(a) Primary loads
- Water load.This is a hydrostatic distribution of pressure with hori-
zontal resultant force P 1. (Note that a vertical component of load will
also exist in the case of an upstream face batter, and that equivalent
tailwater loads may operate on the downstream face.) - Self-weight load.This is determined with respect to an appropriate
unit weight for the material. For simple elastic analysis the resultant,
P 2 , is considered to operate through the centroid of the section. - Seepage loads.Equilibrium seepage patterns will develop within and
under a dam, e.g. in pores and discontinuities, with resultant vertical
loads identified as internal and external uplift, P 3 andP 4 , respec-
tively. (Note that the seepage process will generate porewater pres-
sures in pervious materials, and is considered in this light as a
derivative of the water load for the embankment dam (Section
1.7.3).)
(b) Secondary loads
- Sediment load.Accumulated silt etc. generates a horizontal thrust,
considered as an equivalent additional hydrostatic load with horizon-
tal resultant P 5. - Hydrodynamic wave load.This is a transient and random local load,
P 6 , generated by wave action against the dam (not normally signific-
ant). - Ice load.Ice thrust, P 7 , from thermal effects and wind drag, may
develop in more extreme climatic conditions (not normally signific-
ant). - Thermal load (concrete dams).This is an internal load generated by
temperature differentials associated with changes in ambient con-
ditions and with cement hydration and cooling (not shown). - Interactive effects.These are internal, arising from differential defor-
mations of dam and foundation attributable to local variations in
foundation stiffness and other factors, e.g. tectonic movement (not
shown). - Abutment hydrostatic load.This is an internal seepage load in the
abutment rock mass, not illustrated. (It is of particular concern to
arch or cupola dams.)
(c) Exceptional loads
- Seismic load.Oscillatory horizontal and vertical inertia loads are
generated with respect to the dam and the retained water by seismic
disturbance. For the dam they are shown symbolically to act through
the section centroid. For the water inertia forces the simplified