Reinforcement of the ground by injection of cement grout for the installation of piles in karstified limestone zone

The Thies-Touba toll highway is one of the largest road projects in West Africa. It is 115 km long and is made of 2 × 2 lanes for a speed limit of 130 km / h. Indeed, the geotechnical studies carried out, in order to characterize the ground foundations of the route and the major civil engineering structure, revealed the presence of karsts (cavities of dissolution in the marno-calcareous formations) under certain overpasses of the highway. The modelling of piles in the presence of karsts has shown that these cavities influence the stability of projected crossing structures. Thus, a solution of cavity treatment by drilling, followed by an injection of cement grout was proposed and carried out up to 29 m of depth compared to the natural ground in order to fill all the voids (fractures and holes). To control the effectiveness of cavity filling at depth, 29 m test cores were taken at the axis of the pile location. They showed that the filling of cavities was well done and gives a good bearing capacity of the soil.