SEEPAGE MODELING IN EMBANKMENT DAMS WITH VARIOUS SUB SOIL CHARACTERISTICS

The embankment dam has the advantage that it can be built in all sub-base conditions although poor topography, but weakness is seepage, so research on seepage needed. This study uses numerical modelling with GeoStudio program: SEEP/W and SLOPE/W. data used from Tugu Dam, Trenggalek, while subbase five soil types, namely clay, silty silt, sand, sand. simulation divided into two; first condition of characteristics remains water level increasing every 5 meters base elevation to below floodwater level;. In contrast, second constant, change. Each will checked for discharge stability. results show have a logarithmic correlation R 2 > 0.75. largest 1,90 x 10 -3 m 3 /s sand soil, smallest clay 1,47 -9 /s. saturated volumetric content also correlation, some cannot because they an value < From two simulations, occurs said safe average annual runoff which 1% 10-year re-flood calculated using Nakayasu Synthetic Unit Hydrograph (HSS) 5.99 /s, safety factor slope stability 1.2 then considered stable.