Abstract
The present study concentrates on water induced strength reduction and variation of the failure mode in indirect (Brazilian) tension tests of several igneous rock materials under three moisture cases of oven-dry, air-dry and fully saturated states. In this respect, two andesite and three tuff materials which contain no visible flaws were subjected to indirect tensile strength tests using the Brazilian disc method. Once the tension tests were carried out, photographs of the broken samples were taken to investigate the changes in the failure mode. As a result, it was found that tensile strengths of the samples were highly reduced with the presence of the water and the natural humidity. Additionally, it has been deduced that the failure mode of the samples mainly shifts to central fracturing with the presence of natural moisture and saturation. Although the central crack is the ideal type for the theory of Brazilian tensile strength determination, indefinite contact properties like contact angle and frictions are some notable issues to make only considering failure shapes for the validity of the test results misleading. Keywords: Failure mode; Igneous Rocks; Strength reduction; Tensile strength DOI 10.35180/gse-2020-0031
Highlights
Mechanical properties of rocks are sensitive to the testing and environmental conditions, such as loading rate, platen type, moisture content, etc
While most of the studies concentrated on the weakening effect of water on the uniaxial compressive strength, lesser amount of research focused on the strength reduction in tension tests
Even though numerous studies investigated the effect of saturation on the strength reduction, a limited number of the studies concentrated on the variation of the failure type or mode, especially in tension tests
Summary
Mechanical properties of rocks are sensitive to the testing and environmental conditions, such as loading rate, platen type, moisture content, etc. Moisture or water presence in rocks is one of the main factors controlling the strength and failure mode of the rocks, and the effect of the water saturation on the mechanical properties of rocks have been investigated for a long time since the 1940s [1]. While most of the studies concentrated on the weakening effect of water on the uniaxial compressive strength, lesser amount of research focused on the strength reduction in tension tests. Even though numerous studies investigated the effect of saturation on the strength reduction, a limited number of the studies concentrated on the variation of the failure type or mode, especially in tension tests. There is a paucity of the experimental data for tensile strength and failure mode of igneous rocks
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