TITLE:
Assessments of Elastic Anisotropy of Banded Amphibolite as a Function of Cleavage Orientation Using S- and P-Wave Velocity
AUTHORS:
Ali Esamaldeen, Guang Wu, Mohamed Nuha
KEYWORDS:
Anisotropic, Elastic Modulus, Foliation, P- and S-Waves, Ultrasonic Pulse
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.3 No.5,
July
17,
2015
ABSTRACT:
As most rocks are of an anisotropic nature,
the measurement elastic modulus of anistropic rocks is of general interest.
Nevertheless, uniaxial compression test is common method to measure the dynamic
elastic constants of anisotropic rocks; the use of ultrasonic pulse test is
attractive, because the test is non-destructive and easy to apply. This study aimed
to demonstrate the influence of orientation of foliation planes of banded
amphibolite rocks on the compressional (Vp), shear wave (Vs) velocities
propagating and elastic modules using ultrasonic pulse test. The result showed
that the planes of foliation have a major effect on the wave velocity, where
the Vp and Vs were taken parallel to the foliation plane show higher values
than those obtained in the other directions (β = 30。, 60。 and 90。). The
preliminary conclusions are developed concerning that the elastic modulus is
vary continuously as a function of cleavage orientation with respect to the direction
of wave propagations, where Poisson’s ratio having the smallest relative
change. The highest values of Young’s modulus and shear modulus are observed
for foliation dip angles of 0? and the lowest values are for foliation dip
angles of 90。. This indicates that the observed intrinsic anisotropy and the
close relations of the directional dependent seismic anisotropy to the
foliation planes are mainly a result of crystallographic preferred orientation
of major minerals (e.g. horn- blende and elongated quarts grains).