Abstract.During a risk assessment procedure as well as when dealing with cleanup and monitoring strategies, accurate predictions of solute propagation in fractured rocks are of particular importance when assessing exposure pathways through which contaminants reach receptors.Experimental data obtained under controlled conditions such as in a laboratory allow to increase the understanding of the fundamental physics of fluid flow and solute transport in fractures.In this study, laboratory hydraulic and tracer tests have been carried out on an artificially created fractured rock sample. The tests regard the analysis of the hydraulic loss and the measurement of breakthrough curves for saline tracer pulse inside a rock sample of parallelepiped shape (0.60 × 0.40 × 0.08 m). The convolution theory has been applied in order to remove the effect of the acquisition apparatus on tracer experiments.The experimental results have shown evidence of a nonDarcy relationship between flow rate and hydraulic loss that is best described by Forchheimer's law. Furthermore, in the flow experiments both inertial and viscous flow terms are not negligible.The observed experimental breakthrough curves of solute transport have been modeled by the classical onedimensional analytical solution for the advection-dispersion equation (ADE) and the single rate mobile-immobile model (MIM). The former model does not properly fit the first arrival and the tail while the latter, which recognizes the existence of mobile and immobile domains for transport, provides a very decent fit.The carried out experiments show that there exists a pronounced mobile-immobile zone interaction that cannot be neglected and that leads to a non-equilibrium behavior of solute transport. The existence of a non-Darcian flow regime has showed to influence the velocity field in that it gives rise to a delay in solute migration with respect to the predicted value assuming linear flow. Furthermore, the presence of inertial effects enhance non-equilibrium behavior. Instead, the presence of a transitional flow regime seems not to exert influence on the behavior of dispersion. The linear-type relationship found between velocity and dispersion demonstrates that for the range of imposed flow rates and for the selected path the geometrical dispersion dominates the mixing processes along the fracture network.

Abstract. The knowledge of flow phenomena in fractured rocks is very important for groundwater resources management in hydrogeological engineering.A critical emerging issue for fractured aquifers is the validity of the Darcian-type "local cubic law", which assumes a linear relationship between flow rate and pressure gradient to accurately describe flow patterns.Experimental data obtained under controlled conditions such as in a laboratory increase our understanding of the fundamental physics of fracture flow and allow us to investigate the presence of non-linear flow inside fractures that generates a substantial deviation from Darcy's law.In this study the presence of non-linear flow in a fractured rock formation has been analyzed at bench scale in laboratory tests. The effects of non-linearity in flow have been investigated by analyzing hydraulic tests on an artificially created fractured rock sample of parallelepiped (0.60 × 0.40 × 0.8 m) shape.The volumes of water passing through different paths across the fractured sample for various hydraulic head differences have been measured, and the results of the experiments have been reported as specific flow rate vs. head gradient. The experimental results closely match the Forchheimer equation and describe a strong inertial regime. The results of the test have been interpreted by means of numerical simulations. For each pair of ports, several steady-state simulations have been carried out varying the hydraulic head difference between the inlet and outlet ports. The estimated linear and non-linear Forchheimer coefficients have been correlated to each other and respectively to the tortuosity of the flow paths.A correlation among the linear and non-linear Forchheimer coefficients is evident. Moreover, a tortuosity factor that influences flow dynamics has been determined.

The knowledge of flow phenomena in fractured rocks is very important for groundwater resources management in hydrogeologic engineering. <br><br> A critical emerging issue for fractured aquifers is the validity of the Darcian-type "local cubic law" which assumes a linear relationship between flow rate and pressure gradient to accurately describe flow patterns. <br><br> Experimental data obtained under controlled conditions such as in a laboratory allow to increase the understanding of the fundamental physics of fracture flow and to investigate the presence of non linear flow inside the fractures which brings to substantial deviation from Darcy's law. <br><br> In this study the presence of non linear flow in a fractured rock formation has been analyzed at bench scale in laboratory tests. The effects of non linearity in flow have been investigated by analyzing hydraulic tests on artificially created fractured rock samples of parallelepiped (0.60 &times; 0.40 &times; 0.8 m) shape. <br><br> The volumes of water passing through different paths across the fractured sample for various hydraulic head differences have been measured, and the results of the experiments have been reported as flow rate/specific discharge vs. head gradient. The experimental results closely match the Forchheimer equation and describe a strong inertial regime. Successively the results of the test have been interpreted by means of numerical simulations. For each pair of ports several steady-state simulations have been carried out varying the hydraulic head difference between inlet and outlet ports. The estimated linear and non linear Forchheimer coefficients have been correlated to each other and, respectively to the tortuosity of the flow paths. A correlation among the linear and non linear Forchheimer coefficients is evident. Moreover, a tortuosity factor has been determined that influences flow dynamics

Fluid flow and solute transport phenomena in\ud fractured and karstic aquifers remain an open issue that\ud calls the attention of numerous researchers belonging to\ud different disciplinary fields as far as the aspects linked both\ud to shallow and to deep phenomena are concerned. The\ud hydrogeologic knowledge of these phenomena proves to be\ud of high importance especially if considered in relationship\ud with water resource exploitation, with the problems linked\ud to contamination and the ones linked to urban and industrial\ud development of the territory. In the examined area,\ud characterized by a dismissed contaminated site, the realization\ud of the landfill has required the development of a 3D\ud flow model supported by a detailed local scale geologic\ud model in order to evaluate the effects on groundwater flow\ud and subsequently on contaminant propagation. The results\ud of the flow model prove to be coherent with the fractured\ud and karstic nature of the site in that they show at higher\ud depths the presence of a subterranean stream channel that\ud would speed up pollutant propagation. The obtained results\ud represent the fundamental basis to implement a transport\ud model that will permit to achieve a more in depth knowledge\ud of the subsoil transport phenomena, and therefore to\ud optimize any anthropic intervention that can involve the\ud site