Environmental Engineering Reference
In-Depth Information
Zone 4/5 Boundary Not Defined
3/4,11
3,-
4
8
1/2,-
1,-
3/2,-
4/5,-
5,L
1,-
2/3,-
5,-,L
3/4,-,L
4,3,L
4,-
2/1,15
4,10
3
1,-
1,-
1,-
5,-
5,-
1
,-
0,
-
2
1,-
1,-
2,0
3,-
4,0
2,-
7
0,0
1
1/2,0
1/2,0,sL
1,0,sL
2,0
1,9
0/1,9
1/0,-
2,-
1,0
1,80
0
6
Data Set 1
Data Set 2
Data Set 3
Data Set 4
Data Set 6
Data Set 7
Data Set 8
D
ata Set 9
Damage Contours
0,-
1
,-
0,1
LEGEND
1/2, 14, L
5
Liquefaction
14meters of alluvium
Class 1/2 Damage
4
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
(B)
Figure 12.35.
Earth and Rockfill Dams - contours of damage class versus earthquake magnitude and
peak ground acceleration. (A) Earthquake magnitude. (B) Foundation peak ground accel-
eration (as a fraction of acceleration due to gravity). Contours drawn without considera-
tion for cases that had liquefaction. Boundaries shown assume rockfill is well compacted.
For dumped or poorly compacted rockfill use
Figure 12.34
to estimate the damage (Pells
and Fell, 2003).
- Dams which experience damage of Class 2 (relative settlement of 0.2% to 0.5% and/or
longitudinal cracks 30-80 mm wide) or greater are highly likely to experience trans-
verse cracking. However, transverse cracking has been observed at under M6.0 to M6.5
earthquakes, at PGA as low as 0.1 to 0.15 g.
- There is evidence to show that higher seismic loads will result in the formation of larger
and deeper cracks, and are more likely to cause transverse cracking due to the greater
differential settlements across the valley.
- At low seismic loading, there is evidence to show that only one type of cracking is likely
to develop. This may be either longitudinal (more common) or transverse, depending
on factors within the embankment that make it predisposed to a particular form. It is
the nature of the embankment, zoning and the foundation geometry and presence of
compressible materials and not the seismic loading, that differentiate between which
form of cracking develops, and in particular determine whether transverse cracking
occurs at low seismic intensities.
- The susceptibility of an embankment to a particular type of crack could not be related
to dam type, but a weak relationship has been developed with dam shape - dams in
steeper valleys tend to be more susceptible to transverse cracking near the abutments.
Fong and Bennett (1995) give some limited information on maximum transverse crack
depth as a function of crest settlement and crest length. This shows:
Maximum crack depth
(m)c (settlement/dam crest length)
where “c” is usually about 1000 to 2500, but ranges from 125 to about 10,000.
