Environmental Engineering Reference
In-Depth Information
Unknown
No warning signs observed
Failures
Accidents
Increase in pore pressures
Whirlpool in reservoir
51 failure cases
102 accident cases
Cracking
Settlements
Sinkholes
Muddy leakage
Increase in leakage
05 015
20
25
30
35
40
45
50
No. of cases
Figure 20.3.
Observations during piping incidents - piping through the embankment (Foster et al., 1998).
Unknown
Failures
Accidents
No warning signs observed
Excess pore pressures
21 failure cases
85 accident cases
Whirlpool in reservoir
Sandboils
Cracking
Settlements
Sinkholes
Muddy leakage
Increase in leakage
0
5
10
15
20
25
30
35
40
No. of cases
Figure 20.4.
Observations during piping incidents - piping through the foundation (Foster et al., 1998).
- Cracks and piping associated with broad changes in the abutment profile are generally
“located at depths of less than one third of the height of the dam”;
- Piping associated with small scale irregularities in the foundation generally occurs close
to the foundation surface and usually in the lower half of the core.
Foster et al. (1998, 2000a) record that in 80% of failures by piping through the
embankment the reservoir was at or higher than the previous highest reservoir level. For
the other recorded cases it was within 1 metre of the previous highest level.
For piping in the foundation the reservoir water level was often at or above the historic
high, but there were some failures with somewhat lower reservoir levels.
Figures 20.3 and 20.4 show observations during piping incidents in the embankment
and foundation.
