2019 Volume 75 Issue 4 Pages 398-414
The stability assessment of river levee against intense rainfall and flooding involves predicting variations of the phreatic surface level and pore water pressure through unsaturated seepage analysis. This study is a summary of collective work conducted by JSCE River Levee Research Committee WG2, which was set up in 2012 to investigate the applicability of unsaturated seepage analysis to the levee wetting problems in practice, and to assess the accuracy and robustness of the analysis implemented with different numerical codes by different users. To this end, three levels of round-robin analysis exercise were conducted, in which different degrees of prescription were imposed to analysis conditions. Amongst the main findings from this exercise is that all the numerical codes, whether commercial or home-grown by the authors, output sufficiently accurate and practically identical solutions when same conditions are input, despite the differences in their discretisation methods, integration methods, etc. When the participants were given a total freedom in modelling the given levee’s cross-section and material data, notable variations in the numerical results came out, confirming that each participant’s engineering judgment in conditioning/modelling, not the sensitivity of numerical codes, is the main cause of the diverse outputs. Nevertheless, the variations are on the whole within a range which can be deemed acceptable for most levee engineering purposes.