Measurements of the relationship between sonic wave velocities and tensile strength in anisotropic rock

This paper is part of the special publication Developments in petrophysics (eds M.A. Lovell and P.K. Harvey). This work investigates relationships between the mechanical behaviour under tension of a building stone widely use in Italy and the compressional and shear-wave velocities within the stone. The stone investigated is the Antigorio orthogneiss, which is characterized by an orthotropic petrographical anisotropy. This rock was sampled in three orthogonal directions two of which lie in the plane of schistosity, the first parallel and the second perpendicular to the elongated structures in that plane, with the third sampling direction oriented normal to the plane of schistosity. In these directions rock cylinders were cored co-axially to provide hollow cylinders of 14 cm outer diameter together with their inner solid cores of approximately 5 cm diameter. These inner cores were used for ultrasonic wave velocity measurements (V(p) and polarized V(s)) oriented at 90°to the core axis, and conducted at intervals around their circumference so as to obtain wave velocities through the gneiss in different orientations. The hollow cylinders were cut into hoops and tested by the hoop tension test to provide measurements of tensile strength in the same directions as those in which wave velocities had been measured. Thus non- destructive velocity tests and destructive tensile tests were conducted in the same orientations. The paper describes the results so obtained using dry samples.