Exploration and Numerical Analysis of Failure Characteristic of Coal Pillar Under Great Mining Height Longwall Influence

Great mining height longwall face (GMHLW) is widely used in China, with the extraction height increasing to be 7.0 m. This technology is different from normal mining height due to the extra large boundary of caved roof strata. And it leads to strong abutment loading. To comprehend the failure of traditional coal pillar under the strong abutment loading, a comprehensive approach for revealing damage characteristic of coal pillar was proposed by analyzing the damage zone distribution. First, a sensitive instruments named ‘bore hole camera exploration device’ (BCED) was used to explore damage zone of coal pillar at Bayangaole Coal Mine, China, a typical GMHLW. Second, in order to back-analyze the failure mechanisms, a numerical model of 311101 panel was built using FLAC3D. To improve the accuracy of the numerical model, the strain-hardening gob and strain-softening pillar materials were meticulously calibrated. Results show that mining disturbance induced by GMHLW had great impact on coal pillar stability. Large fractured zone (LFZ) and small fractured zone (SFZ), with different scope, were found at different position in coal pillar. The results of the validated model indicate that LFZ and SFZ were formed by tension-shear failure and shear failure, respectively, during the longwall face approaching.