End Effects in Models for Seepage below Weirs

The determination of the seepage pattern beneath weirs on pervious foundations often requires model experiments. In these models the pervious reaches on the upstream and downstream sides can be reproduced only up to a finite length while in the prototype these lengths are very large. If the length reproduced is small, considerable error is introduced in the values of uplift pressures determined by model experiments. By an analytical approach, the minimum length of pervious reach to be reproduced in the model, to keep down the error to a specified maximum, is determined and presented in a graph. Though the problem is solved for a simple profile, it is expected that the results will generally hold good for other cases as well.