The investigation of micro-crack generation in cementitious mine seals via temperature and strain analysis

Abstract

Mine seals are employed in underground coal mines to effectively isolate abandoned areas from active workings. The seals are engineered to prevent air movement and endure dynamic pressure events resulting from methane explosions. Mine seals are made from cementitious materials and undergo a curing process that involves an exothermic reaction known as hydration. The presence of moisture (hydration) may result in the mixture contracting, which could subsequently lead to cracking during the early phases of the curing process. Cracks in the seal can influence the performance and structural stability. This study examines the formation of micro-cracks in cementitious mine seals throughout the curing process by evaluating temperature and strain data collected from thermocouples and strain gauges that were installed during the pouring phase. The samples for the mine seal were prepared using two distinct mixtures: traditional concrete and pumpable products sourced from conventional suppliers. Heat evolution curves were produced for each sampling location corresponding to the three samples. The samples of Mixture A and B, prepared according to specifications, exhibited the anticipated heat evolution curves, with the maximum temperature occurring at the center of the samples. In contrast to the other mixtures, the samples of mixture C, which were prepared outside of the specified parameters, exhibited the highest temperature at the bottom of the sample. The strain measurements showed a correlation with temperature readings, indicating that mixtures A and B exhibited the highest strain at the center of the sample, while mixture C demonstrated the greatest strain at the bottom of the sample. The examination of the gathered data reveals a significant likelihood of micro-cracks forming in each of the samples.