Abstract: There is no relevant normative guidance for the construction deformation control of the super-large-span flat underground cavern with a span greater than 50 m. Therefore, the theoretical analysis and numerical simulation methods are used to study the deformation control standards for large-span caverns based on an actual project. To assess the stability of a large-span cavern, the surrounding rock strain is used as a rock mass strength index. The settlement-span ratio is proposed as the deformation control standard, and a correlation between cavern crown settlement and rock mass ultimate strain ε is proposed. Furthermore, the deformation control standards applicable to each excavation stage are proposed, and the classification management method for deformation control standards is developed. The results show the following: (1) The allowable settlement deformation of a large-span cavern is related to the geometry of the cavern and the strength characteristics of surrounding rocks. (2) Regarding the excavation scheme of partial excavation and reserved rock pillar for the case study of the large-span cavern, the deformation of the cavern mainly occurs in the large-span cavern stage.

Key words: super-large-span flat underground cavern, rise-span ratio, ultimate strain, deformation control standards, numerical simulation