Study on the mechanism of large deformation induced by mudstone roof deterioration in water-weakened roadways and multi-level control

Le résumé fourni par la source

• CT/XRD/SEM reveal structural weakening characteristics of mudstone, sandstone and coal under water immersion. • Establishment of mechanical model for stability of high-low composite key blocks considering water weakening effects. • Analysis of stress field evolution in gob-side roadways under influences of dip angle/pillar width/water immersion parameters. • Proposed comprehensive control system: "rational pillar-gob drainage-chemical grouting-ultrafine cement reinforcement-timely shotcreting". To address the severe asymmetric large deformation in gob-side roadways under water immersion conditions in inclined coal seams, this study takes the return airway of the 110306 fully mechanized mining face in a coal mine as the engineering case. Through comprehensive methods including field monitoring, laboratory tests, theoretical calculations, and numerical simulations, the failure mechanisms and control technologies for asymmetric large deformation in water-softened roadways were systematically investigated. The main research findings include: (1) Experimental characterization: CT scanning, XRD diffraction, and SEM analysis were conducted to reveal the structural weakening characteristics of mudstone, sandstone, and coal under water immersion. (2) Mechanical modeling: A stability model for high-low composite key blocks in the immediate roof (water-weakened mudstone) and main roof (sandstone) was established, considering water-induced weakening effects. (3) Stress evolution analysis: The study elucidated the stress field evolution in gob-side roadways under the combined influence of multiple factors (coal seam dip angle, pillar width) and fundamental weakening parameters (water immersion range and degree). (4) Integrated control system: A comprehensive asymmetric control system was proposed, incorporating: ‘Rational pillar width design considering water weakening effects’ - ‘Comprehensive drainage through boreholes on the goaf side’ - ‘Chemical grouting injection in overlying mudstone to prevent water infiltration and argillization’ – ‘Ultra-fine cement grouting in pillar zones for surrounding rock reinforcement’ – ‘Timely shotcreting to prevent roof weathering’. The research provides both theoretical foundations and practical solutions for stability control of water-affected gob-side roadways in inclined coal seams.

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