With the construction of deep underground openings, the formation of excavation failure zone and its prediction have become a focus of rock mechanics in deep underground excavation both in China and abroad. Based on the analysis of mechanical properties of hard rocks during their failure process, the conventional continuum models and the cohesion weakening-friction strengthening ( CWFS ) model were compared. Numerical analysis of a circular test tunnel in a Mine-by Experiment at the URL in Canada was carried out by using FLAC with elastic-perfectly plastic, elastic brittle, strain softening and CWFS constitutive models, respectively. The results of comparison of stress distribution, principal stress values at key points and plastic region among different models show that CWFS model can simulate the stress transfer and stress concentration to a deep area, which is the real situation when stress-induced failure occurs; the stress distribution calculated from CWFS model is much closer to that when the excavation failure zone is deleted. Compared to other models, the extent and depth of excavation failure zone calculated by CWFS are larger and they are in agreement with the field measurements. Finally, the CWFS model was used to investigate the failure zone in another case, the Kobbskaret road tunnel in Norway. The depth and extent of the excavation failure zone were predicted rather well and it again proves the rationality of using CWFS model in predicting the excavation failure zone of hard rocks in deep tunnels.%随着深部地下洞室的大量兴建,深部开挖过程中开挖破坏区的形成及其预测成为国内外岩石力学研究的焦点.本文首先对硬岩破坏过程的力学特性进行了分析,在此基础上对当前岩石力学工程界惯常采用的连续介质模型和粘聚力弱化-摩擦强度强化(CWFS)模型进行了比较；利用岩土工程分析软件FLAC,采用理想弹塑性、弹脆塑性、应变软化及CWFS模型对加拿大Mine-by Experiment圆形试验洞室进行了数值分析,通过对围岩应力分布、关键点应力大小和塑性区分布的对比分析,发现CWFS模型计算得到的应力场更能准确反映破坏区产生后应力向围岩深部转移并集中的特征；这一应力分布特征与开挖破坏区不存在时的结果更接近；与其它模型相比,CWFS模型计算得到的破坏区范围和深度更大,与现场实测值更加吻合.最后采用CWFS模型对挪威Kobbskaret公路隧道破坏区大小进行了计算分析,再次验证了采用CWFS模型对硬岩开挖破坏区预测的合理性.
展开▼
