贾蓬, 钱一锦, 王茵, 王琦伟. 基于声发射信息的热损伤花岗岩单轴压缩破裂机制及破裂前兆[J]. 工程科学学报, 2023, 45(12): 2129-2139. DOI: 10.13374/j.issn2095-9389.2022.10.21.006
引用本文: 贾蓬, 钱一锦, 王茵, 王琦伟. 基于声发射信息的热损伤花岗岩单轴压缩破裂机制及破裂前兆[J]. 工程科学学报, 2023, 45(12): 2129-2139. DOI: 10.13374/j.issn2095-9389.2022.10.21.006
JIA Peng, QIAN Yijin, WANG Yin, WANG Qiwei. Fracture mechanism and precursors of thermally damaged granite uniaxial compression based on acoustic emission information[J]. Chinese Journal of Engineering, 2023, 45(12): 2129-2139. DOI: 10.13374/j.issn2095-9389.2022.10.21.006
Citation: JIA Peng, QIAN Yijin, WANG Yin, WANG Qiwei. Fracture mechanism and precursors of thermally damaged granite uniaxial compression based on acoustic emission information[J]. Chinese Journal of Engineering, 2023, 45(12): 2129-2139. DOI: 10.13374/j.issn2095-9389.2022.10.21.006

基于声发射信息的热损伤花岗岩单轴压缩破裂机制及破裂前兆

Fracture mechanism and precursors of thermally damaged granite uniaxial compression based on acoustic emission information

  • 摘要: 为研究高温造成的热损伤对花岗岩在不同应力阶段声发射特征及破裂机制的影响,本文对25、200、400和600 ℃热损伤花岗岩开展了单轴压缩试验并进行了实时声发射监测,分析了不同应力阶段热损伤花岗岩峰值频率、上升时间/振幅-平均频率(RA-AF)数据分布特征以及能量集中度\rho 的分布规律. 结果表明:各温度热处理后花岗岩单轴压缩的应力阶段可以依据声发射发育特征分为:Ⅰ裂纹压密阶段、Ⅱ裂纹萌生及稳定发育阶段、Ⅲ裂纹非稳定发育阶段、Ⅳ峰后破坏阶段. 花岗岩的热损伤越严重,声发射峰值频率越早产生中、高频破裂信号,且主频带分布范围越宽,破坏时超高频信号越少. 各温度热损伤花岗岩声发射RA-AF数据分布特征可以表征各应力阶段产生的裂纹类型,热损伤花岗岩在压力作用下由压密至破坏过程中声发射RA-AF数据分布特征的变化说明剪切裂纹活动逐渐活跃,且热损伤温度越高,剪切裂纹越发育. 能量集中度曲线的稳定发育阶段与突降阶段之间的突变点可以作为花岗岩单轴压缩条件下的破坏前兆.

     

    Abstract: To determine the impact of high-temperature-induced thermal damage on the acoustic emission characteristics and fracture mechanism of granite during various stress stages, uniaxial compression tests and real-time acoustic emission monitoring of thermally damaged granite at 25, 200, 400, and 600 ℃ were performed. The peak frequencies of thermally damaged granites, the distribution characteristics of RA-AF (AE rise time/AE amplitude-AE average frequency) data, and the distribution patterns of energy concentration \rho at various loading stages were investigated. The results show that the stress stages of granite under uniaxial compression conditions after thermal damage at each temperature can be divided into the following stages: Stage Ⅰ corresponds to the crack compaction stage; Stage Ⅱ corresponds to the crack emergence and stable development stage; Stage Ⅲ corresponds to the crack unstable development stage; and Stage Ⅳ corresponds to the post-peak damage stage based on the acoustic emission development characteristics. Further, the more severe the thermal damage to the granite, the earlier the granite enters Stage II and the longer the duration of this stage. The acoustic emission peak frequency of thermally damaged granite at different temperatures exhibits a band distribution across four principal frequency regions. With increasing severity of thermal damage, the generation of medium- and high-frequency fracture signals occurs earlier, resulting in a wider distribution range of the primary frequency bands. In addition, there is a decrease in the occurrence of ultrahigh frequency signals during the failure stage. The distribution characteristics of the acoustic emission RA-AF data of the thermally damaged granite at different temperatures can provide insights into the cracking mechanism observed during different stress stages. Subsequently, Stage I generates a small amount of tensile and tension–shear cracks; Stage II generates mixed tension–shear cracks; Stage III generates tensile and mixed tension–shear cracks while shear cracks continue to develop and enlarge; and Stage IV generates numerous shear cracks. The thermally damaged granite is more likely to produce shear cracks under pressure. The higher the temperature of thermal damage, the more shear cracks develop. The curve of energy concentration based on acoustic emission data during uniaxial compression of granite contains three major stages: the initial irregular fluctuation, stable, and abrupt drop stages, which have obvious correspondence to stages I, II, and III, respectively. The abrupt change point between the stable and abrupt drop stages of the energy concentration curve can be used as a failure precursor for granite samples under uniaxial compression.

     

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