Environmental Engineering Reference
In-Depth Information
Table 16.1.
Commonly accepted values for position of resultant force and compressive strength factor
(adapted from CDSA, 1999 and BC Hydro, 1995).
Load Case
Unusual post-
earthquake
Usual
and blocked drains
Earthquake (MDE)
Flood (IDF)
Inside Middle
1
/
3
rd
Outside middle
1
/
3
rd
Position of
resultant force
if other acceptance
criteria satisfied
Compressive
strength factor
(a) concrete
1.1
(2)
3
1.5
2.0
(b) foundation
(1)
4
2.0
1.3
2.7
Notes:
(1)
To be considered primarily for massive but low strength rock and weak deteriorated concrete.
(2)
Preferably 1.3.
Table 16.2.
Commonly accepted values for strength and sliding factors for gravity dams (adapted from
CDSA, 1999 and BC Hydro, 1995).
Load Case
Unusual (Post-
earthquake or
Earthquake (MDE)
[b]
Type of analysis
Usual
drains blocked)
Flood (IDF)
Peak sliding factor in
3.0
2.0
1.3
2.0
concrete (PSF) - no tests
Peak slide factor in
2.0
1.5
1.1
1.5
concrete (PSF) - with tests
[c]
Residual sliding factor in
1.1
[g]
1.5
1.0
1.3
concrete (RSF)
[d][e]
Peak sliding factor
1.5 to 2.0
1.2 to 1.4
1.1 to 1.3
1.3 to 1.5
in foundation
[f]
Notes: [a] PSF is based on the peak shear strength of the concrete or rock foundation. RSF is based on
the residual or post-peak strength. See
Section 16.3
and
16.4
for details.
[b] The stated value under the MDE load case is based on pseudostatic analysis. Performance
evaluation of the dam should also take into consideration the time dependent nature of
earthquake excitations and the dynamic response of the dam.
[c] Adequate test data must be available through rigorous investigation carried out by qualified
professionals.
[d] If PSF values do not meet those listed above, the dam stability may be considered acceptable
provided the RSF values exceed the minima.
[e] The minimum values of RSF may be reduced for low consequence dams provided data is
available to support such reduction (but not below 1.0).
[f] Assumes foundation geology and strength is assessed by a qualified geotechnical professional.
Lower values of the range apply where the geology and the strength parameters are
reasonably well known.
[g] Preferably 1.3.
Lower values of the range apply where the geology and the strength parameters are rea-
sonably well known.
It should noted that adequate sliding resistance is normally indicated by sliding factors
which equal or exceed the minimum values listed in Table 16.2. For dams in relatively
