Environmental Engineering Reference
In-Depth Information
research into embankment performance and fail-
ure modes, current UK visual inspection guidance
and visual inspection methods used elsewhere.
The 10 performance features identified are:
1
animal burrowing/vermin infestation;
2
foreign objects in the crest or rear slope concen-
trating the erosion process;
3
cracking and/or fissuring;
4
third-party damage (cattle, vehicles, etc.);
5
direct evidence of seepage or piping;
6
visible deformation of cross-section caused by
piping;
7
visible deformation of cross-section caused by
slope instability;
8
revetment condition;
9
erosion of cross-section;
10
vegetation condition (outer slope).
Fig. 6.4
Overtopping leading to breach failuremode (HR
Wallingford 2004).
erosion of the outer slope will eventually lead to a
breach of the embankment once the rear of the
embankment has been sufficiently weakened.
Signs of this failure mode will be most evident
in terms of erosion of the rear of the crest and
the outer slope. The vegetation covering the
outer slope is likely to be damaged and eventually
lost due to the overflowing water. Grass cover acts
as protection against erosion caused by overtop-
ping, and the loss of this cover will be a key
indicator that a damaging level of overtopping is
occurring.
Contribution of performance features
to failure modes
The contributions linking performance features
to failure modes for an earth embankment are
shown in Table 6.1. These were determined
through a consensus of expert opinion combined
with previous research work into the perfor-
mance of embankments (HR Wallingford 2003),
and were devised for use in the pilot trials of the
condition indexing process.
Performance features
A set of performance features were proposed
in collaboration with industry experts based on
Table 6.1
Contributions Linking Performance Features (PFs) to Failure Modes for an Earth Embankment
Contributions
Slope
instability
Revetment
failure
Back
ll
washout
Overtopping
leading to breach
Performance features
Piping
Animal burrowing/vermin infestation
0.1
0.2
0.2
0.2
0
Foreign objects in the crest or rear slope
concentrating the erosion process
0.1
0.2
0.1
0.2
0.2
Cracking and/or
ssuring
0.3
0.1
0.2
Third party damage (cattle, vehicles etc)
0
0.1
0
0
0.2
Direct evidence of seepage or piping
0
0
0.5
0.2
0
Visible deformation of cross-section
0.3
0
0.1
0
0
Revetment condition
0.2
0.5
0
0.2
0
Erosion of cross-section
0
0
0
0
0.4
Vegetation condition (outer slope)
0
0
0
0
0.2
