Environmental Engineering Reference
In-Depth Information
Table 20.8.
Rate of development and detectability of internal erosion and piping - piping through the
foundation, and from the embankment to the foundation (Fell et al., 2001, 2003).
Phase of
Usual rate of
Ease of
Method of
development
Mechanism
development
detection
detection
Initiation -
Backward erosion
Slow
Difficult
Visual, seepage,
Foundation
pore pressure
Backward erosion
Rapid to very rapid
Readily to
following “blow-out”
difficult
Backward erosion along
Slow to Rapid
Moderate to
concentrated leak
difficult
Suffusion/internal
Slow
Moderate to
instability
difficult
Initiation -
Backward erosion
Slow to rapid/very
Difficult
Pore pressure,
embankment
rapid
seepage
to foundation
Continuation
Filters satisfying no
Erosion will cease
erosion criteria
if all seepage is
intercepted
Filtered exit, satisfying
Medium to slow, but
Moderate to
Seepage, pore
excessive erosion, or
could be rapid
difficult
pressure,
incomplete seepage
visual
interception
Filtered exit, not
Rapid to slow
Difficult to
Seepage, pore
satisfying continuing
moderate
pressure,
erosion criteria, or
visual
unfiltered exit
Progression
Gross enlargement in
Assess time from
to form a
the foundation or in the
Table 20.2:
pipe, and
embankment; and slope
- Very rapid or rapid
Moderate to
Seepage,
a breach
instability linked to
- Medium or slow
readily
visual
development of a pipe.
Assess rate of erosion
Readily
Crest settlement or/and
from Table 20.4,
Readily
Visual,
sinkhole in embankment
and other factors
survey,
from Table 20.5.
seepage
Usually slow to
medium
Slope instability, and
Assess erosion rate
unravelling or sloughing
from Table 20.4,
for piping embankment
and other factors
to foundation
from Table 20.5
Usually slow to
Moderate to
Visual,
medium, unless
readily
survey,
linked to rapid
seepage
development of
a pipe
Legend: Rate of development: Slow
weeks or months, even years; Medium
days or weeks;
Rapid
hours (
12 hours); Very Rapid
3 hours. Ease of detection: Difficult
unlikely to be
detected in most cases; Moderate
readily detected in most
cases. Methods of detection: Visual (inspection), seepage (measurement either visual or by instrument),
pore pressure (measurement), survey (survey of surface markers to determine horizontal and vertical
deformations).
may be detected in some cases; Readily
