Preliminary analysis on excavation stability of Beishan Underground Research Laboratory

According to construction requirements of the first underground research laboratory (URL) for high-level radioactive waste (HLW) disposal in China, preliminary analysis on the excavation stability was carried out. Based on in-situ stress conditions and preliminary design of the URL, excavation induced stresses were revealed by numerical simulation. Then, through coordinate conversion, the excavation induced stresses were converted into local coordinate system perpendicular to the tunnel. Finally, an analytical method that compares rock strength with stress conditions is used to evaluate the excavation stability of surrounding rock in the local coordinate system. Results of this study show that: due to the high strength of Beishan granite and low level of the regional in-situ stress, the Beishan URL is highly likely to remain stable after excavation, the surrounding rock can hardly be destroyed by both tensile and compressive stress. Relatively unstable parts of the URL are the bottom of the shaft, rotation parts of the -560m-platform and some corners. These parts should be paid attention to in the future excavation process.