Fracture behavior and micro-mechanism of limestone under acidic wastewater circulation from coal mines
YANG Xiao1, WANG Qianlong1, LIAO Jianxing1, 2*, WANG Tongbiao2, XIE Yachen3, 4
(1. College of Civil Engineering, Guizhou University, Guiyang, Guizhou 550025, China; 2. Guizhou Coal Mine Design and Research Institute Co., Ltd., Guiyang, Guizhou 550025, China; 3. College of Water Resources and Hydropower, Sichuan University, Chengdu, Sichuan 610065, China; 4. State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering, Sichuan University, Chengdu, Sichuan 610225, China)
Abstract：Acidic wastewater circulation from coal mines leads to the degradation of surrounding rock strength, which is a key factor contributing to the long-term stability failure of closed coal mines. Currently, there is a substantial amount of research on the fracture behavior and microscopic mechanisms of limestone under single-factor conditions. However, the relevant mechanisms under the combined influence of an acidic environment and dry-wet cycles still require further investigation. To explore the fracture behavior and microscopic mechanisms of limestone under acidic wastewater circulation, this study employed Brazilian splitting tests in conjunction with acoustic emission and digital image correlation techniques to analyze the effects on tensile strength, fracture characteristics, and crack propagation. Nuclear magnetic resonance and scanning electron microscopy was utilized to reveal mineral corrosion patterns and microscopic pore responses. The results indicate that: (1) with increasing circulation cycles, the tensile strength of limestone decreases significantly, tensile crack propagation becomes more pronounced, and the number of surface cracks increases during the fracture stage; (2) acidic wastewater circulation reduces acoustic emission (AE) ringing counts and high-energy events during failure, while both the a- and b-values derived from AE event statistics increase; (3) at the microscopic level, calcite dissolution reduces the surface calcium (Ca) content of limestone. Concurrently, due to the influence of metal ions in the acidic wastewater, the surface contents of iron (Fe) and magnesium (Mg) elements increase. The combined action of acidic wastewater and dry-wet cycles exacerbates internal microstructural damage in limestone, promoting pore evolution from micropores to mesopores and macropores, ultimately resulting in the deterioration of tensile properties. This study provides valuable insights into the fracture behavior and microscopic mechanisms of limestone under acidic wastewater circulation, offering a reference for understanding the degradation processes of related underground structures.
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2026, Vol. 45 
