Question

What is the formula for the upstream apron length according to Bligh?

(a) 2.208 (CH)^1/2

(b) 2.208 (H/13)^1/2

(c) 2.208 (H)^1/2

(d) 2.208 (C/H)^1/2

This question was posed to me in semester exam.

This interesting question is from Seepage Theories in portion Seepage Theories and Weirs and Barrages Design of Irrigation Engineering

Answer 1

Correct answer is (a) 2.208 (CH)^1/2

Explanation: The upstream apron length according to Bligh is 2.208 (CH)^1/2, where C is the creep coefficient and H is the head of water against the weir. The downstream apron length is given by 2.208 (H/13)^1/2 which should be sufficient to withstand uplift pressures below it.