Reasonable width and control technique of segment coal pillar with high-intensity fully-mechanized caving mining

In order to investigate the problem of reasonable pillar width with high-intensity fully mechanized caving mining,taking Yangchangwan coal mine as an engineering background,the breakage structural model of lateral main roof of fully-mechanized caving mining was established and the width of low stress field and its influencing factors were derived. Also,the stress and deformation evolution laws of surrounding rock with different widths of coal pillar during the excavation and mining were analyzed by using FLAC3D . The results show that ① Due to large-size in working face, high advance speed and long caving interval,the width of internal stress field in high-intensity mining face is larger than that in ordinary coalface. ② The factors such as multiple times mining influences,main roof fracture and large cross-section should be considered in determining the reasonable width of segment pillar. Combining with geological conditions of the test site,the width of internal stress field is calculated to be 6. 31-7. 58 m and the reasonable pillar width is 9-14 m. ③ The strata structure is activated again during the retreat of mining face,which deteriorates the de- formation and failure of surrounding rock. The overall displacement of surrounding rock is smaller when the pillar width is 10-14 m and the reasonable pillar width is determined as 10 m by considering comprehensively. ④ The gob-side entry with small pillar may induce large-area broken,large deformation of coal pillar sides and asymmetric subsidence of roof. To achieve the stability control to similar roadway,the key control strategy is to reinforce pillar and roof. After- ward,the asymmetric control technology of surrounding rock was proposed and applied in field test. The surrounding rock deformation of gob-side entry was effectively controlled.