True triaxial failure behavior and structure-material synergistic failure mechanism of coal-rock composites
ZUO Jianping
XU Chengyi
ZHAN Shuaifei
MA Zongyu
YU Xiang
SUN Yunjiang
Abstract：The mechanical behavior of deep-buried coal-rock masses under multi-field coupling effects exhibits greater complexity compared to shallow formations,rendering the investigation of failure mechanisms in coal-rock composite specimens under true triaxial conditions crucial for understanding disaster-inducing mechanisms in deep coal mines.This study conducted true triaxial loading experiments on cubic coal-rock composite specimens sampled from Tashan Coal Mine using a self-developed multi-dimensional simulation system for complex deep geological conditions.The experiments examined specimens with structural plane inclinations ranging from 0° to 45° under various simulated confining pressures,while simultaneously monitoring a-coustic emission(AE)characteristics throughout the loading process.Results demonstrate that both horizontal principal stress magnitude and structural plane inclination significantly in-fluence the overall failure behavior and strength of coal-rock composites.As inclination increa-ses from 0° to 45°,the specimen strength progressively decreases across all confining pressure conditions.Specimens with 0° and 15° inclinations predominantly fail through coal matrix frac-turing,whereas those with 30° and 45° inclinations exhibit slip-shear failure concentrated along interfacial structural planes.The AE signals during failure evolution can be categorized into three distinct stages:initial low-frequency activity during compaction,quiescent period during geostatic stress maintenance,and high-frequency activity preceding failure instability.Numeri-cal simulations employing PFC3D software replicated true triaxial tests on composite specimens with seven inclination angles under five burial depth conditions,further validating the influence of inclination and depth on failure patterns.Theoretical analysis reveals that the failure mecha-nism of inclined coal-rock composites is collaboratively controlled by material properties and structural characteristics.When structural plane inclination remains below a critical threshold,failure manifests as structure-dominated with material-assisted behavior;conversely,material-dominated failure with structural assistance occurs beyond this threshold.Notably,increasing burial depth gradually diminishes structural control dominance,potentially reversing the con-trol hierarchy.Experimental,theoretical,and numerical findings collectively verify the struc-ture-material synergistic control mechanism governing coal-rock composite failure.This re-search provides theoretical foundations for understanding deep coal-rock failure mechanisms and optimizing surrounding rock stability control strategies.
Keywords：true triaxial testingcoal-rock cubic assemblagessynergistic control of structure and materialsoverall failure behaviors of deep coal and rock masses
Publication Date：2025-03-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：17( 287-303 )