Research on the Influence of Waste Dump Height on the Internal Forces of Steel Roadway Supports: A Case Study in Mong Duong Mine, Quang Ninh, Vietnam

Currently, the Mong Duong Coal Mine is extracting coal seams located beneath surface waste dumps. Roadways beneath these dumps exhibit phenomena such as subsidence, squeezing, and deformation of the support structures shortly after being put into operation. These phenomena are hypothesized to be caused by artificial pressure generated by the surface waste dump above. This article clarifies the influence of the waste dumping height on the internal forces of the steel support structures for both circular and U-shaped (straight wall and semicircular arch) roadways located beneath waste dumps under Mong Duong coal mine conditions. Numerical simulation using Phase2 software was employed, based on the geological conditions of cross-section A-A through the central area of the Mong Duong coal mine. The research simulated model was constructed with dimensions of 780 m (width) x 645 m (height). The circular roadway has a diameter of 5 m, while the U-shaped roadway has dimensions of 5 x 5 m; the surveyed roadways are located at a depth of -355 m within a siltstone rock mass. The study cases varied the waste dumping height at 0 m, 50 m, 100 m, 150 m, 200 m, and 217 m. The results indicate that the waste dumping height significantly influences the internal force values in the support structures for both circular and U-shaped roadways. As the dumping height increases, both the moment and normal force in the support structures of these two roadway types increases according to a clear pattern.