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Application of the numerical method to analyze the effect of cross-sectional type in stabilizing the coal mine tunnel

For the coal mine tunnel, each type of cross-section of the tunnel will cause different laws of mechanical change in the rock mass around the tunnel. This difference is expressed through quantities such as displacement, stress, the damage zones within rock mass, etc.. It is completely unreasonable to adopt an independent mechanical parameter to evaluate the selection of the most optimal shape for the tunnel. To simulate the tunnel excavation process with different types of cross-section shapes in the same geological conditions, the software FLAC3D was employed. The data extracted from numerical simulation including displacement, stress field, plastic deformation area, the thickness of plastic deformation zone at the top, side, and bottom of the tunnel are evaluated. The type of section shape with the highest score will be evaluated as the most optimal one. The present case study shows that the type of cross-sectional shape of the straight wall with curved arch and deviated trapezoid got the highest scores of 36 points and 30 points, respectively. Therefore, the type of cross-sectional shape of the straight wall with curved arch and deviated trapezoid should be used. This shape choice will be the most optimal, and beneficial to the stability of the tunnel both during excavation and production progress.