中文摘要：

岩石断裂韧度表征其抵抗裂纹起裂和扩展的能力,作为其力学性能的一个重要指标,在岩石力学理论研究与岩体工程应用中有着不可替代的作用。由于岩石结构的复杂性,其破坏形式大多呈现为复合型断裂破坏,研究复合型加载条件下岩石断裂韧度具有重要的意义。为了研究锈岩的断裂力学性能,以便其在建筑工业中得到更为广泛的应用,通过18个中心裂纹圆盘（CSTBD）试件径向受压试验,进行了复合型加载条件下锈岩断裂韧度的试验研究。测得了锈岩在纯I型,纯II型以及复合型加载时的断裂韧度,并将试验结果与基于广义最大周向应力（GMTS）准则的理论值进行了对比分析,结果表明：锈岩的纯I型断裂韧度为1.01 MPa·m-（0.5）,而纯II型断裂韧度为1.51 MPa·m-（0.5）,是纯I型断裂韧度的1.49倍,这与基于GMTS准则的理论值1.34非常接近,而比基于最大周向应力（MTS）准则的理论值0.87大很多。裂纹尖端附近的T应力及断裂过程区裂纹尖端的临界距离r_c对岩石类材料的开裂路径以及复合型断裂韧度都有较大的影响。考虑了T应力的广义最大周向应力（GMTS）准则能很好的预测试验结果。

英文摘要：

Fracture toughness of rocks characterizes the resistance to crack initiation and propagation. As an important index of mechanical property, it plays an irreplaceable role in the theoretical research of rock mechanics and practical application to rock engineering problems. Due to the complexity of rock structures, most of rock fractures occur under mixed mode loading conditions. Therefore, it is important to investigate the mixed mode fracture toughness of rocks. Rust rocks are widely used in the construction, and thus are selected to study the fracture behavior. A series of radial compression tests is carried out on 18 cracked straight through Brazilian disc（CSTBD） specimens to obtain the pure mode I, pure mode II and mixed mode I/II fracture toughness. Then experimental results are compared with theoretical values calculated by the generalized maximum tangential stress（GMTS） criterion. The results show that the values of fracture toughness for pure mode I and pure mode II are 1.01 MPa·m-（0.5） and 1.51 MPa·m-（0.5）, respectively. The fracture toughness of pure mode II is 1.49 times higher than that of the pure mode I. The fracture toughness of pure mode II is close to the value of 1.34 obtained by the GMTS criterion, but is larger than the value of 0.87 achieved by the maximum tangential stress（MTS） criterion. The T-stress and the critical distance（r_c） related to the size of fracture process zone in front of the crack tip have a great influence on crack propagation path and mixed mode fracture toughness of rock materials. As the generalized maximum tangential stress（GMTS） criterion takes into account the T-stress, it has a good agreement with experimental results.