Investigations carried by the Geodynamic Research Center at such dams as the 270 m high Inguri arch dam (Georgia), the 245 m high Sayano-Shushenskaya arch-gravity dam (Russia) and 110 m high Capanda gravity dam (Angola) show that after impoundment of the reservoir and in seasonal fluctuations of its water stages there takes place uplifting of the shore rock masses, vertical tensioning of the dam body accompanied by cracking and opening of the construction joints at the upstream face, development of new seepage paths and increases in the seepage flows.
At the same time there occurs de-stressing of the rock mass due to opening of the joints and drop in its shear strength due to uplift of the vertical stresses in the rock mass which has been confirmed by geophysical explorations which were conducted in filling the Inguri and Sayano- Shushenskaya reservoirs.
Sharp changes of the seepage pattern in the foundation lead to jump-like head variations, breakthrough of the plugged holes, development of new seepage paths, seepage flow increases.
These impacts are most distinctly displayed at high reservoir levels when horizontal loads tend to rise significantly in the dam abutments, which entail decrease in safety of the whole dam-foundation system.
The "dam-foundation- reservoir" system is a complex but indivisible interacting entity. Creation of a reservoir leads not only to the surcharging of the local areas in the Earth crust but concurrently changes the hydro geological conditions in the zone of its influence. In filling the reservoir created by a high dam, complex deformation processes are triggered in its rock foundation. First, the weight of placed concrete and water accumulated in the reservoir causes settlement of the reservoir bottom and dam abutments and concurrently as water penetrates into joints of the rock mass there takes place its saturation with water and uplifting which is accompanied by opening of the joints and rise of the foundation and abutments. At the same time there occurs de-stressing of the rock mass due to opening of the joints and degradation of its shear strength properties. This has been proved by a complex of geophysical explorations conducted in impoundment of the Ingouri reservoir.
At the same time vertical compression stresses drop in the dam body, that contributes to penetration of the water into the construction joints and uplifting of the dam body. As this takes place, the effect of uplifting tends to increase with increment in the height of the dam section.
Investigations carried by the Geodynamic Research Center at such dams as the Ingouri arch dam (Georgia), Sayano-Shushenskaya arch-gravity dam (Russia), Capanda gravity dam (Angola) have shown that after filling of the reservoir and during seasonal fluctuations of its level there takes place lifting of the bank rock masses in the upstream and downstream zones, increase in the dam height accompanied by cracking and opening of the construction joints at the upstream face, development of new seepage paths and increase in seepage flows.