rapid excavation and stability control of deep roadways for an underground coal mine with high production in inner mongolia

For large underground coal mines producing 10 million tons a year, rapid excavation and stability of deep roadways are pivotal to ensure sustainable, safe, and efficient production. This paper provides a case study of Hulusu Coal Mine in Inner Mongolia, where roadway excavation speed was insufficient to meet production needs. Moreover, deformation in the roofs of the roadways was severe. To achieve rapid excavation and control the stability of deep roadways, a new support system was proposed and constructed in a roadway at a depth of 640 m. The system consisted of long flexible bolts pretensioned to high levels and spaced at large intervals. Roadway excavation and construction of a support system were conducted simultaneously. Field measurements indicated that the new support system effectively controlled deformation and fracture development during excavation and mining. Maximum displacements of the roof during excavation and mining were 10 and 30 mm, respectively. The axial load on bolts surged during excavation as a result of slight deformations caused by excavation operations. This active response of the bolts is beneficial to the prevention of roof deformation during excavation and mining. During mining, fissures propagated up to only a depth of 1.4 m into the surrounding rock mass. The new support system formed a thick reinforced anchorage zone, which greatly improved the bearing capacity of the roof. Compared with the previous support system, the new system allowed the maximum excavation speed (31.5 m/day) to increase by 85.3%. This successful case provides a practical reference for similar roadway projects.