开挖断面曲率半径对高应力下硬脆性围岩板裂化的影响

Influence of curvature radius of tunnels excavation section on slabbing of hard brittle rockmass under high stress

围岩板裂化是深埋高地应力条件下硬脆性围岩开挖后出现的一种典型破坏形式。影响围岩板裂化形态和形成机制的因素很多,开挖断面的曲率半径是其中的关键因素之一。为了研究开挖断面曲率半径对深部硬脆性围岩板裂化的影响,首先总结、分析了锦屏二级水电站深埋隧洞不同开挖断面曲率半径所对应的板裂化形态和特征。在此基础上,设计了室内物理模型试验,研究不同孔径的圆形洞室和不同尺寸的直墙拱洞室在平面应变条件下的板裂化破坏形态。研究结果表明,开挖断面的曲率半径对围岩板裂化的影响机制表现在尺度效应和结构效应两个方面,影响着板裂化的破坏形态和破裂机制,当同一洞室断面包含不同曲率半径段时,板裂化破坏表现出曲率半径影响下的组合破坏特征。最后,利用数值模拟结果分析和验证了开挖断面曲率半径对围岩板裂化的影响效应。

Generally, slabbing is the typical failure mode when the hard brittle rockmass in deep tunnel is excavated under the condition of high stress. Many factors are contributed to the form and formation mechanism of slabbing, in particular the curvature radius of the excavated section. Therefore, the influence of curvature radius on the hard brittle slabbing is firstly summarized and analyzed the slabbing form and feature corresponding to curvature radius of different sections in deep tunnel of Jinping II hydropower station. Subsequently, the indoor physical model test is designed to investigate the slabbing forms of circular caves with different bore diameters and straight-wall arch caves with different sizes under plane strain condition. The results show that the slabbing mechanisms influenced by the curvature radius can be demonstrated at both scale and structural effects, which jointly affect fracture morphology and fracture mechanism of slabbing. When the sections in the same tunnel consist of different curvature radii, slabbing failure presents combinated characteristics of fracture. Finally, the mechanisms of slabbing influenced by curvature radius are analyzed and verified by numerical simulation.