Identification of the Rock Pressure when Excavation Tunnels Underneath the 790 Open-Pit Mine Edge in the Mong Duong Coal Mine, Vietnam

Abstract

Studying and identification rock pressure when excavation tunnels are very necessary. Calculating the rock pressure will help us to choose the suitable type of support, thereby building a reasonable support plan. The Mong Duong Coal Mine is one of the coal mines in Quang Ninh coalfield with part of its reserves or coal seams located under the edge of the open-pit mine that has ended exploitation. So, it is very difficult and complicated to excavate and support, as well as calculate the rock pressure for the tunnels arranged under this area. If the excavation and support methods are not good, potential unsafe risks may occur. One of the most dangerous phenomena may occur, that is the phenomenon of sudden inrush into the tunnel. In this paper, the numerical simulation method was used. On the basis of Phase2 software and geological conditions of the Mong Duong Coal Mine, the authors established a simulation model to identify the rock pressure acting on the tunnels that are located underneath the open-pit mine edge area. Through the actual study at Mong Duong Coal Mine, the authors calculated the rock pressure when excavation the tunnels underneath the 790 open-pit mine edge of the Seam L7 at West Side at -50 level. The 790 open-pit mine is located on the longwall in the Seam L7. The findings of the study serve as the foundation for the practical application at the Mong Duong Coal Mine. On the basis of calculating the rock pressure acting on the tunnels at the coal Seam L7, from which the tunnel support plan has been developed. This research method will also serve as a basis for other mines with similar geological conditions in Quang Ninh coalfield to consider and apply.