EP 1110-2-13
28 Jun 96
Appendix D
(3) Problems of placement and compaction
complicated because of restricted access.
Construction
(4)
Initial fill placement on rock foundation.
D-1. General
b. Failure to detect and remove localized areas
of soft foundation material.
Construction is a critical phase in achieving a safe dam
because operational problems often go back to mistakes
(1)
Potential differential settlement and cracking.
made in design and construction (James 1990). Projects
must be continuously evaluated and "re-engineered," as
(2) Important factor in stability of dam and
required, during construction, to ensure that the final
foundation.
design is compatible with conditions encountered
during construction (Federal Emergency Management
c.
Preparation and treatment of cutoffs in
Agency 1979). Construction considerations of earth
foundations and abutments - one of the most important
and rock fill dams are discussed in EM 1110-2-2300
factors in embankment dam construction.
and EM 1110-2-1911.
(1) Failure to achieve an adequate cutoff to
sound rock or an impervious strata.
D-2. Construction/Design Interface
(2) Failure to achieve adequate reduction in
Dam safety is an integral part of the planning, design,
seepage volume or pressure with grout curtain or to seal
construction,
and
operation
of
a
dam.
off large channels or voids.
Construction/design interface is essential. This is
accomplished through the report on engineering
(3) Failure to achieve adequate surface treatment
considerations and instructions to field personnel,
of joints, potholes, treatment of overhangs, loose rock
preconstruction orientation for the construction
on abutments, or inadequate bond between
engineers by the designers, and required visits to the
embankment and foundation.
site by the designers.
d. Construction problems during installation of
drains and filters.
D-3. Problems to Watch for During
Construction
(1) Piping can result from failure to achieve
filter criteria due to segregation of material which may
Specific problems with safety implications to watch for
occur in transition to rockfill or in exit details.
during construction include (James 1990):
(2) Inadequate drainage capacity because of
a.
Contacts between fill and rock or concrete.
improper gradation, dirty (excessive amount of fines)
materials, material breakdown during placement, or
(1) Problems due to dissimilar compressibility
contamination of the filter with impervious material
leading to differential settlement and voids or cracks
from the adjacent core due to traffic or due to surface
within the embankment.
erosion caused by rainfall.
(2) Critical areas at rock abutments (particularly
e.
Failure to detect critical zones such as voids
for steep slopes or slope breaks), spillway contacts,
or strata, or lenses, of pervious materials in foundations
adjacent to conduits, and at contacts with existing fill
without cutoffs.
which have had time to undergo settlement.
(1)
Inadequate or no pressure relief.
D-1
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