Question

What is the expected solution for the case when the T.W.C is lying above the J.H.C curve at all discharges?

(a) By providing a simple concrete apron of length 5(Y1 – Y2)

(b) By providing a sloping apron above the river bed

(c) By providing a sloping apron below the river bed

(d) Provision of a ski-jump bucket

The question was asked in unit test.

My question is based upon Energy Dissipation Below Overflow Spillway in portion Spillways, Energy Dissipators and Spillway Gates of Irrigation Engineering

Answer 1

The correct option is (b) By providing a sloping apron above the river bed

The explanation is: When the TWC is lying above the JHC at all discharges, the problem can be solved by-

1) By constructing a sloping apron above the river bed

2) By providing a roller bucket type of energy dissipator.

In this case, the jump is formed at the toe will be drowned by the tail-water and little energy will be dissipated.