SYMPOSIA PAPER Published: 01 January 1979

and of Westerly Granite—Effects of Thickness and In-Plane Dimensions


An investigation is described in which tensile properties, fracture toughness, and critical J-integral are measured for Westerly granite, a rock that is used widely in rock mechanics studies. This was primarily a parameter sensitivity study in which the effects of specimen dimensions and testing techniques were assessed. It is hoped that this study will aid in establishing tentative standards and guidelines for fracture toughness testing of rock as well as indicate the feasibility of using a J-integral fracture criterion for this material.

ASTM standard specimen configurations of the compact and bend types were tested with compact specimens ranging in width from W = 25.4 mm to W = 406.4 mm (0.5T to 8T) and with thickness ranging from 13 to 100 mm. A series of 4T compact specimens were tested to assess the effects of thickness and fatigue precracking.

Techniques are described that enable several values of KIc, a complete J versus crack growth curve, and a JIc value to be obtained from each sample. Direct-pull tension tests on shaped specimens of Westerly granite are described which indicate a high degree of nonlinear, inelastic behavior. This fact raises questions about the use of linear elastic fracture mechanics, LEFM, but the JIc data presented appear to validate the KIc measurements.

Author Information

Schmidt, RA
Sandia Laboratories, Albuquerque, N. Mex.
Lutz, TJ
Sandia Laboratories, Albuquerque, N. Mex.
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Developed by Committee: E08
Pages: 166–182
DOI: 10.1520/STP36635S
ISBN-EB: 978-0-8031-4747-8
ISBN-13: 978-0-8031-0365-8