Study on the shear deformation of intralayer shear bands at the Baihetan hydropower station dam foundation

The engineering geological environments of the Baihetan hydropower station dam site are complicated due to the existence of columnar jointed basalt with faults and intralayer shear band structures. In the excavation process of the left dam foundation, relaxation and deformation of the columnar jointed basalt and the unloading shear deformation of the intralayer shear bands are both important engineering geological problems. Taking a typical intralayer shear band exposed during the excavation of the left dam foundation of the Baihetan hydropower station as an example, the unloading shear deformation of the intralayer shear band was investigated by in situ testing and numerical analysis in this study. The results confirmed that the unloading shear deformation of the intralayer shear bands can present an instability risk for the left dam foundation due to their poor mechanical strength and shearing damage. Therefore, a reinforcement measure of intralayer shear bands is critical for the stability assessment of similar structures.