ABSTRACT
The study entry is in the Gaocheng coal mine in Henan Province of China. The thickness of the No. 21 coal seam is 4.8 m and the average depth is about 450 m, the dip angle of coal seam is 8°–13°. The roof is in sliding structural zone, which is extremely broken, and the floor is soft sandy mudstone. It belongs to typical three-soft coal seam. The entry size is width 6.0 m and height 3.4 m. The mechanical parameters of coal and rock are shown in Table 1. The compressive strengths are 0.92-17.0 MPa, water softening coefficients are 0.24-0.36, and the elastic modulus are 33.0-413.8 MPa. It is clear that the surrounding rock is typical soft rock.
