Modified Schaffernak's Solution for Seepage Through Earth Dam

摘要

Seepage analysis forms an important and basic part of geotechnical engineering owing to its importance in ground water contamination control, slope stability analysis and dam design. Furthermore, It is important for determining the distribution of seepage uplift pressures and the resulting seepage forces as well as the estimation of the volume of seepage losses through the body and the foundation of earth dams. Casagrande (1940) and Schaffernak (1916) improved on Dupuit's solution of seepage through earth dam without considering tail water. In this work, modification of Schaffernak's model was done to accommodate tail water. Values obtained using the new model though similar to that of the three other models (Dupuit, Casagrande and Schaffernak) shows that existence of tail water affects the value of seepage. The new model is very consistent from 3-6 m height. Though the seepage equation from the new model is similar to that of Casagrande, they differ because the value of seepage face for the tail water 'a', used for computations are not the same. For each of the model, there is a linear relationship between the seepage and the height of water upsream. Interestingly, there is a sharp change in seepage at 6m height of dam with increase in slope between 6 m and 9 m for each model except at the slope of 1:2.5 where a decrease in slope was recorded for the new model.