Wave Propagation in Isotropic Media with Two Orthogonal Fracture Sets

Orthogonal intersecting fracture sets form fracture networks that affect the hydraulic and mechanical integrity of a rock mass. Interpretation of elastic waves propagated through orthogonal fracture networks is complicated by guided modes that propagate along and between fractures, by multiple inter...

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Bibliographic Details
Published in:Rock mechanics and rock engineering 2016-10, Vol.49 (10), p.4033-4048
Main Authors: Shao, S., Pyrak-Nolte, L. J.
Format: Article
Language:English
Subjects:
Civil Engineering
Crack propagation
Earth and Environmental Science
Earth Sciences
Elastic waves
Engineering
Fracture mechanics
Geology
Geophysics
Geophysics/Geodesy
Intersections
Isotropic media
Networks
Original Paper
Propagation
Rock
Rocks
Stiffness
Wave propagation
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Summary:Orthogonal intersecting fracture sets form fracture networks that affect the hydraulic and mechanical integrity of a rock mass. Interpretation of elastic waves propagated through orthogonal fracture networks is complicated by guided modes that propagate along and between fractures, by multiple internal reflections, as well as by scattering from fracture intersections. The existence of some or all of these potentially overlapping modes depends on local stress fields that can preferentially close or open either one or both sets of fractures. In this study, an acoustic wave front imaging system was used to examine the effect of bi-axial loading conditions on acoustic wave propagation in isotropic media containing two orthogonal fracture sets. From the experimental data, orthogonal intersecting fracture sets support guided waves that depend on fracture spacing and fracture-specific stiffnesses. In addition, fracture intersections have stronger effects on propagating wave fronts than merely the superposition of the effects of two independent fractures because of energy partitioning among transmitted/reflected waves, scattered waves and guided modes. Interpretation of the properties of fractures or fracture sets from seismic measurements must consider non-uniform fracture stiffnesses within and among fracture sets, as well as considering the striking effects of fracture intersections on wave propagation.
ISSN:0723-2632
1434-453X
DOI:10.1007/s00603-016-1084-z