Research on excavation and support of underground caverns for Akto Pumped Storage Power Station

To optimize the support design for underground cavern excavation and address potential issues of inadequate support or excessive conservatism caused by traditional rock mass classification methods, we studied rock mass classification and Block theory, and elaborated on the design approach for cavern excavation support and proposes reinforcement solutions and recommendations based on Akto Pumped Storage Power Station project. The research indicated that for surrounding rock support, type Ⅲ rock primarily employed systematic bolt support, type Ⅱ rock may implement appropriately simplified support based on type Ⅲ standards, while type Ⅳ rock necessitates reinforced support including steel arch frames, with additional pre-support when required. The systematic support framework was determined by rock classification ("area-based" approach), while local reinforcement ("point-specific" measures) follows Block theory principles. This established a comprehensive underground excavation support design methodology prioritizing rock classification alongside block analysis. The findings can provide a reference for excavation support design during construction.