Strength Damage and Acoustic Emission Characteristics of Water-Bearing Coal Pillar Dam Samples from Shangwan Mine, China

• Published in: Energies (Basel) 2023-02, Vol.16 (4), p.1692
• Main Authors: Wu, Yang, Yao, Qiangling, Wu, Baoyang, Xie, Hongxin, Yu, Liqiang, Li, Yinghu, Wang, Lujun
• Format: Article
• Language: English
• Subjects: Acoustic emission; Acoustic emission testing; Acoustics; Analysis; Coal; Coal mines; Coal mining; Cycle time; Dam engineering; Dams; Drying; dry–wet cycles; Emission analysis; Energy dissipation; Environmental aspects; Failure mechanisms; Groundwater; Mechanical properties; Methods; Mines; Mining engineering; Moisture content; Research methodology; Reservoirs; Strain hardening; strength damage; Sustainability; Sustainable development; Water content; Water shortages; Wetting
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en16041692

Long-term erosion and repeated scouring of water significantly affect the technical properties of coals, which are the essential elements that must be considered in evaluating an underground reservoir coal column dam’s standing sustainability. In the paper, the coal pillar dam body of the 22 layers of coal in the Shangwan Coal Mine is studied (22 represents No. 2 coal seam), and the water content of this coal pillar dam body is simplified into two types of different water content and dry–wet cycle. Through acoustic emission detection technology and energy dissipation analysis method, the internal failure mechanism of coal water action is analyzed. This study revealed three findings. (1) The crest pressure, strain, and resilient modulus in the coal sample were inversely related to the water content along with the dry–wet cycle number, while the drying–wetting cycle process had a certain time effect on the failure to the sample. (2) As the moisture content and the dry–wet cycle times incremented, three features were shown: first, the breakage pattern is the mainly stretching fracture for the coal specimen; second, the number and absolute value of acoustic emission count peaks decrease; third, the RA-AF probability density plot (RA is the ratio of AE Risetime and Amplitude, and AF is the ratio of AE Count and Duration) corresponds more closely to the large-scale destruction characteristics for the coal samples. (3) A higher quantity of wet and dry cycles results in a smoother energy dissipation curve in the compacted and flexible phases of the crack, indicating that this energy is released earlier. The research results can be applied to the long-term sustainability assessment of the dams of coal columns for underground reservoirs and can also serve as valuable content to the excogitation of water-bearing coal column dams under similar engineering conditions.