Elastic parameters and the subcritical crack growth of different bedding angle slate specimens were studied using uniaxial compression testing and the double torsion constant displacement load relaxation method using SANS and MTS Insight machines. To study the relations of the mode-I stress intensity factor versus the subcritical crack growth velocity , the fracture toughness , the stagnation speed, and the threshold values, the double torsion constant displacement load relaxation method was carried out. The related rules between the bedding angles (β) and the uniaxial compressive strength, fracture toughness, and threshold values were investigated. Experimental results show that the uniaxial compression, the fracture toughness, and the threshold value curves move to the bottom then increase with the increase of the β angle. In addition, its fracture toughness is minimal when the β angle of the slates is 45°, and crack initiation and crack propagation are generated under load, which can lead to the failure of the slate. - relations of transversely isotropic slates measured by this method are in accordance with linear rules, which is in good agreement with the Charles theory. The range of for these different bedding angle slates is from 0.511 to 0.789. The test results would provide the basis for studying seepage and time-dependency of rock engineering stability.

中文翻译：

---

横向各向同性板岩亚临界裂纹扩展及阈值的相关规律研究

使用单轴压缩试验和使用 SANS 和 MTS Insight 机器的双扭转恒位移载荷松弛方法研究了不同层理角度板岩试样的弹性参数和亚临界裂纹扩展。为了研究I型应力强度因子与亚临界裂纹扩展速度、断裂韧性、停滞速度和阈值的关系，采用双扭转恒位移载荷松弛法。研究了层理角度（β）与单轴抗压强度、断裂韧性和阈值之间的相关规律。实验结果表明，随着β角的增加，单轴压缩、断裂韧度和阈值曲线向底部移动然后增加。此外，当板岩的β角为45°时，其断裂韧性极小，在载荷作用下会产生裂纹萌生和裂纹扩展，从而导致板岩失效。——该方法测得的横向各向同性板岩关系符合线性规律，与查尔斯理论吻合较好。这些不同层理角度板岩的范围是从 0.511 到 0.789。试验结果可为研究岩石工程稳定性的渗流及时效性提供依据。这与查尔斯理论非常吻合。这些不同层理角度板岩的范围是从 0.511 到 0.789。试验结果可为研究岩石工程稳定性的渗流及时效性提供依据。这与查尔斯理论非常吻合。这些不同层理角度板岩的范围是从 0.511 到 0.789。试验结果可为研究岩石工程稳定性的渗流及时效性提供依据。