加载速率影响下类硬岩声发射及破裂响应特征

Acoustic emission characteristics and fracture response behavior of hard rock-like material under influence of loading rate

  • 摘要: 为明确硬岩破坏失稳过程中的声学及破裂响应特征与加载速率相关性,对不同加载速率下类硬岩岩样进行单轴压缩试验及声发射测试,分析类硬岩力学参数特性、声发射现象及破裂响应特征,并基于声发射特征获得类硬岩破坏前兆预警信息。结果表明:类硬岩的峰值强度、弹性模量和峰值应变具加速率效应;随着加载速率增大,力学参数总体呈指数函数增长,相对低加载速率下(0.10~0.15 kN/s)的增长速率较快而在相对高加载速率下(0.20~0.25 kN/s)的增长速率略有减缓;声发射参数演化呈阶段性增长趋势,最大增幅与加载速率呈正相关;随着加载速率增大,AE幅度和幅度密度逐渐增大,AE振铃计数由低值低频向高值高频转变,AE能量由孤震型向群震型转变;加载速率对破裂模式及破碎形态具有明显影响,随着加载速率增大岩样由剪切破坏逐渐向拉伸剪切复合破坏、拉伸破坏演变,破裂程度增大并逐渐表现出岩爆倾向;声发射b值随加载时间增大经历了先上升、后波动、最后下降的演化阶段,呈逐渐减小趋势;类硬岩的临界破坏前兆点(b值)为0.68,声发射前兆信息的预警时序由大到小为累计振铃计数、累计能量、b值,具有良好的时效性和可靠性。研究成果对揭示硬质围岩体力学特征和破坏前兆信息预警提供一定参考。

     

    Abstract: For the purpose of clarifying the correlation between Acoustic Emission(AE) and rupture response characteristics and loading rate in the failure and instability of hard rocks, uniaxial compression tests and acoustic emission tests were conducted on hard rock-like material samples at different loading rates to analyze the characteristics of mechanical parameters, AE phenomena and rupture response characteristics of hard rock-like material, and to obtain the early warning information of the rock failure based on the information on AE parameters. The results show that the peak strength, elastic modulus and peak strain of hard rock-like material have the loading rate effect. The mechanical parameters generally increase exponentially with the increasing loading rate. The mechanical parameters grow rapidly at relatively low loading rates(0.10-0.15 kN/s), and are slightly slower at relatively high loading rates(0.20-0.25 kN/s). The AE parameters evolution shows a phased growth trend, and the maximum increase is positively correlated with the loading rate. As the loading rate increases, the AE amplitude and amplitude density gradually increase; the AE ringing counts change from low value-low frequency to high value-high frequency, and the AE energy from slone type to group type. The loading rate has a significant impact on rupture mode and fracture form. With the increase of the loading rate, the rock samples gradually evolve from shear failure to tensile-shear composite failure and tensile failure, and gradually shows an explosion tendency when the rupture degree increases. The b values of AE experience an evolution stage of first rising, then fluctuating and finally falling with the increase of the loading time, showing a gradual decreasing trend. The critical failure precursor(b value) is 0.68. The warning time sequence of AE precursor information is accumulated AE ringing counts, accumulated energy, b value from large to small, showing good timeliness and reliability. The research results provide a useful reference for revealing the mechanical characteristics and early warning of failure precursor information of hard surrounding rocks.

     

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