Numerical modeling for further understanding of roadway junction stability behaviour at deep underground

The review and numerical analysis had been conducted further understand the deformation and failure beahviour of roadway junctions, associated with the different geometrical characteristics, various depth of cover, different mechanical properties around the junction and different construction sequences as well as different construction advances during the roadway junction construction. The results confirme that the simple underground structure is more stable than complicated structures, and comparing with different geometrical shapes of the two-dimensional roadway junctions, the most unstable one is the four way cross junction, which is the most commonly used in coal mines. On the other hand, the stability of the junction is not linearly related to the depth of cover, the significant effect only occurred when the depth of cover reached to 1 000 m. Also, with gradual degradation of rock mass, the deformation and failure around the junction increased significantly and nonlinearly. The modeling also conductes on the construction sequence for the junction, it is suggested that, during the junction construction, all the additional roadway should be constructed with the direction of moving away from, rather than forward to the junction. Finally, the construction advance is also considered for the junction development. It is suggested that when the construction is carried out around the junction, a small excavation advance, such as 1 m or 2 m is adopted for keeping small interruption on the existed roadway or junction.