2024 Volume 65 Issue 3 Pages 100-111
A low-dip angle weak layer (FL-D) emerged in the riverbed as the excavation progressed for the main dam foundation of the Nam Ngiep 1 Hydropower Project. A series of geological investigation, testing such as mechanical and physical tests, and studies of literatures were carried out in order to understand mechanical and physical properties of FL-D. Since it is thought that the strength of the weak part varies depending on the segments due to their origins, we adopted the plasticity index method and the direct shear test to obtain representing strength of the entire weak layer, which are the adhesion of c=0 and the internal friction angle of φ=25°. As a result of the stability analyses, we adapted the shear key structure in addition to excavation of FL-D in a certain area to ensure the stability of the dam against sliding.
