The mining pressure in mixed workface using a gangue backfilling and caving method

In order to reveal mining pressure in the workface using a gangue backfilling method and a caving method in Pingdingshan No. 12 coal mine, this paper establishes a numerical analysis model for different advance lengths of workface based on geological conditions. By the analysis of numerical models and field measurements, the following conclusions about mining pressure behavior in the mixed workface were drawn. (1) As the mixing face advances, its goaf is continuously compacted. Therefore, the vertical stress in the roof of the mixed workface increases gradually. (2) Because the gangue has a certain supporting effect on the roof, the peak value of abutment stress in the gangue backfilling section is less than that in the caving section, while the roof vertical stress in the goaf of the backfilling section is greater than in that of the caving section. (3) Because roof break and movement are different in the gangue backfilling section and caving section of the mixed workface, a sudden increase of vertical stress in the transition section appears. (4) Through the analysis of the working resistance of the hydraulic support and the advance stress of the coal wall in the mixed workface, the supporting role of gangue for the goaf roof and the abrupt increase of vertical stress in the transition section are verified. (5) The mining pressure of the mixed workface shows that the mining management of the caving and transition sections should be strengthened.