Experimental Study of the Evolution of the Breach and the Discharge through the Breach Resulting from Piping Due to Seepage at the Mid-part of Earthfill Dam

Abstract

—One of the main factors that leads to earth-fill dam failures is the internal erosion, commonly referred to as piping. Regarding the geometry of the breach and the discharge of water flowing through the breach, many researchers working with numerical analyses in this field make some simplified assumptions. This study was carried out as a part of the project supported by the Turkish Council for Scientific and Technological Research (TUBITAK) and it includes experimental research with the goal of supplying the data required to carry out numerical analysis using more realistic approaches. A dam with a height of 65 cm, a bottom width of 200 cm and a crest width of 5 cm 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 % fine sand and 15% clay. In order to generate the formation of the breach, a square shaped rock salt layer of 2 cm side lying from upstream to downstream was placed at 28 cm from the bottom of the dam body. The progression of the dam failure was captured by six cameras located at different locations. Gauss Area formula was applied to determine the time-varied 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 continue to be compared with numerical results obtained from the software PLAXIS 3D.