DWR_2801666

• Title: WESTERN DAM ENGINEERING NEWSLETTER, VOLUME 1, ISSUE 2, JULY 2013
• Author/Source: URS
• Keywords: WAVE RUNUP, DESIGN OF RIPRAP, SLOPE PROTECTION, WAVE ACTION, DESIGN, OUTLET WORKS AIR VENTS
• Document Type - Reference Library: Research, Thesis, Technical Publications
• Document Date: 7/31/2013
• Year: 2013
• Team/Office: Dam Safety

11
Example #2:
Design embankment riprap protection for the dam
described as Example #1 in the previous article of this
newsletter. The upstream dam embankment slope is
3H:1V, the significant wave height (HS) was calculated
as 3.2 ft and the specific gravity ( ) of the riprap
source is 2.65.
Calculations:
1. Determine the required rock weight for
the riprap using Equation 1:

( )

2. Using the rock weight determine the
rock size for the riprap using Equation 2:
√

The riprap layer thickness and maximum rock
size is calculated as two times the D50 rock size.
Using the D50 rock size of 1.15 feet, DMAX is 2.3
feet.

3. Using the rock size estimate the gradation
limits using Figure 10 (TR-69). Gradation limits
for a riprap with a rock size of 1.15 feet
are shown in Table 2.
Table 2: Gradation limits for a D50 rock size of 1.15
feet.
Rock Passing Sieve Size
100% 21 to 28”
85% 19 to 26”
50% 14 to 20”
15% 2 to 9”

4. Using the guidance on the bedding layer
thickness provided in Chapter 7 of
“Embankment Dams” (Reclamation 1992),
adopt the bedding layer thickness as 12”.
Determine the gradation of the bedding and
any requirements for a filter layer in
accordance with the aforementioned
reference, TR-69 and “Design of Riprap
Revetment” (FHWA 1989).

5. Determine the limit and layout of the riprap
protection. Consider the limits described in
this article and in TR-69.