Inversion of ultrasonic wave velocity measurements to obtain the microcrack orientation distribution function in rocks

✍ Scribed by C.M. Sayers

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 477 KB
• Volume: 35
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(90)90157-c

✦ Synopsis

The elastic wave velocities in rock are reduced significantly by the presence. of microcracks. As a result of the stress history of the rock these microcracks frequently exhibit some degree of alignment. The rock therefore displays an elastic anisotropy determined by the shape and content of the cracks and by the crack orientation distribution function. The coefficients W',,,," of a series expansion of this function in generalized spherical harmonics can be obtained to order I = 4 from the angular variation of the elastic wave velocities. This allows construction of microfracture pole figures, which may be compared with those obtained by petrofabric examination. Since the anisotropy in strength properties originates from the preferred orientation of microstructural defects, the prediction of the microfracture orientation distribution will have an important application in the field of rock fracture.