外文翻译-块度大小对煤的抗压强度的影响.doc

1、翻译部分英文原文Effect of size on the compressive strength of coalH. MoomivandFaculty of Engineering, University of Urmia, IranAbstract: The compressive strength of coal depends on the distribution, type and condition of discontinuities. In the smaller specimen, the probability of finding larger discontinui

2、ties is smaller and the compressive strength is thus higher. All groups of laboratory and in situ test results were analyzed by a DataFit computer program separately. It was shown that the effect of size on the compressive strength of 10 different groups of coal is not the same. Compressive strength

3、 of different groups of coal specimens had a high scatter for the same size and strength-size relationship bad high deviation when all groups of results were mixed. Compressive strength of specimens was divided by the compressive strength of a specimen having a size equal to d (in this analysis 50.8

4、mm) in any group of test results. Consequently the dimension of strength in all series of tests was omitted and the relationship between the ratio of compressive strengths and size for all groups of results was determined. From extrapolating laboratory and in situ test results, the relationship betw

5、een compressive strength and size of all cubic coal specimens was derived.Key words: Compressive strength; Coal specimens; Size1. IntroductionThe discontinuities of various sizes are present in rock mass. The compressive strength, as a function of discontinuities, increases with a decrease in size o

6、f rock specimens, A new definition for size effect on the compressive strength has been given as it can represent the phenomenon. Most of the experimental results available are for coal and are concerned especially with the compressive strength of cubes of various edge dimensions. The effect of size

7、 on the compressive strength of coal has been investigated by conducting tests both in the laboratory and in situ. The effect of size on the compressive strength of all laboratory and in situ test results of cubic coal specimens has been analysed using DataFit computer program (1992). From extrapola

8、ting laboratory and in situ test results, the relationship between compressive strength and size of all cubic coal specimens has been derived.2. Effect of size on the compressive strength of coal specimens2.1 Laboratory testsCoal contains various discontinuities such as cracks, pores, etc. The compr

9、essive strength of rock (coal) depends on the distribution, type and condition of discontinuities. In the smaller specimen, the probability of finding larger discontinuities is smaller and the compressive strength is thus higher. The effect of size on the compressive strength of different types of r

10、ock specimens is not the same (Moomivand, 1993).The compressive strength increases with a decrease in size of coal specimens (Daniels & Moore 1907, Rice 1929, Lawall & Holland 1937, Steart 1954, Gaddy 1956, Evans et al. 1961), Gaddy (1956) tested the compressive strength of a large number of cubes f

11、rom 5 different seams including Pittsburgh, Ctintwood, Pocahontas No.4, Harlan and Marker having edge dimension from 0.051m to 1.626m and he proposed the following relationship between compressive strength and specimen size: (1)Where = compressive strength of cubical coal specimen having edge dimens

12、ion D; and K = a coefficient depending upon the chemical and physical properties of the coal.2.2 In situ testsIn the cutting and curing of a rock specimen for laboratory testing, not only are cracks, joints and weaknesses reduced from a large size (rock mass) to a small laboratory size but also with

13、 the transporting of specimens from mines to the laboratory and with the cutting of samples to a small size, the environment changes which can affect strength. When the specimens are dried at a constant temperature over a period of a few weeks, a smaller specimen may be drier than a larger one. Ther

14、efore, the moisture content of different size specimens cannot be constant. Also, the moisture content of a larger specimen will be less homogeneous from its centre to its surface in comparison to a smaller specimen.Bieniawski (1968) conducted in situ compression tests of sixty cubical coal specimen

15、s having edge dimension from 0.019m to 2.012m underground. He classified the tests into three groups, a small size (up to 0.076m), a medium size (up to 0.457m) and a large size (up to 2.012 m). He showed that compressive strength decreases with increasing specimen size and becomes constant when it r

16、eaches the critical specimen size (about 1.524m), and suggested three different equations for different sizes of specimen as follows:(a) Initial constant strength relationship (= constant):For this case a specific value was not given for the edge dimension and other , investigators have found significant variations in strength with sizes in this region (Evans 1970). Different methods were employed to prepare the