embankment dams is illustrated in Fig. 1.1. Secondary embankment dams
and a small minority of larger embankments may employ a homogeneous
section, but in the majority of instances embankments employ an impervi-
ous zone or core combined with supporting shoulders which may be of
relatively pervious material. The purpose of the latter is entirely structural,
providing stability to the impervious element and to the section as a
whole.
Embankment dams can be of many types, depending upon how they
utilize the available materials. The initial classification into earthfill or
rockfill embankments provides a convenient basis for considering the prin-
cipal variants employed.
- Earthfill embankments.An embankment may be categorized as an
earthfill dam if compacted soils account for over 50% of the placed
volume of material. An earthfill dam is constructed primarily of
selected engineering soils compacted uniformly and intensively in
relatively thin layers and at a controlled moisture content. Outline
sections of some common variants of the earthfill embankment are
illustrated in Fig. 1.2. - Rockfill embankments. In the rockfill embankment the section
includes a discrete impervious element of compacted earthfill or a
slender concrete or bituminous membrane. The designation ‘rockfill
embankment’ is appropriate where over 50% of the fill material
may be classified as rockfill, i.e. coarse-grained frictional material.
EMBANKMENT DAM TYPES AND CHARACTERISTICS 13
Fig. 1.1 Earthfills and rockfills in dam construction