水岩作用下岩石亚临界裂纹的扩展规律

Subcritical crack growth of rock during water-rock interaction

采用双扭试件,利用常位移松弛法,分别进行自然状态以及水岩作用下大理岩和混合岩的亚临界裂纹扩展实验,获得2种环境下岩石裂纹扩展速率v与应力强度因子KI的关系,并计算得到亚临界裂纹扩展参数A和n。通过对比,研究水对岩石亚临界裂纹扩展规律的影响。研究结果表明:对于大理岩,其A为自然状态下的8.07×1016倍,n由自然状态下的48.33下降到8.28;对于混合岩,其A为自然状态下的5.45×109倍,n则由自然状态下的60.20下降到21.86,说明对应于同一应力强度因子水平,水作用下的岩石亚临界裂纹扩展速度要快;水的存在使得岩石的断裂韧度KIC明显降低,对于大理岩,自然状态下的KIC为3.0316MN/m3/2,水岩作用后KIC为2.2070MN/m3/2,下降27.19%;对于混合岩,2种状态下的KIC分别为2.0877和1.9398MN/m3/2,下降7.08%。该实验结果可为复杂矿岩的稳定性分析提供可靠依据。

By adopting the double-torsion load-relaxation method at constant displacement, two kinds of rocks were tested to get the parameters of subcritical crack growth and fracture toughness （K1C）. In order to compare the parameters of rocks in different environments, the test specimens were divided into two groups： one group was immersed in groundwater and the other in air. The relations of the stress intensity factor K1 and the subcritical crack growth velocity v were obtained by test, and the subcritical crack growth parameters A and n were also obtained. The behavior of subcrtical crack growth in different environments was analyzed. The results show that compared with marble specimens in natural state, .4 increases in 8.07 × 10^16 folds but n decreases from 48.33 to 8.28 because of the water-rock interaction. And in migmatite test, A also increases in 5.45×10^9 folds and n decreases from 60.20 to 21.86. Meanwhile, the fracture toughness KIC also decreases obviously due to water effect. The Kic of marble is 3.031 6 MN/m^3/2 in air and 2.207 0 MN/m^3/2 in water, and it decreases by 27.19%. And for migmatite, the KIC is 2.087 7 M-N/m^3/2 in air and 1.939 8 MN/m^3/2 in water, decreases by 7.08%, which shows that the water-rock interaction speeds up the subcritical crack growth. Reliable references are provided by the testing results for studying time-dependent of rock stability.