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Abstract
Water accelerates the deformation and failure of rock and hence deteriorates the stability of rock structures on and under the ground. However, most of the previous studies examined the mechanical properties of rocks in air-dried and water-saturated conditions or the effect of water saturation on compressive strength. In this study, Brazilian tension tests were conducted with tuff, sandstone, and andesite in seven water saturation conditions between almost completely dried and water saturated. These conditions were controlled by varying the time the specimens were submerged in water and then dried. The test results showed that the Brazilian tensile strength of the tuff and the sandstone increases with a decrease of water saturation and then tends to be constant in very low water saturation conditions. In contrast, the Brazilian tensile strength of the andesite consistently increased with a decrease of water saturation. This trend for each of the rocks was also observed in the Young’s modulus estimated from the load–displacement curves in the Brazilian tension tests as well as the uniaxial compressive strength obtained in the previous studies. The applicability of the Hertz contact theory to the Brazilian tension tests with these rocks in various water saturation conditions was validated by comparing the estimated and measured Young’s modulus and by relating the Young’s modulus and the strength. The results in this study are helpful for estimating the strength and Young’s modulus of rocks in various water saturation conditions and for assessing the stability of underground structures.