岩石蠕变断裂特性的试验研究

以一类红砂岩为例对蠕变条件下岩石裂纹的起裂和扩展的机理、准则进行了试验研究和理论分析．试验结果表明，岩石裂纹常常在初始应力强度因子KI小于断裂韧度KIC的情况下，经过一段时间的持续蠕变变形产生裂纹起裂和扩展．当然，初始应力强度因子KI小于断裂韧度KIC是有限度的，KI不得小于另一固定值KIC2，KIC2表征了岩石在蠕变条件下抵抗裂纹起裂和扩展的能力，而且其值小于KIC，可称之为蠕变断裂韧度．在岩石工程的设计和计算中，KIC2是一个重要参数．

THE EXPERIMENTAL STUDY ON CREEP FRACTURE OF ROCK

The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers. And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers. The characteristics of crack initiation and propagation of rocks under creep condition, however, are very important for rock engineering and still not paid enough attention by researchers. In this paper, the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in Emei Mountain, the Sichuan Province of China. Cuboid specimens under three point bending were used in this investigation. All specimens were classified into four sorts and used for Mode-I fracture or creep fracture tests. The experimental result shows that due to creep deformation, rock crack will inevitably initiate and propagate under a load of K1, which is less than fracture toughness KIC but not less than a constant (marked as KIC2). KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture toughness KIC, it is defined as creep fracture toughness in this paper. KIC2 should be considered as an important parameter on design and computation of rock engineering.