Question

What is the correct calculation for balance floor length?

(a) Total length – (the downstream length + twice the cut-off length)

(b) Total length + (the downstream length + twice the cut-off length)

(c) The downstream length – twice the cut-off length

(d) The downstream length + twice the cut-off length

This question was posed to me during an online exam.

The question is from Seepage Theories in section Seepage Theories and Weirs and Barrages Design of Irrigation Engineering

Answer 1

Correct answer is (a) Total length – (the downstream length + twice the cut-off length)

The explanation is: In order to prevent the scour from reaching the pucca floor, upstream and downstream aprons are provided and the length of these aprons are put forward by Bligh’s formulas. The cut-off is provided by Khosla’s theory and then the balance floor length is provided under the crest and on the upstream side.