Mechanical model for controlling floor heave in deep roadways with U-shaped steel closed support

Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep; however, it is very difficult to control floor heave of roadways. In this paper, a U-shaped steel closed support with an inverted U-shaped steel arch in the floor is proposed as a method for improving the support effect of the surrounding rock during the process of floor heaving. This research established a mechanical model for the U-shaped steel closed support, and determined the reaction forces at the connection of a camber angle. Using the limit load method calculated the critical buckling load of the inverted U-shaped steel arch, and use of a strength check method tested the strength of the U-shaped steel material. A numerical simulation was conducted using the finite difference software FLAC3D. The simulation results show that the U-shaped steel closed support is able to control the floor heave of roadways, which is successfully used in the West 11-2 development roadway of the Zhuji Mine in the Huainan mining area in China. The cumulative floor heave over two years was less than 50 mm.