Experimental method and teaching design practice of shear-seepage coupling at the interface of gas-bearing coal-rock structure
[Objective]Faults and fractures are prevalent in coal seams and create zones that exhibit stress and gas anomalies and have a natural tendency toward instability owing to their"interface"physical structure characteristics.Geological structural zones become disaster-prone areas in coal mining.Shear slippage and gas flow at these structural interfaces during mining disturbances may play a dominant role in triggering coal and gas outbursts.Understanding the shear-seepage coupling characteristics at these interfaces is crucial for elucidating the mechanisms behind gas outbursts and for ensuring safe coal mining operations.[Methods]This study addresses frequent gas disaster issues at coal seam structural interfaces by conducting experiments on shear-seepage coupling systems involving gas-bearing coal-rock samples.This study primarily analyzed the shear mechanics of the coal-rock sample interfaces and the gas flow patterns.Using scanning electron microscopy and interface surface profile testing,the evolution of the physical structure characteristics during slippage was examined.A novel method for characterizing interface height was proposed to analyze the correlation between microscopic structural features and macroscopic shear mechanics,thereby clarifying the mechanism of interface slippage instability affecting coal and gas outbursts.[Results]The shear mechanical response at the coal-rock interface was primarily supported by the protuberances on the shear surface.During the shearing process,these protuberances undergo elastic deformation,shear wear destruction,and debris filling.At peak shear strength,protuberances experience substantial shear failure,resulting in a post-peak stress drop.Subsequent shear slippage processes lead to continuous local deformation and fracture of these protuberances,causing localized deformation damage on the shear surface and overall stick-slip instability.The study found that the peak stress drop and stick-slip stress drop increase with higher normal stress,while the frequency of stick-slip events decreases as normal stress increases.Stick-slip stress drops represent single self-locking failures of faults,reflecting the energy release process during each instability event.Increasing the normal stress enhances fault shear strength,allowing more strain energy accumulation and strengthening the self-locking ability of the structural interface.Inconsequently,fewer stick-slip events occur during shearing,but larger stress drops release more energy when rupture instability thresholds are reached.Microscale analysis of the fault shear surface texture revealed that higher normal stresses lead to more pronounced damage to the protuberances on the shear surface,resulting in lower post-shear protuberance heights and a more uniform distribution.The greater extent of damage under high normal stresses means that the shear surface bears greater shear stress and releases more energy,leading to fewer stick-slip events but larger stick-slip stress drops.This dynamic illustrates the critical balance between fault-locking capacity,energy accumulation,and release during geological disturbances.[Conclusions]The results showed that the shear mechanical response at coal-rock interfaces is primarily supported by protuberances on the shear surfaces.Higher peak strengths of these protuberances correspond to greater peak shear strengths and more substantial stick-slip stress drops,although the frequency of stick-slip events decreases.Under controlled conditions,increasing normal stress enhances the shear strength of the weak-plane structural interfaces in the coal-rock allowing more strain energy to accumulate.During shearing,fewer stick-slip events occur,however,when the threshold for rupture instability is reached,a significant stress drop occurs,releasing considerable energy.The findings provide theoretical guidance for exploring the shear mechanics of gas-bearing coal-rock interfaces.They offer insights into the mechanisms behind dynamic instability-induced disasters at these interfaces.This paper combines experimental systems,methods,result analysis,and physical characterization to bridge the gap between research theories and practical technical challenges.By addressing these aspects through experimental content,the study significantly contributes to the integration of industry,academia,and research.Moreover,it enhances the collaboration between research and teaching.
structural interfacegasshear-seepage couplinggas power disaster
万方数据
维普
