Mechanisms and control of large deformation in mudstone roof gob side entry of inclined coal seams with water softening

Le résumé fourni par la source

The gob-side entry in the inclined coal seams of the Songxinzhuang Coal Mine faces severe deformation under the influence of mudstone roofs water immersion-softened, and the conventional support is invalid. The main conclusions are as follows: (1) This study, through laboratory experiments both the macroscopic (water immersion tests) and microscopic (XRD and SEM) perspectives, reveals that the strength and bearing capacity of the mudstone in the immediate roof will reduce after water immersion softening, which is the root cause of the large deformation of the roadway from. (2) Through theoretical analysis established a stability evaluation system based on the softened friction angle ( φ ’) and the sliding stability coefficient ( K 1 ), and results showing that the key roof blocks above the gob-side entry become unstable under water-softened conditions. (3) Through simulations reveal the stress field distribution and evolution patterns of the surrounding rock under mudstone water immersion conditions. And results indicate that the mudstone under water-softened intensifies the expansion and coalescence of stress peak zones. When the softening depth exceeds 6–8 m, stress concentrations at the right rib increase rapidly and spread toward the roof and floor, forming a “stress envelope”. (4) Based on these findings, an asymmetric support strategy integrating grouting and drainage with a combined roof-bolt and steel-beam system was proposed. This approach effectively mitigates the impact of water immersion and enhances roadway stability. Field monitoring validated the effectiveness of this support system in controlling deformation and maintaining the integrity of the surrounding rock, providing critical guidance for managing similar challenges in inclined coal seams.

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