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高应力巷道围岩板裂−岩爆模拟试验及声发射频域研究

Experimental study and acoustic emission frequency domain analysis of spalling-rockburst in high-stress tunnel surrounding rock

  • 摘要: 为了揭示高应力环境下巷道围岩的板裂−岩爆破坏机制, 针对深埋巷道赋存的“高地应力+应力调整”环境, 在实验室内对含圆形通孔的灰岩试样进行真三轴试验。试验过程中, 采用微型摄像机和声发射监测系统记录试样孔洞产生的宏观破坏现象及其内部微观损伤释放的瞬态弹性波。通过快速傅里叶变换将声发射波形从时域转换到频域, 建立了表征频率能量迁移特性的FR参数, 重点研究了巷道围岩的板裂−岩爆破坏过程及其对应的声发射频域信息演化规律。研究结果表明: 巷道围岩的板裂−岩爆破坏过程可分为平静阶段、小颗粒弹射阶段、板裂剥落阶段和岩爆喷射阶段; 在板裂−岩爆过程中, 垂直应力引起的张性破坏和水平应力引起的剪性破坏共同作用, 导致了“V”形岩爆坑的形成; 通过声发射峰值频率和频率质心可将信号进一步分为低频信号、次低频信号、次高频信号和高频信号, 分别对应岩石内部不同的裂纹尺度和破坏模式; 不同频率信号的共现现象和FR参数的阶跃特征, 反映了岩石内部结构的剧烈变化; 岩爆的发生主要取决于围岩的应力状态和岩体的储能极限, 板裂作为岩爆的充分不必要条件, 促进了岩爆的演化。

     

    Abstract: To elucidate the spalling-rockburst mechanisms in tunnel surrounding rock under deep, high-stress environments, true triaxial loading tests were conducted on limestone specimens with circular through-holes. These experiments simulated the conditions of deep-buried tunnels subjected to ''high geostress + stress adjustment''. A micro-camera and an acoustic emission(AE) monitoring system were used to record the macroscopic failure phenomena around the boreholes and the transient elastic waves released by micro-damage. The AE waveforms were transformed from the time domain to the frequency domain using Fast Fourier Transform (FFT), and the frequency energy migration was characterized by establishing the FR parameter. The study focused on the spalling-rockburst failure process and the evolution of frequency-domain acoustic emission signals. Results indicate that the spalling-rockburst process of the surrounding rock can be divided into four stages: the quiet stage, particle ejection stage, spalling detachment stage, and rockburst ejection stage. Tensile damage induced by vertical stress and shear damage caused by horizontal stress jointly contribute to the formation of a "V"-shaped rockburst crater. The peak frequency and frequency centroid of AE signals classify them into four types: low-frequency, sub-low-frequency, sub-high-frequency, and high-frequency signals, corresponding to different crack scales and damage modes in the rock. The co-occurrence of these frequency signals and the stepwise changes in FR parameters reflect significant internal structural changes within the rock. Rockburst occurrence is primarily determined by the stress state of the surrounding rock and the energy storage capacity of the rock mass. While spalling is a sufficient but not necessary condition for rockburst, it accelerates its evolution.

     

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