Study on mechanism of strong pressure behaviors in working face under residual coal pillars

Taking the 31106 working face of Huoluowan Coal Mine in Shendong Coalfield as the background, the stability of the combined bearing capacity of the coal pillar group under the overlying strata load transfer was analyzed, and the mechanism of strong mining pressure in the process of barrier coal pillar entering the room-pillars was explored using a similar material simulation method. The results show that during the period of the lower working face out of the barrier coal pillar, the width of the barrier coal pillar was gradually reduced due to the periodic collapse of the interlayer rock stratum. The abutment pressure resulted in the dynamic bearing of the combination of the barrier coal pillar and room-pillars. When the barrier coal pillar is reduced to 10 m and does not reach the critical instability width, the load transfer causes the load of the front 1# room-pillar from 5.28 MPa to 7.58 MPa and finally to be instable. After the instability of the 1# room-pillar, the load above is transferred to the adjacent coal pillars, causing the 2#, 3# and 4# room-pillars to lose stability from one by another. After the upper hard rock layer loses support, a long hanging roof of 58 m was formed in the room mining area due to the advanced fracture control. The hanging roof controlled the upper rock layer to transfer load downward through the barrier coal pillar. After the 5m out of the concentrated coal pillar, the roof was cut off to produce intense shock disturbance, and the stress increased rapidly from 4 kPa to 33. 6 kPa, with an increase of up to 740%, resulting in the manifestation of strong mining pressure in the lower working face. When the 31106 working face is mined under the upper coal pillar group, the roof blasting breaking or hydraulic fracturing roof cutting measures should be taken in advance to control the strong mine pressure disaster. © 2023 China University of Mining and Technology. All rights reserved.