Abstract: To explore various conditions that affect the stability of shallow embedded caverns, a case history of a very large cavern in Xiamen is presented in this paper. The conditions examined are excavation, structural loads, seismic loads, and their combinations. The on-site geological surveys and data analysis provided the necessary mechanical parameters for simulations. The 3DEC simulations analyzed how the surrounding rock deforms and fails under these conditions. The results show the following: (1) The impact of stability of the embedded caverns, from strongest to weakest, is: combined structural and seismic loads, seismic action, excavation, and structural loads. (2) The cavern often experiences shear failures at the arch toe and crest of side tunnels, while tensile failures are rare and scattered. (3) Greater excavation depth reduces stability, and side tunnel excavation worsens the deformation. Structural load mainly affects the cavern’s sides. Changes in seismic force direction don’t destabilize the cavern, but seismic load in the Z-direction impacts stability the most. (4) When seismic force is in the X-direction, structural load can enhance stability. In other directions, it increases deformation.

Key words: Underground Engineering, 3DEC, Shallow-Embedded Cavern, Multi-Condition Impact Mechanism