent on a pill

13、ars proximity to barrier pillars and unmined coal, while tributary theory assumes the pillar is one of an infinite array of pillars; （c） pillar load is also dependent on depth-of-cover, which will vary for a seam with a non-zero dip or due to topographic change; and （d） pillar stability probabilitie

14、s are not independentfailure of any pillar will influence the loading, and hence FoS and stability of adjacent pillars 7.A conceptual theory for pillar loading is based on the pressure arch formed by an excavation in a pre-stressed material. According to this theory stresses arch over an excavation

15、with abutment stresses reducing to pre-mining levels at some distance from the excavation.The present paper introduces the concept of a zone of influence centred on the pillar and based on the load transfer distance to estimate the limit of the pressure arch formed from the creation of the pillar. W

16、ithin this zone of influence, it will be shown that the redistribution of in situ stress is dependent on the extraction ratio, allowing estimation of an average vertical stress, including the pillar stress for the pillar under consideration. A pillars zone of influence and the associated extraction ratio can be determined from the data typically available from a mine CAD system. With this method, it is possible to automate the estimation o