1、英文原文Fractal approach to determine rock mass strength and deformationM.N. Bagde,A.K. Raina, P.B. Choudhury &A. SinhaABSTRACT: Rock mass strength and deformation estimation is necessary for the design of rock excavation and stability. Various empirical approaches are available for a reasonable estimat
2、e of these parameters. To eliminate randomness and to incorporate more preciseness and reliability in the estimate, the fractal approach was introduced in the present study. The fractal dimensions were estimated from the block size distribution obtained from the images of fragmented muck pile and th
3、e in-situ rock mass. In total 10 broad types of rock formations were investigated at 22 different field sites. The rock mass strength and deformation were estimated using popular empirical approaches.The average rock mass strength and deformation showed a relationship with the change in fractal dime
4、nsions from in-situ to fragmented ones subjected to unit specific charge i.e. quantity of explosives used per unit volume of rock mass. A new estimation technique towards rock mass strength and modulus using fractal approach is presented in this paper.Subject:Analysis techniques and design methodsKe
5、ywords:Rock mass, rock mass classification, blasting, mining1 INTRODUCTIONRock tests constitute one of the bases for theoretical and numerical analysis and design, and are considered important support for studying rock mechanics and engineering. The key to the reliability of the empirical and numeri
6、cal analyses lies in the rational assessment of the rock mass properties. It is difficult to determine accurately the relevant properties used in the analyses, since, the rock mass is characterized by the discontinuities in the form of joints, fractures, and other micro-fissures. The block size, whi
7、ch is defined by discon- tinuity spacing, the number of joint sets and the persistence of the discontinuities,is an important indicator of the degree of fracturing of a rock mass.The block size is included implicitly in all rock mass classification systems employed for analysis and design of surface
8、 and underground mining structures. In-situ block size distributions provide a better means to describe the structural complexity of a rock mass.Rock mass strength and deformation modulus have got several applications in rock excavation engineering,especially for design of underground structures. Ma
9、ny empirical approaches are presently available for their assessment. The data collection procedure for this purpose requires considerable field study and laboratory work. Also it was felt many times that the end result is person specific.Since,there is apossibility of losing preciseness and reliabi
10、lity of the conclusions drawn on the basis of the hard earned data.Fractal geometry is being applied to rock mechanics since its initiation in the early 1980s. The fractal geometry of rock discontinuity patterns appears to be potentially useful for many applications concerning the rock mass behavior
11、. The fractal number provides information on the degree of nonuniformity in the block sizes present in in-situ or fragmented rock mass. For more basic literature on the subject kindly refer to Mandelbrot (1967, 1983); Turcotte (1986, 1992) and for brief review related to its application to rock mech
12、anics refer to Bagde et al. (2002). To eliminate randomness and to incorporate more preciseness and reliability in the estimation of rock mass strength and modulus, the fractal approach wasintroduced in the present study.2 FIELDAND LABORATORY INVESTIGATIONSA total of 22 various field sites scattered
13、 throughout India were covered in the presentstudy.The various rock formations covered include sandstone, limestone, granite, manganese, basalt, sillimanite, flourite, iron ore (hematite), laterite and bauxite etc.The core samples were collected from various blast sites and to determine the uniaxial
14、 compressive strength (UCS) and modulus of elasticity (E) in the laboratory. The digital Schmidt hammer was used to obtain the in-situ strength of the rock mass. The Rock Mass Rating (RMR) of Bieniawski, (1978) was used for each blast site rock formation to classify the rock mass.Trials blasts were
15、conducted in each of the 22 sites. For each site, images of the rock mass (pre-blast) and the fragmented muck piles (post-blast) were taken and subjected to digital image analysis for obtaining the block size (width) distribution.2.1 Estimation of fractal dimensionsIn the present study the digital i
16、mage analysis of in-situ and blasted fragments were carried out using WipFrag Ver 2.3 (Make WipWare Inc., Canada) software. Nearly 15 numbers of pre- and post- blast images were analyzed in each case.The log of the block size data were clustered in six equal intervals between the minimum (not less than 0.01cm) and maxi mumsize.The cumulative frequency distributions of different clusters were obtained from those data. The trend line of the log of the cumulati
