Research and discussion on dynamic mechanics of surrounding rock in green mining of residual coal resources and function improvement of goaf

FENG Guorui; WEN Xiaoze; GUO Jun; HAN Lei; BAI Jinwen; QIAN Ruipeng; WANG Kai; ZHANG Xu; JIN Jiang; ZHANG Xiaorong

doi:10.26940/j.cnki.10-1912/TD.2504

Abstract：Residual coal resources are abundant and widely distributed,possessing dual value as high-quality energy and strategic underground space.Based on the origins,propagation attenuation,and characteristics of static loading associated with disturbance stress waves during upward mining and underground space utilization in coal mine goafs,this study pro-poses the scientific issue of"low-frequency dynamic disturbance coupled with static pre-stress."A theoretical framework of disturbed rock mechanics was developed to support the synergistic system of residual coal recovery and underground space development.A multi-field coupling servo testing system was independently designed,capable of applying water-gas-temperature conditions along with static and dynamic loads.Drawing on prior studies,this research systematic-ally investigates the dynamic mechanical responses of coal and rock materials under low-frequency disturbances,includ-ing tension,compression,and shear behaviors.The relationship between the number of disturbance cycles and amplitude prior to instability in high-stress coal and rock was quantitatively characterized.Strength degradation behaviors under vari-ous static pre-stress levels were evaluated for sandstone,coal,and backfill materials.Predictive criteria were proposed for the pre-failure identification of high-stress coal-rock systems under disturbance,revealing intrinsic mechanisms linking strength degradation to microcrack evolution.A damage variable and strength criterion incorporating low-frequency dis-turbance effects were derived.Findings indicate that the influence of excavation-induced disturbance must be fully con-sidered in feasibility assessments,stability evaluations,and dynamic instability prevention during residual coal mining.These results provide theoretical guidance and decision support for the safe and efficient development of residual coal and underground resources in mined-out areas.However,challenges remain in achieving safe and green recovery of residual coal and the scientific utilization of goaf spaces,particularly under the compounded risks of water accumulation,gas buildup,dynamic pressure,and spontaneous combustion.The practical application of disturbed rock mechanics in the"re-sidual coal-space development"framework still faces several technical bottlenecks:The dynamic mechanical behavior of coal and rock under complex water-gas-thermal conditions remains unclear;The amplification effect of existing fractures in disturbed coal-rock mass under multiple mining disturbances lacks quantitative characterization;The stability and long-term operation of novel carbon storage/fixing backfill materials and their constructed spaces require further study;The li-thological heterogeneity of sedimentary rocks hinders the development of universal dynamic mechanical models and con-stitutive relationships.To overcome these challenges,it is essential to advance the engineering translation of disturbed rock mechanics theory within the regulatory framework of coal mine safety.This will enable breakthroughs in green,low-car-bon utilization of residual coal resources and the empowered transformation of goaf space,supporting the development and implementation of critical technologies for high-recovery,safe,and sustainable mining of difficult-to-extract coal resources.