Uncovering the progressive failure process of primary coal-rock mass specimens: Insights from energy evolution, acoustic emission crack patterns, and visual characterization

• Published in: International journal of rock mechanics and mining sciences (Oxford, England : 1997) England : 1997), 2024-06, Vol.178, p.105773, Article 105773
• Main Authors: Yu, Xiang, Zuo, Jianping, Mao, Lingtao, Xu, Xiaowei, Lei, Bo, Zhao, Shankun
• Format: Article
• Language: English
• Subjects: Acoustic emission; Chaotic bifurcation of energy; Coal-rock samples; Crack classification; Velocity tomography
• ISSN: 1365-1609
• DOI: 10.1016/j.ijrmms.2024.105773

The failure and instability of deep coal-rock mass structures, which are influenced by mining disturbances, are major contributors to disasters like rock bursts. This study involved conducting indoor experiments using uniaxial loading test and acoustic emission (AE) experiments on indigenous primary coal-rock mass (PCRM). We utilize chaotic bifurcation based on strain energy to characterize the progressive damage stages of PCRM, demonstrating the chaotic characteristics of energy evolution during the gradual destruction process. The degree of damage resulting from PCRM failure was evaluated by jointly applying P-wave velocity tomography and AE event localization. Additionally, the classification of crack patterns in PCRM was conducted using the RA-AF correlation analysis method. The segmentation boundaries of crack classification patterns were then redefined using the Gaussian mixture model (GMM) algorithm. The research findings indicate that the chaotic bifurcation model of strain energy classifies stress into four stages: the stable region (Ⅰ), the metastable region (Ⅱ), the bifurcation region (Ⅲ), and the chaotic region (Ⅳ). The presence of a low-velocity zone in P-waves may indicate crack accumulation and damage within the system. Additionally, areas with abnormal P-wave velocities exhibit numerous AE events. The crack classification patterns of the four stages undergo an evolution from predominantly tensile cracks to a mixture of tensile and shear cracks, and the GMM algorithm successfully identifies the optimal separation path for crack classification boundaries. We propose an adaptive kernel density estimation (AKDE) algorithm to quantify the spatial distribution of AE events, thus offering a visual representation of the damage patterns at various stages. •The new strain energy chaotic bifurcation model divides the progressive damage of PCRM into four stages.•Joint inversion of P-wave velocity tomography and AE event localization was employed to assess the extent of damage caused by PCRM failures.•The Gaussian mixture model better identifies the separation line paths for optimal RA-AF crack classification.•A new AKDE acoustic emission estimation algorithm for characterizing visual micro-cracks in PCRM.