Guided acoustic waves at the intersection of interfaces and surfaces

Pupyrev, Pavel D.; Nedospasov, Ilya; Mayer, Andreas

doi:10.1016/j.ultras.2019.03.002

Cited by 6 publications

(1 citation statement)

References 28 publications

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“…Within this framework, we can group previous research into short wavelength ( λ / a < 10) and long wavelength ( λ / a > 10) propagation studies. Short‐wavelength propagation studies have explored the angle of incidence (Gu et al., 1996), multiple parallel fractures (Pyrak‐Nolte et al., 1990a; Schoenberg, 1983; Shao & Pyrak‐Nolte, 2016), fracture intersection waves (Abell et al., 2017; Pupyrev et al., 2019), and fluid‐filled fractures (Barbosa et al., 2016; Pyrak‐Nolte et al., 1990b). Associated analyses often assume continuous stress but discontinuous displacements across the fracture (Schoenberg, 1980).…”

Section: Introductionmentioning

confidence: 99%

Long‐Wavelength Propagation in Fractured Rock Masses (3D Stress Field)

2022

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Fractured rocks affect a wide range of natural processes and engineering systems. In most cases, the seismic characterization of fractured rock masses in the field involves wavelengths much longer than the fracture spacing; reproducing this condition in the laboratory is experimentally challenging. This experimental investigation explores the effect of fracture rock fabric and the 3D stress field on P wave propagation in the long‐wavelength regime using a large‐scale true triaxial device. P wave velocities increase with stress in the propagation direction and follow a power law of the form Vp = α(σ’/kPa)β; analyses and experimental results show that stress‐sensitive fracture stiffness and fracture density define the α‐factor and β‐exponent; conversely, long‐wavelength velocity versus stress data can be analyzed to identify the stress‐dependent fracture stiffness. P wave velocities exhibit hysteretic behavior caused by inelastic fracture deformation and fabric changes. During deviatoric loading, the P wave velocity decreases in the two constant‐stress directions due to the development of internal force chains and the ensuing three‐dimensional deformation. Following a load increment, time‐dependent contact deformations result in P wave velocity changes during the first several hours for the tested carbonate rocks; the asymptotic change in velocity is more pronounced for higher stress changes and stress levels. The fracture network geometry that defines the rock fabric acts as a low‐pass filter to wave propagation, so that wavelengths must be longer than two times the fracture spacing to propagate (Brillouin dispersion); the long‐wavelength velocity and the fracture spacing determine the cutoff frequency. Fabric anisotropy contributes to anisotropic low‐pass filtering effects in the rock mass.

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