Author(s): Yoko Machida; Yasuo Nihei; Yuki Kurakami
Linked Author(s):
Keywords: River levee; Infiltration; Model test; 3D numerical analysis; Drain
Abstract: A river levee is a long linear infrastructure, and it is necessary to evaluate the stability of the whole reach of a linear river levee. However, the stability of a river levee against permeability and piping is mostly evaluated at each cross section. This study aims to evaluate the resistance of a linear river levee against permeability and to clarify the fundamental process of longitudinal variations in the permeability of a river levee. For this, we conducted 3D model tests of permeability with a model levee that was 10 m long and 0.2 m high in a large open channel. In this experiment, a constant water level in the front slope of the levee was set. We also conducted a 3D unsteady permeability simulation using a commercial software. The results of the laboratory experiments indicated that variations in the hydraulic conductivity in the longitudinal direction appeared, even though the model levee was set uniformly in the longitudinal direction. It was also found that slope collapses occurred in longitudinal locations with high hydraulic conductivity and at the construction boundary of the levee. Further, it was found that the drain of the back slope of the levee can prevent slope collapse significantly in the longitudinal locations with and without drains in the section. The simulated results show that a mixing layer of permeability appeared near the boundary between relatively high and low hydraulic conductivities, and the thickness of the mixing layer increased with the difference in hydraulic conductivity.
Year: 2018