Large-scale test of a coarse sand barrier as a measure against backward erosion piping

A novel remediation technique against backward erosion piping is being investigated in a multi-scale experimental program. The coarse sand barrier (CSB) is a trench containing densified coarse sand that is placed below an embankment dam or levee in order to prevent the upstream progression of a pipe. The effectiveness of the measure is based on the larger resistance of the densified coarse sand in the barrier against piping erosion, and on the low hydraulic load in the barrier resulting from the conductivity contrast between barrier and background material. This method was investigated in laboratory experiments on a small-scale (aquifer depth 0.10 m) and a medium-scale (aquifer depth 0.40 m) and was found promising. In order to increase the confidence in the potential of the measure for application in the field, two experiments at a larger scale (aquifer depth 3 m) were conducted. This contribution presents the analysis of the piping process of the first large-scale experiment based on measurements during the test and excavation of the sample after the test.