Different types of energy dissipators may be used along with a spillway, alone or in combination of more than one, depending upon the energy to be dissipated and erosion control required downstream of a dam. Broadly, the energy dissipators are classified under two categories – Stilling basins or Bucket Type. Each of these are further sub-categorized as given below.

Stilling basin type energy dissipator:

They may fundamentally be divided into two types.

a) Hydraulic jump type stilling basins

1. Horizontal apron type (Figure 105)

2. Sloping apron type (Figure 106)

b) Jet diffusion type stilling basins

FIGURE 107: JET DIFFUSION STILLING BASIN

Bucket Type Energy-dissipator

This type of energy dissipators includes the following:

1. Solid roller bucket

2. Slotted roller bucket

3. Ski jump (Flip/Trajectory) bucket

Usually the hydraulic jump type stilling basins and the three types of bucket-type energy dissipators are commonly used in conjunction with spillways of major projects. The detailed designs of these are dealt in subsequent sections.

Since energy dissipators are an integral part of a dam’s spillway section, they have to be viewed in conjuction with the latter. Two typical examples have been shown in Figures 108 and 109, though it must be remembered that any type of energy dissipator may go with any type of spillway, depending on the specific site conditions.

PROBLEMS:

1. Explain causes of failure of earth dam

2. What are energy dissipator

3. Explain different types of spillways.

4. Explain Ogee spillway.