A framework for the discontinuum-based simulation of spalling failure in rock tunnels is proposed. This innovation involves the combined application of the damage-initiation and spalling-limit (DISL) approach with the hybrid lattice/discrete element method (LDEM), a special bonded-block modeling technique that incorporates Rigid Body Spring Network lattice bonds between stochastically generated Voronoi cells. First, verification analyses are conducted to understand the deformability and strength behaviors of the LDEM models via unconfined-compression, triaxial, and direct-tension tests on numerical granite and limestone models. The results reveal that LDEM does not require a calibration procedure to define Young’s moduli, Poisson’s ratios, tensile strengths, and damage-initiation strength envelopes of the models. Moreover, an equation that relates tensile strength and fracture toughness with the mesh size of the model was derived from tension tests on center-cracked specimens. Subsequently, the DISL-LDEM was applied to two rock tunnel spalling cases, i.e., a square tunnel in Cobourg limestone and the circular Mine-by Experiment tunnel in Lac du Bonnet granite. In-situ observations, finite-element analyses, and empirical data were used to compare the simulated failure modes and spalling-breakout dimensions. Using the results obtained from the study cases, a framework for DISL-LDEM simulations of underground excavations was established. Notably, this novel approach does not require trial-and-error simulations and establishes a clear one-to-one relationship between each numerical input parameter and model behavior. Therefore, the proposed framework acts as a practical numerical tool for discontinuum-based simulations of spalling in rock tunnels.

中文翻译：

---

岩石隧道剥落破坏的混合晶格/离散元分析


提出了一种基于间断面的岩石隧道剥落破坏模拟框架。这项创新涉及损伤起始和剥落极限 (DISL) 方法与混合晶格/离散元方法 (LDEM) 的结合应用，这是一种特殊的粘结块建模技术，在随机生成的 Voronoi 之间结合了刚体弹簧网络晶格键细胞。首先，通过对数值花岗岩和石灰岩模型进行无侧限压缩、三轴和直接拉伸试验，进行验证分析，以了解 LDEM 模型的变形能力和强度行为。结果表明，LDEM 不需要校准程序来定义模型的杨氏模量、泊松比、拉伸强度和损伤起始强度包络线。此外，通过对中心裂纹样品的拉伸试验得出了将拉伸强度和断裂韧性与模型网格尺寸联系起来的方程。随后，DISL-LDEM 被应用于两个岩石隧道剥落案例，即 Cobourg 石灰岩中的方形隧道和 Lac du Bonnet 花岗岩中的圆形 Mine-by Experiment 隧道。使用现场观察、有限元分析和经验数据来比较模拟的失效模式和剥落断裂尺寸。利用从研究案例中获得的结果，建立了地下开挖 DISL-LDEM 模拟框架。值得注意的是，这种新颖的方法不需要反复试验模拟，并且在每个数值输入参数和模型行为之间建立了清晰的一对一关系。因此，所提出的框架可作为基于不连续体的岩石隧道剥落模拟的实用数值工具。