Dams and Reservoirs - Hydrogeology: Objectives, Methods, Applications - page 291

P-push from the dam, H-hydrostatic pressure, R-resultant of the pressure
Figure 136 Malpasset dam (Var). Conditions leading to the failure of the left bank support
(from Bellier, 1967).
2.3 Prevention and treatment
In order to avoid the aforementioned problems, the best guarantee
is to proceed with a careful and complete study of the structural and
hydrogeologic conditions on a dam site beginning with its design, in
order to, on the one hand, discard sites that appear too dangerous or too
constraining, and on the other hand, to plan for the most appropriate
construction designs.
In order to effectively fi ght infi ltration underneath the dam, various
arrangements are now used on most construction sites:
• emplacement of an impermeable coating in continuity over the
upstream dam facing, along the bottom of the reservoir (small earthen
dams and hillside reservoirs);
• consolidation-cementation injections, intended to reestablish the
surface continuity of a rock mass shaken by the construction, and to
ensure an impermeable connection between the bottom of the dam
and its foundation. They are done with the help of short boreholes
(a few meters deep);
• creation of a waterproof screen prolonging the upstream facing, either
a cutoff consisting of a concrete wall or of sheet piling (unconsolidated
terrain), or a grout curtain extending to an impermeable horizon or to a
depth allowing an adequate increase in the distance that groundwater
circulations would have to cover (rocky terrain).