Rockfill dam, a kind of embankment or so called earth-rock dams, is a water retaining barrier composed of three major parts: fill of loose rock by dumping or roller compaction; impervious membrane made of masonry, concrete, asphaltic concrete, steel sheet piles, timber, or other materials; and transition layer. The impervious membrane is employed as the waterproof and can be placed either within the embankment or on the upstream slope. Although the history is short compared to that of other ancient dam types, the development of rockfill dams during the last several decades was booming around the world (Chen et al.