Earthquake and Underground Powerhouse: On the Aseismic Issues of Baihetan Underground Cavern Complex

A hydropower plant is usually the major electricity supplier in the region, the failure of underground powerhouse in an earthquake may cause not only the damage to itself, but also secondary disasters to the region in a way of an electricity outage Seismic stability of these underground complexes is required to be seriously addressed. The underground cavern complex of the Baihetan hydropower plant in Yunnan Province, China, is currently the world's largest underground rock cavern group under construction. Aseismic issues of the underground cavern complex are discussed in this paper. On the basis of this research, seismic variables of the Baihetan project are firstly determined for Design Basis Earthquake and Safety Evaluation Earthquake. The artificial seismic motions for the dynamic analyses are simulated. Two alternative scheme of layout plans of the underground cavern complex are studied, with full 3-D elasto-plastic dynamic response analyses based on the parameters given by the cyclic dynamic loading tests with medium strain rate. The seismic response of seismic displacement and failure zones of each scheme are studied, respectively. A performance verification of the supporting measures during earthquake is also discussed. The results indicate that in spite a wider powerhouse cavern, the scheme "A" which involves a gallery-shaped surge chamber is more stabilized during an earthquake than the scheme "B" whom with barrel-shaped surge chambers. The underground cavern complex with scheme "B" is relatively stable under Design Basis Earthquake and Safety Evaluation Earthquake, despite a minor damage of the surrounding rock. And the implementation of the proposed support system may further guaranteed a safe state of the underground cavern complex in earthquake events.