Construction of large fill dams has been increasing since 1950. The hazard of dam accident also has gotten much larger. Therefore, the development of safety evaluation system for fill dams is impending. There has been two independent approaches for safety evaluation; one is to use measured data and the other is to use numerical analysis results. However, so far, the latter has used just for formal presentation because, largely, it has used original design-values without considering any changes by damage process.
This study presents a systematic approach for damage estimation and safety evaluation using numerical methods specially focusing on seepage analysis combined with back analysis technique. First, likelihood of piping is investigated using hydraulic gradient distribution. Furthermore, when the internal damage such as piping and the change of properties such as permeability occur, the changes at several critical points inside dam core are also evaluated. Secondly, based on the former work, the validity of measured data is confirmed and schematic damage zones are estimated. Subsequently, for the precise investigation, a back analysis technique using measured pore water pressures is adopted. By applying this method to real data, the current permeability distribution and damaged zone within the core can be acquired. Furthermore, good agreement between measured data and numerical analysis result using the changed values obtained by back analysis demonstrates the validity of these approaches and hence this damage evaluation technique is very feasible and applicable. Finally, based on these results, a schematic system for safety evaluation is suggested.
