Question

During the maintenance of an earthen dam, the apparent seepage through the foundation of the dam is best taken care of by providing ______________________

(a) chimney drain

(b) rock toe

(c) drain trench along the downstream toe

(d) upstream impervious cut-off

This question was addressed to me in a national level competition.

This key question is from Rock Fill Dams topic in chapter Earthen and Rock Fill Dams of Irrigation Engineering

Answer 1

The correct answer is (c) drain trench along the downstream toe

Explanation: Cut-off can be provided only during construction. If seepage appears afterward, a drain with an inverted filter along the toe line is provided to collect soil-free water to check piping action.