| Research Abstract |
The strength of rocks is affected by the density, the shape and the direction of cracks, the strain and stress rate of loading, the stress state, the temperature and the existence of water in vapor phase or in liquid phase, and so on. Many researchers have indicated that the strength of rocks is dependent on the suberitical crack growth due to stress corrosion.
The stress corrosion crack growth occurs because the chemical action of an environmental agent, such as water, weakens the strained bonded at crack tips and facilitates crack propagation, and the crack velocity as a stress intensity factor is exceeded the stress corrosion limit increases with increasing water vapor pressure. Charles, Krokosky et at. and Mizutani et al. have shown the experimental results that the strength of rocks under uniaxial compression test increases with decreasing water vapor pressure in atmosphere. Accordingly, it is considered that the strength of rocks may be controlled by surrounding environment of roc
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ks, based on the above facts.
In this research, to examine the influence of non-atmospheric environment, namely water, acetone, ethanol, methanol in vapor phase and hydrogen as the stress corrosion agent, on the strength of rock, uniaxial compression test and disc lest under the vapor pressure of the range from 10^<-3> to 10^6 Pa are conducted on Kumamoto andesite.
From the experimental results, it is made clear that tie compressive and tensile strength of Kumamoto andesite increases with decreasing the water vapor pressure and that water is tie most effective agent which promotes the stress corrosion among them. Since the degree of influence of these materials on the compressive strength is the same as that on the tensile strength, it is considered that the mechanism of the fracture under compressive and tensile stress state is almost the same. Finally, it is shown that the strength of rock under inorganic gas environment, like hydrogen, Argon, nitrogen and oxygen, is two times as much as that under the same water vapor pressure. Less
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