Comparison of the macroscopical stress field distribution characteristics between a novel non-pillar mining technique and two other current methods

Abstract

Recently, an original innovative non-pillar coal mining technology was developed and widely implemented in China’s coal production based on this background. To explore the difference of stress field distributions between a novel non-pillar mining technique and two other current methods, different numerical models, that is, mining with gob-side entry retained by filling (GERFM), mining with roof cutting and pressure relief (RCPRM), and non-coal pillar mining with roadway formed automatically (RFANM), had been built based on the first industrial test of RFANM. The difference of the stress field distributions in those three types of mining patterns was studied and analyzed. The results showed that in front of the mining face, the influence of gob-side entry retaining method on stress distribution had a limited range. Due to the impact of roof cutting, the vertical stress of RCPRM was the minimum within the range of 0–10 m from the roadway, and it was the maximum within the range of 10–80 m. In the mining pattern of GERFM and RCPRM, the abutment stress was highly concentrated around the gate entry, and the stress-concentrated position of RCPRM was further than GERFM under the influence of roof cutting. However, there was no stress concentration in RFANM because the gate entry was canceled in this new mining pattern. At the side of mining face, the stress-concentrated position of GERFM was always located in the coal seam and was close to the roadway, whereas the stress-concentrated position of RFANM and RCPRM was located in the top layer which was deeper and higher than GERFM and was far away from the roadway. While the roadway was stable, the relationship between the peak value of the surrounding rock stress was GERFM > RCPRM and RFANM. According to the above laws, it was obtained that canceling early excavation was helpful to reduce the advance pressure in front of the working face, and roof cutting could cause the stress concentration zone to move away from the roadway. Thus, the stress of surrounding rock near the roadway was reduced, which was more beneficial to ensure the stability of the roadway.