ABSTRACT
The major concern over large underground silo-shaped caverns, consisted of domes and body shafts, is to select the proper excavation method because they are excavated sequentially by subdividing the large cross section considering safety, constructability and stability of working face. In this study, the excavation method and behavior characteristics of a large dome-shaped cavern, which is the upper part of an underground silo, were evaluated by 3-D numerical analyses in which each excavation sequence was simulated along with 3-D geometry. Bench type and pie type were finally proposed as possible excavation methods and compared each other in terms of construction sequence, support system, constructability, and stability, etc. The results showed that the pie type excavation sequence is more applicable than that of the bench type excavation. In the pie type excavation sequence less stress concentration was observed compared to the bench type excavation sequence. The orders of tunnel displacement and shotcrete stress were also comparatively small. In addition, extensive 3-D numerical analyses were performed considering full excavation modeling for the dome and body shaft of a silo. The results showed that construction with the proposed excavation method was safe and feasible.
