Question

What is the empirical formula given by Bligh for the design of the top width of the weir wall?

(a) B’ = H / (G-1)

(b) B’ = H / (G-1)^1/2

(c) B’ = (H + height of weir)/G

(d) B’ = H / (G+1)

I have been asked this question in homework.

My query is from Seepage Theories in section Seepage Theories and Weirs and Barrages Design of Irrigation Engineering

Answer 1

Correct choice is (b) B’ = H / (G-1)^1/2

Easy explanation: According to Bligh, the top width of weir wall (B’) is given by H / (G-1)^1/2 where H is head of water over the weir wall at the time of maximum flood and G is the specific gravity of floor material. The top width generally varies from 1.5 m to 1.8 m.