AUTHOR=Zhang Leiming , Lai Xingping , Bai Rui 

TITLE=Study of the response characteristics of the water–force coupling action of hard coal bodies in steeply inclined coal seams

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 10 - 2022

YEAR=2023

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.1062738

DOI=10.3389/feart.2022.1062738

ISSN=2296-6463

ABSTRACT=To solve the problems related to the low recovery rate of coal resources and frequent dynamic disasters due to the low degree of fragmentation of hard top coal during the high stage fully mechanized top coal caving in steeply inclined coal seams, the study of the pre-blast weakening of hard top coal water-injection is especially important. With the application of rock mechanical test and numerical simulation, this study carries out mechanical properties testing on natural and water-saturated coal samples, investigates the effect of moisture on coal sample mechanical properties in meso-scale, and quantifies the degradation of coal samples under moisture due to mollification, as well as revealing the interaction between water and acoustic emission signal based on the statistics of acoustic emission count and energy; the numerical model is then established to analyze coal sample internal stress distribution features before and after water injection in macro-scale. Moreover, the detailed mitigating measures for top coal water-injection for engineering practice are designed. The results demonstrate that the mechanical properties of coal samples are significantly affected by moisture-inducted degradation. The failure degree and collapse degree of water-saturated samples are generally larger than those of natural samples; the higher the water content is, the smaller the acoustic emission count and energy of coal sample are, presenting a negative correlation. The internal stress of coal samples before and after water injection differ significantly. When subjected to water, top coal stress releases and transfers, and the peak value is significantly reduced. It is verified in macro and meso scales that top coal can be fully weakened under “water-force” coupling. The finding in this study is of practical significance for safe and efficient mining, and provides reference for presplit weakening of hard top coal during horizontal sublevel fully mechanized top coal caving in steeply inclined coal seams.