Abstract:  Currently, there are problems such as lack of onsite monitoring data and single research method in giantspan flat caverns, which cause difficulties in analyzing the deformation characteristics and stability of caverns. Here, a case study is conducted on a giantspan cavern with horizontal stress as the main stress. Additionally, based on the geological conditions, insitu stress, and excavation sequence of the cavern, the settlement characteristics of a giantspan cavern arch are analyzed using onsite monitoring data analysis and threedimensional numerical calculations. The results reveal the following: (1) The overall settlement of the giantspan cavern is relatively small, with a maximum value of 22.8 mm, it is affected by geological conditions, ground stress, and structure, and its deformation has a certain degree of discreteness. (2) The dismantling sequence of the rock pillar in the giantspan cavern accounts for 40%~60% of the total settlement. (3) The deformation curve of the giantspan cavern during the excavation process presents the characteristics of a combination of step and zigzag, and its stabilization mechanism is a combination of the overall stability of stress control and the local stability of the structural plane control. (4) The excavation disturbance range of the vault of the giantspan cavern mainly exists in the shallow rock mass around the cavern, and the excavation disturbance range near the spandrel mainly exists in the shallow and middle rock mass around the cavern, and the excavation has a weak influence on the deep rock mass.

Key words: giant-span cavern, arch settlement, deformation characteristics, ground stress, structural surface, overall stability, local stability