Geometry effects and statistical analysis of mode I fracture in guiting limestone

This paper describes the results of a series of tests conducted to study the mode I fracture toughness of a sedimentary soft rock (Guiting Limestone). Two types of tests were used: centre cracked Brazilian disc specimens subjected to diametral compression and edge cracked semi-circular bend specimens subjected to three-point bend loading. The experimental results showed that there was a noticeable difference between the sets of test data and that the mode I fracture resistance was significantly dependent on the geometry and loading conditions of the test specimen. The difference in fracture resistance between the tested specimens can be related to the effect of the higher order stress term A3. A modified form of the maximum tangential stress which takes into account the effects of A3 was shown to provide a good comparison with the test results. Furthermore, a statistical analysis demonstrated that the modified criterion is also able to predict the statistical parameters for each set of test data.

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