弱胶结软岩巷道开挖扰动应力旋转特征及支护对策
Stress rotation of weakly-cemented soft rock during roadway excavation and its support strategies
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摘要: 针对西部矿区弱胶结软岩地层巷道围岩自稳能力差、变形大、支护易失效等问题, 采用室内试验、数值模拟、现场监测和理论分析相结合的方法, 分析了开挖过程中围岩主应力旋转特征, 提出针对弱胶结软岩巷道的支护对策。研究结果表明: 巷道开挖过程中, 巷道围岩主应力旋转幅度经历了平稳增长。剧烈扰动和恢复平稳3个阶段。在工作面推进至监测断面时围岩主应力调整最为剧烈, 其中顶板和底板最大主应力增加至初始值的1.62倍, 帮部增加至初始值的1.35倍; 顶板和底板最大主应力倾角/方位角在岩壁处分别为30°/41°和23°/151°。随远离岩壁, 最大主应力倾角/方位角呈先增大后减小的趋势, 并且在距离巷道岩壁0.68R处倾角/方位角的变化达到峰值11°/5°、14°/176°; 帮部最大主应力旋转角度随远离岩壁呈减小的趋势, 倾角/方位角由56°/58°变化至初始状态, 分别旋转了34°和32°; 顶板围岩应力旋转幅度大于底板和帮部。基于巷道开挖扰动应力旋转特征, 提出了考虑主应力旋转效应的弱胶结巷道锚杆(索)+金属网的非对称耦合支护技术, 并进行了数值模拟分析和现场工业试验。现场结果表明: 采用非对称耦合支护技术可以显著改善围岩应力状态, 有效减小巷道围岩塑性范围, 控制弱胶结软岩巷道变形。Abstract: To address the engineering challenges posed by poor self-stabilization, significant deformation, and support prone to failure of the weakly-cemented soft rock during roadway excavation, the laboratory test, numerical simulations, field monitoring and theoretical analysis were performed to investigate the principal stress rotation of the surrounding rock during roadway excavation and then asymmetrical coupling support strategies were explored. The results show that the principal stress of surrounding rock during tunnel excavation rotates by three stages: steady growth, severe disturbance, and restoration of stability. The adjustment of the principal stress is most pronounced when approaching the monitoring section at the working face. The major principal stress in the roof and floor increases to 1.62 times the initial value and that of the side walls to 1.35 times the initial value. At the rock wall, the dip angles/azimuths of the major principal stresses on the top and bottom plates are 30°/41° and 23°/151°, respectively. With the increase of the distance from the rock wall, the dip angles/azimuths exhibit a trend of first increase and then decrease, achieving the peak at 11°/5° and 14°/176° at a distance of 0.68 times the diameter from the rock wall. Conversely, the rotation angle of the major principal stress on the side walls decreases with the distance, where dip angles/azimuths change from 56°/58° to the initial state, rotating by 34° and 32°, respectively. The stress rotation amplitude in the roof surrounding rock is greater than those in the bottom and sides. An asymmetric coupling support technology was proposed. Furthermore, numerical simulation analysis and on-site industrial tests verified that this asymmetric coupling support technology can significantly enhance the stress state of surrounding rock, effectively reduce the plastic zone, and provide better control over the deformation of roadways in weakly-cemented soft rock.