NATURAL FRACTURE PROFILES, FRACTAL DIMENSION AND JOINT ROUGHNESS COEFFICIENTS

Authors
Citation
Ne. Odling, NATURAL FRACTURE PROFILES, FRACTAL DIMENSION AND JOINT ROUGHNESS COEFFICIENTS, Rock mechanics and rock engineering, 27(3), 1994, pp. 135-153
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary","Engineering, Civil
ISSN journal
0723-2632
Volume
27
Issue
3
Year of publication
1994
Pages
135 - 153
Database
ISI
SICI code
0723-2632(1994)27:3<135:NFPFDA>2.0.ZU;2-8
Abstract
Thirteen natural rock profiles (Barton and Choubey, 1977) are analyzed for their fractal properties. Most of the profiles were found to appr oximate fractal curves but some also showed features of specific wavel engths and amplitudes superimposed. on fractal characteristics. The pr ofiles showed fractal dimensions from 1.1 to 1.5 covering a range of s elf-similar and self-affine curves. The analysis results suggest a neg ative correlation between fractal dimension, D, and amplitude, A. Join t roughness coefficients (JRC) show a positive correlation with amplit ude, A, and a negative correlation with fractal dimension, D. A numeri cal model of fracture closure is used to investigate the effects of di fferent profile characteristics (D, A and sample size) on the nature o f dilation and contact area, using the natural profiles and synthetic fractional Brownian motion profiles. Smooth profiles (low JRC, high D, low A) display many small contact regions whereas rough fractures (hi gh JRC, low D, high A) display few large contact areas. The agreement with published experimental data supports the suggested correlations b etween JRC and the fractal parameters, A and D. It is suggested that o bserved scale effects in JRC and joint dilation can be explained by sm all differential strain discontinuities across fractures, which origin ate at the time of fracture formation.