Fracture mechanics analysis of shear band propagation requires knowledge of the material’s shear fracture energy and its related properties such as the characteristic slip displacement. Yet these properties of stiff clays and shales have not been investigated systematically. This work characterizes and analyzes the shear fracture energies and characteristic slip displacements of various stiff clays and shales based on their triaxial compression data from the literature. A methodology originally developed for hard rocks was adopted for this purpose. Results show that the shear fracture energies of stiff clays and shales generally increase with the effective normal stress on the slip plane, varying by orders of magnitude—approximately from \(4\times 10^{1}\) to \(7\times 10^{3}\) J/m\(^{2}\)—in the range of effective normal stresses from \(10^{2}\) to \(10^{5}\) kPa. An empirical equation is presented for a first-order estimate of the shear fracture energy under a given effective normal stress. The characteristic slip displacements at the laboratory scale are calculated to be smaller than 6 mm, and they appear independent of the effective normal stress. Compared with their nominal values calculated without considering the change of normal stress in triaxial tests, the shear fracture energies are approximately 70% of the nominal values, whereas the characteristic slip displacements are nearly identical to the nominal ones.

剪切带传播的断裂力学分析需要了解材料的剪切断裂能及其相关特性，例如特征滑移位移。然而，尚未系统地研究硬质粘土和页岩的这些特性。这项工作基于文献中的三轴压缩数据，对各种硬质粘土和页岩的剪切断裂能和特征滑移位移进行了表征和分析。为此，采用了最初为硬岩开发的方法。结果表明，硬质粘土和页岩的剪切断裂能通常随滑移面上的有效法向应力而增加，幅度在数量级上变化-从\（4×10 ^ {1} \）到\（7 \ times） 10 ^ {3} \）  J / m\（^ {2} \） —在有效法向应力范围从（10 ^ {2} \）到\（10 ^ {5} \）  kPa的范围内。为给定有效法向应力下的剪切断裂能的一阶估计提供了经验方程。计算得出的实验室规模的特征滑移位移小于6 mm，并且它们看起来与有效法向应力无关。与不考虑三轴试验中法向应力变化而计算出的标称值相比，剪切断裂能约为标称值的70％，而特征滑移位移几乎与标称值相同。