Design of the dome shape of complicated huge cylindrical surge chamber in Baihetan hydropower station

Abstract

Baihetan hydropower station located at lower reaches of Jinsha River in China, the hydropower station is characterized by its large scale and complicated layout. Four cylindrical throttled surge chambers sit in each bank with their heights about 100 m, and the diameters 43 to 48 m. The surrounding rock of the dome is affected by high in-situ stress, interlayer dislocation zone and columnar joints. The geological conditions are extremely complex and the stability of the surrounding rock is prominent. The numerical simulation method is used to build the calculation model of the dome with different shapes, and the excavation response characteristics of the domes are compared to determine the optimal shape. Research results: (1) The domes of the 1#∼3#, 5#, 6# surge chamber are mainly affected by the initial in-situ stress and surrounding rock lithology. The semi-circular shape is beneficial to improve the smooth transition of surrounding rock stress at the crown and spandrel. (2) The interlayer dislocation zone C4 and C5 jointly affect the dome of the 7# surge chamber. The semi-circular scheme can be used to control the relaxation deformation of the surrounding rock. (3) The streamlined scheme of the 8# surge chamber can reduce the exposure range of columnar joints, reduce the risk of the impact of columnar joints, and improve the conditions of the dome.