Introduction - Geotechnical Engineering of Dams - page 2

Table 1.1. Embankment dam zones description and function.

Zone Description Function

1 Earthfill (“core”) Controls seepage through the dam

2A Fine filter (or filter drain) (a) Controls erosion of Zone 1 by seepage water, (b) Controls

erosion of the dam foundation (where used as horizontal drain),
(c) Controls buildup of pore pressure in downstream face when
used as vertical drain

2B Coarse filter (or filter drain) (a) Controls erosion of Zone 2A into rockfill, (b) Discharge

seepage water collected in vertical or horizontal drain

2C (i) Upstream filter Controls erosion of Zone 1 into rockfill upstream of dam core

(ii) Filter under rip rap Controls erosion of Zone 1 through rip rap

2D Fine cushion layer Provides uniform support for concrete face; limit leakage in the

event of the concrete face cracking or joints opening

2E Coarse cushion layer Provides uniform layer support for concrete face. Prevents

erosion of Zone 2D into rockfill in the event of leakage in
the face

1-3 Earth-rockfill Provides stability and has some ability to control erosion

3A Rockfill Provides stability, commonly free draining to allow discharge

of seepage through and under the dam. Prevents erosion of
Zone 2B into coarse rockfill

3B Coarse rockfill Provides stability, commonly free draining to allow discharge

of seepage through and under the dam

4 Rip rap Controls erosion of the upstream face by wave action, and

may be used to control erosion of the downstream toe from
backwater flows from spillways

4

water level

1

natural surface

2C

cut-off
foundation

general
foundation

HOMOGENEOUS EARTHFILL - SCALE A

4

1

2B

2C

2A

4

EARTHFILL WITH TOE DRAIN - SCALE A

4

2C

1

1-3

ZONED EARTHFILL - SCALE B

Figure 1.1. Schematic cross sections of typical earthfill dams.