Abstract:

The concept of representative value of the dynamic stress concentration factor is proposed to describe the degree of dynamic stress concentration of underground openings under seismic loading. And the representative factor is employed to reflect the seismic response characteristic of underground openings. Based on explicit finite difference method, the relationship between five key factors: (1)acceleration amplitude of seismic wave, (2) overburden depth, (3) rock grade, (4) liner thickness and (5) concrete grade, and the representative factor has been investigated. It is shown that all these five factors appear approximate linear relationship with dynamic stress concentration factor. Accordingly, formulas of seismic safety assessment have been developed for both lined and unlined underground openings and a safety assessment method for underground engineering in rock under seismic loading has been proposed. The proposed assessment method is therewith applied to evaluate the safety of Xiluodu underground cavern groups subjected to Tangshan aftershock. It is demonstrated that the proposed method draws similar conclusions to Dowding-Rozen and Sharma-Judd’s methods. It also reveals that this method gives a relatively conservative assessment results.

Key words: seismic safety assessment method, Xiluodu hydropower plant, underground opening in rock, seismic response