Environmental Engineering Reference
In-Depth Information
Table 15.17.
Factors to be considered and methods for assisting in the estimation of the likelihood of
formation of a breach in CFRD.
Methods for assisting in the estimation
Breach and mode Factors to consider
of likelihood of formation of a breach
Slope instability
• Estimated likely flow
Initiator mechanism, continuation and
and unravelling
rate of the leak
progression factors, ability to intervene
to seal leak; historic precedents for modern
and older CFRD (section 18.6.)
• Ability to intervene, draw
Account for location and capacity of
down the reservoir
outlet works, reservoir volume, river
inflows; accessibility of site, availability of
barges, personnel, whether the joint or
opening is covered by debris, zone 1A etc.
•Presence of alluvium
Consider in relation to the breach
in the foundations
mechanism
• Reservoir level at the time of the
Assess from hydrology
concentrated leak, freeboard above
that level, and the ability
Unravelling
• Discharge capacity of rockfill
Estimate from zoning, particle size
zones, compared to estimated
distribution, presence of still meshing on
leakage flow rates, giving
downstream fall and methods for
gradients through the dam
assessing critical gradients using
Pinto (1999), Marulandan and Pinto
(2000), Solvick (1991), Olivier (1967)
Slope instability
• Discharge capacity of rockfill zones
As above. Calculate factors of safety,
compared to estimated leakage flow
property allowing for non-linear strengths
rates, giving pore pressure rise
of the rockfill materials, and high friction
in the dam
angles at low confining stress.
•Effect of downstream slope
Assess as a filter against the
protection/steel meshing, which may
eroding fines for no-erosion, excessive
act as a filter to eroding material,
erosion and continuing erosion criteria
causing pore pressures to rise.
(Foster and Fell, 2001)
FURTHER READING
This chapter has set out to summarize the history of development, features, and perform-
ance of CFRD. Those seeking more detail should refer to the following volumes:
J. Barry Cooke Volume, Concrete Face Rockfill dams. Chinese Committee on Large Dams, Beijing,
September 2000.
Proceedings, International Symposium on Concrete Face Rockfill Dams, September 2000,
International Commission on Large Dams, Paris.
Proceedings, Second Symposium on Concrete Face Rockfill Dams, Comite Brasileiro de Barragens,
Rio de Janeiro, October 1999.
