Seismic response and stability of underground rock caverns: a case study of Baihetan underground cavern complex

The seismic stability of the underground cavern complex, which houses the Baihetan hydropower plant in Yunnan Province, China, currently the world's 2nd largest underground rock cavern group, is studied in this article. A preliminary performance-based seismic assessment approach specified for underground rock caverns is firstly proposed. The seismic performance objectives are classified. Reference earthquake motions are specified with the determination of the seismic variables. Detailed dynamic response analyses (Method 2B) are conducted based on the parameters given by the cyclic dynamic loading tests with medium strain rate. The seismic response of acceleration, stress, displacement and failure zones are studied. In addition, the seismic spectrum characteristics are analysed with a newly introduced wavelet packet technique. The mechanism of the support measures for seismic stability is also discussed. The assessment for seismic performance of the underground cavern complex is obtained by integrating these results. Serviceability objective of the underground cavern complex under operating basis earthquake may be satisfied, and the safety objective be feasible but with the presence of the proposed reinforcement system. The seismic isolation design is preferred, yet not necessary. And if any seismic isolation design is to be adopted, the frequency absorption range of the isolation material is expected to be 1-4 Hz.