Environmental Engineering Reference
In-Depth Information
Figure 13.5.
Upstream slope protection.
Rip-rap comprises quarried blocks of rock which have to be:
- Large enough to dissipate the energy of the waves without being displaced;
- Strong enough to do this without abrading or without breaking down to smaller sizes;
- Durable enough to withstand the effects of long term exposure to the weather and vary-
ing periods of inundation without becoming weaker and, hence, wearing or breaking down
to smaller sizes.
For earthfill dams, the rip-rap is constructed as a separate layer and should be under-
lain by a filter to prevent erosion of the earthfill through the rip-rap as shown in Figure
13.5(a). Alternatively a wider zone of quarry run rockfill with the larger rocks pushed to
the upstream slope may be adopted. For earth and rockfill dams the rip-rap is often
obtained by pushing the larger rock from Zone 3B to the edge, although in some very
large rockfill dams large rocks have been selectively placed by an excavation with “claws”
