First experimental results on “clay and bentonite” mixtures for the waterproofing of a landfill in Northwestern Piedmont Region (NW Italy)

We report on experimental results conducted on “clay and bentonite” mixtures for the waterproofing of a tank landfill located in Northwestern Piedmont Region (NW Italy). The geotechnical experimental tests on “clay and bentonite” mixtures were conducted in the laboratory first, with the aim of finding the optimum percentage of granular bentonite to be added to the clay and then, they were carried out in situ, in the tank, on the layer of “clay and bentonite” rolled and compacted. The optimum percentage of bentonite to be added to the clay is able to guarantee values of hydraulic conductivity of 1.00 x 10 -7 cm/s as required by normative standards of specifications for the bottom of a tank for the waterproofing of the landfill. The goal of the paper is to propose a geotechnical methodology to carried out when geologists and engineers have to design a mineral barrier for the waterproofing of a tank, using clayey soils enable to guarantee the isolation of the waste and preventing the infiltration of the percolate in the subsoil. In this case, we suggest to realize an optimum mixture of “clay and bentonite” for the waterproofing of the tank. The experimental tests allow us to find not only the optimum percentage of bentonite to be added to the clay, but also to design the minimum thickness of the layer of “clay and bentonite” to lay on the bottom of the tank for the waterproofing of the landfill.