Optimization of the Geometry of Monitoring Devices for Contaminant Detection in Cement-Bentonite Cutoff Walls

Cutoff walls represent an interesting solution for the containment of the pollution of superficial groundwater. For polluted sites, the purpose of a cement-bentonite cutoff wall is to minimize contaminant transport and the primary design requirement for such materials is the low hydraulic conductivity. Despite these barriers are often cast in place as provisional tools, recently their wide use imparted the need for a better understanding of cement-bentonite walls also in the long-term. This certainly implies not only the need to study the time evolution of the cement-bentonite hydro-mechanical properties in a contaminated environment, but also the necessity of a continuous monitoring of the efficiency of the system. To this aim, the use of dedicated devices cast in place inside the wall when the mixture is still fluid proved to be particularly suitable to intercept and analyse the fluids flowing through the barrier. In this paper, the results of a numerical study are presented, with the goal of suggesting criteria about the optimum spacing and geometry of these devices.