Abstract: To smoothly connect the precast internal structure and the shield segments of an electric power tunnel, a novel fully-precast internal diaphragm structural design draft based on the grouting rubber capsule is proposed. This structure can eliminate the problems in the existing plans. The construction site Beijing is located at the region with seismic precautionary intensity of eight degree, the seismic safety is a critical factor for selecting structural design drafts. Thus, it is necessary to examine the seismic responses of the novel structure and their differences with alternative structural plans. Herein, a three-dimensional nonlinear site-tunnel-internal structure finite element model is constructed based on the proposed novel design draft, the postgrouting mortar and the castinplace design drafts. The seismic analyses are conducted using the integrated response displacement method. The structural deformation, connection region deformation, and internal force responses are compared. Results reveal the followings: (1) The deformation of the internal diaphragm structure is small under infrequent seismic. The stable structure can normally transfer the internal force. Moreover, the flexible rubber capsules arranged between the precast bottom diaphragms and the segments deform under the seismic effect in both radial and circumferential directions of the tunnel, drastically reducing the axial and shear force of the internal structure. (2) For the post-grouting mortar design draft, the contact shear stress concentrates at regions near the circumferential seam. (3) The seismic safety of the novel structural design draft outperforms the two traditional design drafts. In addition, the grouting capsules are dry connections with rapid construction features, the applicable potential of the proposed novel design draft is great.

Key words: precast internal structure, seismic analysis, electric power tunnel, grouting capsule, precast diaphragm structure