Geotechnical News • March 2015
49
GEOSYNTHETICS
long and obviously expensive dams”
(Fahlbusch, 2009).
The International Commission on
Large Dams (ICOLD), using the most
recent publication of the World Regis-
ter of Dams, recognises that for single-
purpose dams “48% are for irrigation,
17% for hydropower, 13% for water
supply, 10% for flood control, 5% for
recreation, and less than 1% for navi-
gation and fish farming”. A growing
appreciation for dam safety and dam
risk management, has contributed to
advances in technology across a wide
range of subject areas, including the
role of seepage-control in civil, mining
and environmental structures. ICOLD,
founded in 1928, provides guidance
to dam engineering practitioners in
pertinent aspects of these advances.
The use of geotextiles as filters and
transitions in dams was first addressed
its Bulletin 55 of 1986. It provided
guidance to the designer on applica-
tions and limitations for consider-
ation as understood at that time. The
approach was conservative, in keeping
with conventional dam engineering
philosophy and, it could be argued,
reasonably so given the somewhat
limited knowledge of polymers and
geotextile performance within the
profession. Although a number of
dam engineers had incorporated the
use of geotextiles, most notably the
Valcross Dam in France, the long-term
performance in these applications was
neither widely-disseminated nor fully
understood at that time. Thus the use
of geotextiles as filters and transitions
was largely limited to applications
that offer easy access for repair in the
event of unsatisfactory performance,
such as under upstream riprap and
beneath downstream toe drains.
Timblin (1988) reports on 7 categories
for the location of a geotextile filter
in an embankment dam (Table 1),
making reference to the purpose of
the filter, the type of flow, the sig-
nificance of failure, and the ease of
access for repair. Following a short
yet succinct review of geosynthetics
in dam construction, he ventured that
“with proper selection of materials,
good design procedures, and a strong
testing program, geosynthetics offer a
valuable set of new materials for the
advanced dam engineer”.
Current regulatory guidance in
North America
The United Sates Society on Dams
(USSD, 2011) considered the use of
geosynthetics as a construction mate-
rial for embankment dams, including
specific reference to geotextiles as fil-
ters in fill dams. Also in that year, the
US Federal Emergency Management
Agency (FEMA, 2011) published on
the subject of filters for embankment
dams, with the objective of report-
ing on best practices for design and
construction, and with commentary on
the use of geotextile in filter/drainage
systems for dams (Fig. 1). In a third
contribution of that same year, the US
Bureau of Reclamation (USBR, 2011)
issued a ninth revision to Design
Figure 1. The beginning of the Bronze Age witnessed the oldest known
embankment dams.
