Author(s): Mehmet Sukru Guney; Merve Okan; Emre Dumlu; Asli Turkben; Pelin Aklik; Gokmen Tayfur

Linked Author(s): Emre Dumlu

Keywords: Earth-fill dam; Piping; Breach geometry; Breach development; Discharge through breach; PLAXIS 3D

Abstract: Internal erosion, also known as piping, is one of the most important causes of earth-fill dam breaks. According to the U.S. Department of the Interior Bureau of Reclamation almost 30% of dam failures are due to piping. Many researchers dealing with numerical analyses in this area make some simplified assumptions about the shape of the breach and the discharge of water flowing through the breach. In the scope of the project supported by the Scientific and Technological Research Council of Turkey, an experimental system was designed and built at Izmir University of Economics. The aim of the project is to investigate the mechanism of the breach resulting from the piping in earth-fill dams. This study consists of experimental and numerical studies in order to provide data needed to perform numerical analyses with more realistic approaches. A dam with a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m was built in a flume 1 m wide, 0.81 m high and 6.14 m long. Before the construction of the dam, some common soil mechanics tests were carried out. The dam was constructed by using a mixture consisting of 85 % sand and 15 % clay. The permeability of the sand which has a mean diameter of 0.325 mm was found to be k= 4.66x10-4 cm/sec. A circular tunnel with a diameter of 2 cm was created along the centreline at 6 cm below the dam crest. In the closed system, water was pumped from the lower reservoir to the upper channel. The water level was adjusted by means of an electromagnetic sensor so that the pump starts and stops when water depth in the channel was 0.54 m and 0.56 m, respectively. The dam was constructed layer by layer. Each layer of 14 cm was compacted so that its thickness becomes 10 cm by using Proctor hammer and plate. Flow rate of water delivered by the pump was measured by magnetic flow meter. Six cameras located at different locations recorded the evolution of the dam failure. Gauss Area formula was applied to determine the time-varied of the breach areas at upstream and downstream sides. The discharge of water through the breach and average flow velocity were determined by using the continuity equation. The changes in water depth in the channel were also recorded. The experimental findings were evaluated and interpreted using the numerical results based on the three-dimensional finite element analyses, obtained from the software PLAXIS-3D.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221298

Year: 2022