Mechanism and validation of pressure relief and energy reduction of automatically formed roadway by roof cutting in deep coal mines

The mine pressure in deep mining is enormous, which can easily lead to coal bursts. At present, the method of automatically formed roadway (AFR) by roof cutting has been widely used in shallow buried coal mines. However, there is a lack of systemic research about the whole process of forming and reusing AFR in deep coal mines. Therefore, by analyzing the structural characteristics and stress distribution of AFR, the mechanism of pressure relief and energy reduction of AFR was revealed, which reduced the peak stress and energy of the roadways and the reserved coal pillar was cancelled. To verify the effect of pressure relief and energy reduction of AFR, the numerical comparison test of gob-side roadway driving and AFR was carried out. Two quantitative evaluation indexes of reducing rate of stress and energy were established, and the effect of pressure relief and energy reduction of AFR was verified. What’s more, the field results showed that AFR can effectively reduce the stress, micro-seismic energy and deformation of roadway. Compared with the method of gob-side roadway driving, the maximum stress, the maximum micro-seismic energy and the deformation of the roof using AFR decreased by 24.46%, 62.33% and 40.40%, respectively. Furthermore, the construction processes an engineering suggestions d of AFR were put forward. This paper provides an effective guidance of AFR in deep coal mines.