Firstly we need to know what exactly is your problem? Is your problem relevant to a dam subjected to seismic activity? If so, I think Plaxis would be your better choice, which allows users to conduct a simple simulation of earth dam subjected to seismic hazard using a built-in function that imposes base motion resulting from the record of this seismic hazard onto your earth dam. Also, Plaxis provides very user-friendly interface so that data input and output would not be difficult for you to learn.
In my opinion, FLAC could be the best software analysis for your research. FLAC, Fast Lagrangian Analysis of Continua, is numerical modeling software for advanced geotechnical analysis of soil, rock, groundwater, and ground support in two dimensions. FLAC is used for analysis, testing, and design by geotechnical, civil, and mining engineers.
The reason why this software can conduct your study is that, it has been work based on Finite Differences Method and consequensly have quick analysis with the shorter run time. Secondly it would be best software for saturated soil like earth dams. Finally it has numerous constitutive models for all the type of soils in earth and embankment dams.
Some of my research in this topic including earth dam numerical analysis would be available in my profile. It help you to be familiar with FLAC software.