Experimental Study on Stress Corrosion and Vacuum Effect of Rocks

21世纪初，日本将在深度超过1000米的岩体内建造用于放射性废物处置的大型岩洞。这种大型岩洞的稳定性必须在很长时间内得到保证。岩石的长期强度预测是保证岩洞长期稳定的必要条件。岩石在压缩下的强度受岩石的密度、裂缝的形状和方向、加载的应变和应力速率、应力状态、温度以及是否存在气相或液相水等因素的影响。一些研究者认为岩石的强度取决于应力腐蚀引起的亚临界裂纹扩展，并与大气中的水蒸气压成正比。然而，很少有实验来证实这一事实。为了研究水作为应力腐蚀剂对岩石强度的影响，对北岛花岗岩和熊本安山岩进行了10^<-3> ~ 10^3 Pa水蒸汽压力范围内的单轴压缩试验。在此基础上，确定了岩石的应力腐蚀指标，讨论了岩石长期强度的估计。主要研究结果如下：1。通过分析得到的应力应变曲线，得到弹性模量不受水蒸气应力腐蚀的影响。两种岩石的单轴抗压强度随水蒸气压的减小而增大。结果表明，这种效应与应力腐蚀有关。基于单轴抗压强度与水汽压的关系，得到熊本安山岩的应力腐蚀指数为36，北岛花岗岩的应力腐蚀指数为61。该线性关系适用于水蒸汽压10^<-3> ~ 10^ 3pa4的范围。讨论了岩石长期强度的估计问题。发现诱发应力腐蚀的因素是评价岩洞长期稳定性的必要条件。少

At the beginning of the twenty one century, the large rock cavern for radioactive waste diaposal will be constructed within a rock mass at a depth of more than 1000m, in Japan. The stability of such large rock cavern must be guarantee over very long timescale. The prediction of long-term strength of rocks is indispensable for insuring long-term stability of the rock cavern.The strength of rocks under compression 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. Some researchers have inducated that the strength of rocks in dependent on the subcritical crack growth due to stress corrosion and is proportional to the water vapor pressure in atmosphere. However, few experiments to verify this fact have been performed.In this research, to examine the influence of the water as the stress corrosion agent on the strength of rocks, a … More series of uniaxial compression tests under the water vapor pressure ranging from 10^<-3> to 10^3 Pa is conducted on Kitagishima granite and Kumamoto andesite. Furthermore, the stress corrosion index is determined, then the estimation of long-teem strength of rock is discussed. The main results obtained are follows :1.The elastic modulus are not affected by the stress corrosion due to water vapor, analyzing the stress strain curve obtained.2.The uniaxial compressive strength of both rocks increases with decreasing water vapor pressure. It is clarified that this effect is dependent on the stress corrosion.3.The values of the stress corrosion index obtained from the results are 36 in Kumamoto andesite and 61 in Kitagishima granite, based on the relation between uniaxial compressive strength and water vapor pressure. The linear relation is applicable to the range of water vapor pressure 10^<-3> to 10^3 Pa.4.The estimation of long-term strength of rock is discussed. The discover of an agent activating the stress corrosion is indispensable to estimate the long-term stability of rock cavern. Less