Question

The width of the horizontal floors of type A and D weirs from the foot of the drop wall to the d/s edge of the floor should never be less than ________________

(a) 5 (D + H)

(b) 3 (D + H)

(c) 2.5 (D + H)

(d) 2 (D + H)

This question was posed to me in semester exam.

Origin of the question is Tank or Surplus Escape Weirs Design topic in division River Navigation & Tank Irrigation of Irrigation Engineering

Answer 1

The correct choice is (d) 2 (D + H)

The best I can explain: The width of the horizontal floor of Type-A and Type-D weirs should not be less than 2(D + H) and in important works, the width can be increased to 3(D + H). where D is the height of drop wall and H is the maximum head of water over the wall. The rough stone apron forming a talus below the last curtain wall generally vary from 2.5(D+ H) to 5(D + H) depending upon the nature of the soil and the velocity and annual probable quantity and intensity of run-off.