(iv) Silt Load The construction of a dam across a river carrying sediment invariably results in reservoir sedimentation which causes an additional force (Ws) on the upstream face of the dam. The horizontal silt pressure is assumed equivalent to a hydrostatic load exerted by a fluid with a
GRAVITY DAMS
537
mass density of 1360 kg/m3. The vertical silt pressure is assumed equivalent to that exerted by a soil with a wet density of 1925 kg/m3.
h
h¢
r gh¢
rgh
rg (h¢ + h – h¢) 3
Fig. 16.2Modification in uplift force due to drain
(v) Ice Pressure If the designer anticipates the formation of an ice sheet of appreciable thickness and its remaining on the reservoir water surface for a long duration, the ice pressures must be computed using a suitable method of their estimation. In the absence of such a method, ice pressure may be taken as 250 kPa (250 kN/m2) applied over the anticipated area of contact of ice with the face of the dam (2).
