Environmental Engineering Reference
In-Depth Information
Table 20.7.
Rate of development and detectability of internal erosion and piping - piping through the
embankment (Fell et al., 2001, 2003).
Phase of
Usual rate of
Ease of
Method
development
Mechanism
development
detection
of detection
Initiation
Backward erosion
Slow, but rapid to very
Difficult (unless
None? Visual if on
rapid at the end
observed at
the downstream
downstream
face
face)
Crack/hydraulic
Rapid or very rapid
Difficult
Seepage, visual if
fracture
the crack
emerges on the
downstream
face or if
crest, or the
crest settles
High permeability
Slow to rapid
Moderate to
Seepage, pore
zone
difficult
pressure visual if
emerges on
downstream face
High permeability or
Rapid or very rapid
Difficult
Seepage, visual
cracking, hydraulic
fracture, associated
with conduits
or walls
Suffusion/internal
Slow
Moderate to
Pore pressure,
instability
difficult
seepage, visual if
emerges on the
downstream face
Continuation
Filters satisfying
Erosion will cease
no-erosion criteria
Filters satisfying
Slow to rapid
Moderate to
Seepage, pore
excessive erosion
difficult
pressure
criteria
Filters not satisfying
Medium to rapid
Moderate to
Seepage, pore
continuing erosion
difficult
pressure
criteria, or no filters
Progression to Gross enlargement;
Assess time from
form a pipe,
and slope instability
Table 20.2
and a breach
linked to
- Very rapid or rapid
Mod. to readily
Seepage, visual
development
- Medium or slow
Readily
of a pipe
Assess rate of erosion
Readily
Visual, survey,
Crest settlement or/
from Table 20.4, and
seepage
and sinkhole in
other factors from
embankment
Table 20.5. Usually
slow to medium
Slope instability,
Assess erosion rate
Moderate to
Visual, survey,
unravelling or
from Table 20.4, and
readily
seepage
sloughing
other factors from
Table 20.5. Usually
slow to medium unless
linked to rapid
development of pipe
Legend: Rate of development: Slow
weeks or months, even years; Medium
days or weeks; Rapid
hours (
12 hours) or days; 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 instruments), pore pressure
(measurement) survey (survey of surface markers, to determine horizontal and vertical deformation).
may be detected in some cases; Readily
