Numerical analysis of the influence of coal pillar size on auxiliary tunnel stability

It is very important to study the stability of the tunnel in the area affected by mining activities. In particular, the choice of coal pillar size has a direct influence on the stability of these tunnels. The authors of this study used the Flac3D program to model a mining face LC1 with various coal pillar sizes. The 220 m-long mining face known as LC1 has 20 degrees rock mass layers. The studied coal pillars are various widths at 5 m, 8 m, 10 m, 15 m, 20 m, and 30 m. The highest vertical stress and maximum horizontal stress are placed at different locations along the lower mining face (LC2), as shown by the results of the numerical simulation. The pressure distribution of the rock mass on the tunnel's top and the level of stress concentration on its two sides are asymmetrical for inclined seam conditions. The position of the maximum vertical tension is expected to change from the left hip to the side of the coal pillar as the coal pillar widens. This change essentially marks the system's transition from one stable state to another. Due to the rock mass's weak stability during this transition, the support must be strengthened in order to improve the rock stability.