Abstract: The axial arrangement of underground caverns is crucial and complicated in complex rock structures. This article explores the optimization selection of underground caverns axis in a pumped storage power station influenced by complex rock structures and geo-stresses. By employing a multi joint constitutive model for efficient consideration of multiple rock mass structures, preliminary and refined optimization of the cavern axis were conducted. The excavation response of surrounding rock is presented as the evaluation index, an optimization method for tunnel group axis direction was proposed. Results show that two dominant structural faces significantly affect the cavern group’s excavation response. Under advantageous structural planes control, differences exist in the caverns’ deformation and plastic zone distribution patterns and quantities. Under structural planes control, the cavern group’s maximum deformation occurs on the upstream side wall. Comparing the proposed 290°, 0°, and 330° axis directions, 0° is better than 290° based on deformation and plastic zone. Considering the near NE direction of water flow, current 290° axis is reasonable. Within 285°-295°, axial direction has little impact on cavity excavation deformation and plastic zone. Quantitative comparison indicates the 285° direction is optimal under current conditions. This study offers references for similar project construction and research.

Key words: Underground Caverns, Axis Direction, Rock Mass Structure, In Situ Stress, Optimal Design