ETL 1110-2-343
31 May 93
9. Special Structural Design Requirements
Concrete Report should be included. The purpose
for RCC Gravity Dams
of the Structural Report is to evaluate the ability of
the completed RCC structure to perform as assumed
a. General. The principles of design specified
during the design process. Items of particular
in EM 1110-2-2200, "Gravity Dam Design," apply
interest are:
to roller-compacted concrete gravity dams.
However, there are differences in the requirements
(1) A final stability analysis using the shear
for uplift within the body of the dam, and additional
strength values determined from the drilling and
testing requirements to assure adequate factors of
testing program.
safety against sliding.
(2) A final stress analysis using actual tem-
b. Uplift within the body of an RCC dam.
perature gradients and RCC strengths obtained from
Uplift within the body of an RCC dam constructed
instrumentation built into the structure and the drill-
without mortar bedding on all lift joint surfaces
ing and testing program.
shall be assumed to vary from 100 percent of head-
water at the upstream face to 100 percent of
(3) The percentage of the lift surfaces esti-
tailwater (or zero, as the case may be) at the down-
mated to be bonded, as indicated by the drilling
stream face. When mortar bedding is used, uplift
program.
within the body of the dam can be assumed in
accordance with the requirements for conventional
(4) A comparison of the strength indicated
concrete gravity dams.
from the post-construction drilling and testing pro-
gram with that indicated by testing performed on
c. Minimum sliding factors of safety for RCC
RCC cylinders taken during construction.
gravity dams. The minimum factors of safety
required for sliding stability of RCC gravity dams
This comparison, as well as an evaluation of the
will be as required in EM 1110-2-2200 for conven-
other testing performed during construction, should
tional concrete gravity dams. However, because of
be used to confirm that the required RCC strengths
the uncertainties and variability of cohesive strength
were obtained in the field.
at RCC lift joint surfaces, the selection of cohesive
10. The Design Team
strengths used in sliding analyses must be made
carefully. Preliminary cohesion strengths can be
a. Once the structural designer determines the
assumed in accordance with Section 8.d herein,
however, assumed values must be verified by tests
strength and serviceability requirements for a pro-
performed on samples prepared during mix design
posed RCC structure, he should work with the
in the lab and on cores taken from test fills. In
materials engineer to develop mixture designs that
addition, the Post Construction Structural Report
will achieve the desired strength and serviceability
required in Section 9.d must demonstrate that the
properties. The materials engineer should indicate
shear resistance of a typical lift joint meets or
if the desired properties are achievable with the type
exceeds the design requirements. The shear resis-
of construction to be used, and the quality of aggre-
tance of a typical joint will be the sum of the fric-
gates available. Compressive, shear, bond, and
tional resistance plus the average cohesion strength
tensile strengths in RCC construction may be as
of the bonded portion of the joint. Only the
much dependent on field control of mixing and
percentage of the joint which is bonded, as indi-
placing operations as mixture ingredients or mixture
cated by the coring and testing of the completed
proportions. Therefore, the structural and materials
structure, should be used in the calculation of
engineers must jointly develop requirements for test
cohesion strength.
fill placements, in situ testing, and actual construc-
tion placements. The in situ testing program should
d. Post construction structural report. The
address: (1) The type and numbers of tests required
drilling and testing required by Section 7.h and the
to assure that the required properties are uniformly
final structural stability and stress analysis, using
attained throughout the placement, (2) the sampling
the values obtained during the drilling, should be
procedures required to provide representative sam-
included in a Post-Construction Structural Report.
ples, and (3) the type of tests and sampling
In addition, a summary of the findings of the final
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