Geoscience Reference
In-Depth Information
•
A guide only. Depends on risk level.
•
Use of dynamic analysis where F.S.
<
1.1. Deformations then govern.
14.12 Typical slopes for low height dam walls
•
The size of dams discussed herein as
<
5m (low); 5 to 15m medium;
>
15m High.
•
In a risk-based design, size is judged on volume of water retained, and its effect
on the people and environment. Typically a dam with height less than 5m is a low
risk to the community, although it can affect those locally on the property.
Table 14.12
Typical slopes of low height, homogeneous dam walls (USDI, 1965).
Subject to drawdown
Soil classification
Upstream slope
Downstream slope
No
GW, GP, SW, SP
N/A (Pervious)
N/A (Pervious)
Usual farm design storage
GC, GM, SC, SM
1V: 2.5H
1V: 2.0H
Designs
CL, CH
1V: 3.0H
1V: 2.5H
CH, MH
1V: 3.5H
1V: 2.5H
Yes
GW, GP, SW, SP
N/A (Pervious)
N/A (Pervious)
Drawdown rates
>
150 mm/
GC, GM, SC, SM
1V: 3.0H
1V: 2.0H
day
CL, CH
1V: 3.5H
1V: 2.5H
CH, MH
1V: 4.0H
1V: 2.5H
•
Other dam considerations on seepage below and through dam walls, as well as
overtopping needs to be considered.
•
Drawdown rates as low as 100mm/day can be considered rapid in some cases.
14.13 Effect of height on slopes for low height dam walls
•
In the design of dam walls, zoned embankments provide the advantage of steeper
slopes, and to control drawdown/ seepage effects.
•
Zoned embankments are recommended for dam heights exceeding 6m.
•
Slope stability analysis required for zoned walls. The slope guidance shown is for
homogeneous earth dams.
Table 14.13
Typical slopes of homogeneous dam walls (Nelson, 1985).
Slope
Height of wall
(m)
Location
GC
SC
CL
CH
1V: 2.5 H
1V: 3.0 H
Upstream
3
1V: 2.0 H
1V: 2.5 H
Downstream
1V: 2.5 H
1V: 3.0 H
Upstream
3 to 6
1V: 2.5 H
1V: 3.0 H
Downstream
Upstream
1V: 3.0 H
1V: 3.5 H
6 to 10
Downstream
1V: 2.5 H
1V: 3.0 H
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