Assessment of performance of drainage systems in earth-fill dams

Yılmaz, Ahsen Nur
Earth-fill dams are exposed to seepage throughout their lifetime. In many cases, seepage related safety precautions needed are to be taken to keep seepage rate and pore water pressures below certain limits. This is commonly handled by installation of drainage facilities which are blanket, chimney and toe drains. This study is aimed at finding suitability and the effectiveness of drainage facilities in earth-fill dams. For this purpose, various materials and geometries are considered for different drain types in separate cases. Steady-state seepage analyses are conducted using a finite element software. Results showed that increased length of blanket drain causes increased seepage flow and shorter path of phreatic line, whereas the effect of thickness of blanket drain can be neglected. The results also showed that coarser material gradation of chimney drain causes steeper phreatic line through the core. Increased height of the toe drain results in higher seepage rates through the dam. Material gradation of toe drain has not a distinct role on its performance.