- Load transfer and continuity.Although gravity dams are traditionally
designed on the basis of independent free-standing vertical can-
tilevers it is normal to provide for a degree of interaction and load
transfer between adjacent blocks. This is effected by forming inter-
locking vertical shear keys on the construction joint face (Fig. 3.19).
In the case of arch and cupola dams it is essential to provide horizon-
tal continuity to develop arch action. The construction joints of such
dams are therefore grouted after the structure has cooled to its
lowest mean temperature to ensure effective load transfer and
monolithic arch action. Joint grouting has also been carried out on a
number of gravity dams.
- Pulvino.A thick perimetral concrete ‘pulvino’, or pad, is frequently
constructed between the shell of a cupola dam and the supporting
rock (Fig. 3.15). It assists in distributing load into the abutments and
foundation. The shell may be separated from the pulvino by a
perimetral joint to avoid fixity moments and hence induced tensile
stress at the upstream face.
- Concrete zoning.A zone of richer facing concrete some 1–1.5 m thick is
frequently poured at either face. The richer concrete mix, which is
generally also air-entrained, is provided to improve durability and, on
the spillway face, resistance to cavitation damage and erosion. On the
largest gravity dams the interior or hearting concrete may also be
zoned for reasons of economy. Cement content, and therefore concrete
strength, is then reduced in stages with increasing elevation (Fig. 3.20).
3.5.5 Construction planning and execution
Efficient and economic construction requires thorough planning of each of
the principal phases, e.g. foundation preparation, concreting, etc. It is also
necessary to pre-plan for the concurrent operations contributing to each
168 CONCRETE DAM ENGINEERING
Fig. 3.20 Zoning of concretes in high dams (H100 m)
