中文摘要：

实际工程中,结构体裂纹常处于拉剪和压剪复合受力状态,研究适合于复合型裂纹的断裂准则和裂纹扩展机理具有重要的理论意义和实用价值。以Ⅰ-Ⅱ复合型裂纹为研究对象,基于线弹性理论,在考虑裂纹几何特征及受力形式的基础上,系统介绍了裂纹应力强度因子（SIF）的理论解。提出了适用于Ⅱ型断裂的径向剪应力准则和双剪应力准则。对于Ⅰ-Ⅱ复合型裂纹,提出用等效Ⅰ、Ⅱ型SIF比值与Ⅰ、Ⅱ型断裂韧度比值的关系判定裂纹断裂类型,并分别选择适合于Ⅰ、Ⅱ型断裂的断裂准则,计算了裂纹断裂扩展理论角度。理论断裂角与预制非闭合裂纹类岩石脆性材料压剪断裂试验结果符合得较好。

英文摘要：

In practical projects, structural fracture often undergoes complex stresses. The studies on the fracture mechanism of mixed mode cracks are of important theoretical significance and practical implication. Based on the mixed Ⅰ–Ⅱ crack mode and the linear elastic theory, the geometrical characteristics and stress form of cracks are considered, and the theoretical solution of the stress intensity factor（SIF） at the crack tip is introduced. The radial shear stress criterion and the twin shear stress criterion for mode Ⅱ fracture are put forward. For the Ⅰ–Ⅱ mixed-mode open crack, a new method to determine the fracture type is proposed by comparing the SIF ratio of equivalent mode Ⅰ and Ⅱ with that of mode Ⅰ and Ⅱ fracture toughness. In addition, an appropriate fracture criterion for mode Ⅰ or Ⅱ fracture is used to calculate the theoretical initiation angle. The compression-shear fracture tests on the brittle rock-like samples with a single open pre-crack are carried out under compression. The results indicate that the theoretical initiation angles and the experimental results are in good agreement.