AMMASSI ROCCIOSI FRATTURATI: MODELLAZIONE DEL RETICOLO DI FRATTURAZIONE, EFFETTI SULLA CIRCOLAZIONE IDRICA E SULLA STABILITÀ.

Rock joint characterization is a very complex task due to the heterogeneity and spatial variability of the fracture parameters. This PhD thesis is aimed to model a discrete fracture network and assess the effects of fracture properties on fluid flow and rock mass stability. Data were collected on a quartz rock mass well exposed both on surface and underground, along a well developed network of mining tunnels. A large number of structural and geomechanical data were collected and analysed by statistical procedures. Distribution and probability density function of fracture parameters were derived from row data. Geostatistical interpolation methods were used to reproduce the spatial variability of the rock features, such as the variation of fracture spacing, aperture and orientation. A stochastic simulation of the discrete fracture network was then developed using FracMan software package, and a flow model, based on the dual porosity approach, was developed to assess the water inflow into the tunnel system. A review of the fracture permeability assessment is also discussed and applied for the definition of the model properties. The fracture parameters were validated using backfitting methods until the obtained results were consistent with the hydrogeological and mechanical conditions of the study site. Block stability was then evaluated considering the blocks defined by the intersections between the discrete fracture network and the tunnels. Kinematics of instability were analyzed for the identified blocks; the factor of safety and the volume of stable and unstable blocks were also evaluated.