砂岩のサブクリティカルき裂進展に及ぼす湿度の影響

抄録

The effect of the humidity on subcritical crack growth in sandstone in air was investigated experimentally. Rocks used in this study were Berea sandstone, Shirahama sandstone and sandstone obtained at Kushiro coalmine (Kushiro sandstone). Double-Torsion method was used in this study to measure the crack velocity and the stress intensity factor. All experiments were conducted under the same temperature and different relative humidity to investigate the effect of the humidity.
It was shown that the humidity affected the crack velocity strongly. The crack velocity increased with the increase of the humidity. The increases of the crack velocity were much larger than that estimated from the classical stress corrosion theory. The increases of the crack velocity in Shirahama sandstone and Kushiro sandstone were larger than that in Berea sandstone by several orders of magnitude. This difference may be due to the difference of the rock fabric. Shirahama sandstone and Kushiro sandstone include clay minerals much more than Berea sandstone. It is probable that the fracture resistance of clay decreased due to the increase of the humidity. Consequently, large increases of the crack velocity occurred in Shirahama sandstone and Kushiro sandstone. It is concluded that the humidity has the strong effect on subcritical crack growth in sandstone and the control of the humidity is important to prevent the weakening of rock.