In this paper, firstly, uniaxial compression test and Brazilian test of rock were conducted to investigate the influence of surrounding non-atmospheric environments on uniaxial compressive strength and tensile strength. The environments used in this paper were organic vapor, inorganic gas and water vapor. As the results, it was founded that water vapor is the most effective agent which promotes stress corrosion for rocks. Then, a series of uniaxial compression tests, Brazilian tests and Semi-Circular Bend tests of rocks under various water vapor pressures was conducted to investigate the influence of the surrounding water vapor environment on uniaxial compressive strength, tensile strength and fracture toughness. The rocks used in this paper were Kumamoto andesite, African granodiorite and Korean granite. It was made clear that rock strengths and fracture toughness of these rocks are dependent on the water vapor pressure in the surrounding environment and decrease with increasing the pressure.
Strengths of a rock are dependent on not only the properties of rock itself but also the surrounding environment, such as temperature, humidity, confining pressure and so on. Furthermore, it has been known that fracture of a rock takes place owing to the subcritical crack growth caused by stress corrosion under the stress state below the strengths of the rock. The stress corrosion is the chemical reaction activated by stress concentration at a crack tip. The water vapor is considered to be a chemical reaction agent in the stress corrosion for silicate materials like a rock (Freiman 1984, Atkinson & Meredith 1979). Therefore it is desired that the influence of the water vapor on rock strengths is taken into account based on the results obtained from various experiments.
In this paper, firstly, uniaxial compression (UC) test and Brazilian test were conducted on Kumamoto andesite to investigate the influence of surrounding non-atmospheric environments on uniaxial compressive (UC) strength and tensile strength (Jeong et al. 2007). The environments used in this paper were methanol, ethanol and acetone vapor as organic vapor, argon, nitrogen and oxygen as inorganic gas and water vapor, using special vacuum chamber. Then it was found that the water vapor is the most effective environment which promotes decreasing of the strengths, namely stress corrosion for rocks. Secondly, fracture toughness of various types of rock was estimated under various water vapor pressures in surrounding environment, as well as UC and tensile strengths. Semi-Circular Bend (SCB) test (Chong & Kuruppu 1984) was adopted to estimate the fracture toughness of rock for its simplicity of specimen preparation, equipment and testing procedure. The Kumamoto andesite, African granodiorite and Korean granite were used in the SCB test (Kataoka et al. 2011).