Li Zixuan, Huang Shiyuan, Lv Chuan, Liao Cheng, Li Xudong, Du Hongbo
Engineering Research Center of Diagnosis Technology and Instruments of Hydro-Construction, Chongqing Jiaotong University, Chongqing 400074, China.
School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074, China.
Materials (Basel). 2024 Dec 4;17(23):5941. doi: 10.3390/ma17235941.
Understanding fracture mechanics in rock-like materials under compression-shear condition is critical for predicting failure mechanisms in various engineering applications, such as mining and civil infrastructure. This study conducted uniaxial compression tests on cubic gypsum specimens of varying sizes (side lengths of 75 mm, 100 mm, 125 mm, and 150 mm) and crack inclination angles (ranging from 0° to 90°) to assess the size effect on fracture behavior. The effects of specimen size and crack inclination on fracture characteristics, including strength, failure mode, and crack initiation angle, were analyzed based on the maximum tangential stress (MTS) criterion and the generalized maximum tangential stress (GMTS) criterion, with relative critical size (α) and relative openness (). Results indicate that the crack initiation angle increases with crack inclination, while compressive strength decreases significantly with increasing specimen size. For example, at a 30° crack inclination, the peak compressive strength of 75 mm specimens was 2.53 MPa, whereas that of 150 mm specimens decreased to 1.05 MPa. Crack type and failure mode were found to be primarily influenced by crack inclination rather than specimen size. The experimental crack initiation angle aligned with the theoretical crack initiation angle at inclinations below 50° but diverged at higher inclinations. A linear relationship was established between and specimen size () under compression-shear stress, expressed as rc=-0.01772L+3.54648; larger specimens exhibited increased tangential stress at the crack tip, leading to earlier macroscopic crack formation, while decreased as specimen size increased. These results underscore the significant influence of size on fracture behavior in quasi-brittle materials under compression-shear stress, providing essential insights for predicting material failure in rock-like structures.
了解类岩石材料在压缩-剪切条件下的断裂力学对于预测采矿和土木基础设施等各种工程应用中的破坏机制至关重要。本研究对不同尺寸（边长分别为75毫米、100毫米、125毫米和150毫米）和裂纹倾斜角度（范围为0°至90°）的立方石膏试样进行了单轴压缩试验，以评估尺寸对断裂行为的影响。基于最大切向应力（MTS）准则和广义最大切向应力（GMTS）准则，结合相对临界尺寸（α）和相对张开度（），分析了试样尺寸和裂纹倾斜对断裂特性（包括强度、破坏模式和裂纹起裂角度）的影响。结果表明，裂纹起裂角度随裂纹倾斜度增加而增大，而抗压强度随试样尺寸增大而显著降低。例如，在裂纹倾斜度为30°时，75毫米试样的峰值抗压强度为2.53兆帕，而150毫米试样的峰值抗压强度降至1.05兆帕。发现裂纹类型和破坏模式主要受裂纹倾斜度而非试样尺寸的影响。在倾斜度低于50°时，实验裂纹起裂角度与理论裂纹起裂角度一致，但在较高倾斜度时出现偏差。在压缩-剪切应力作用下，建立了与试样尺寸（）之间的线性关系，表达式为rc = -0.01772L + 3.54648；较大的试样在裂纹尖端表现出更大的切向应力，导致更早形成宏观裂纹，而随着试样尺寸增加而减小。这些结果强调了尺寸对准脆性材料在压缩-剪切应力下断裂行为的显著影响，为预测类岩石结构中的材料破坏提供了重要见解。
