Question

Projecting collars are provided on sides of a rectangular tunnel of length L made through an earthen dam to increase the seepage path. Their projection length (X) and numbers (N) are decided so as to provide increased seepage path equal to 2NX where 2NX should generally be ______________________

(a) greater than L/4

(b) greater than L/3

(c) greater than L/2

(d) greater than L

I have been asked this question in exam.

This interesting question is from Dam Outlet in section Pressure Conduits, Outlet Works through Dams and Rivers of Irrigation Engineering

Answer 1

Correct answer is (a) greater than L/4

To explain: The seepage is reduced by increasing the length of the seepage path by at least 25%. The increase in seepage path must generally be greater than L/4.