A hydro-mechanical model for compound slow-moving rockslides with pre-existing open fractures

This paper presents a model for a unified hydro-mechanical analysis of the behaviour of compound slow-moving rockslides in the pre-failure and post-failure phases. The rockslide is described through several interacting blocks, separated by pre-existing open fractures, which move on an inclined surface. Each block is assumed to be rigid, and the fracture network is composed of vertical fractures which communicate through the basal fractures. Several key features are incorporated in the model, such as the storage of water within the fractures, viscosity and shear strength along the sliding surfaces, as well as the temporal diffusion of water pressure at the base of the landslide bodies. Moreover, the water-squeezing effect, due to the balance of the volume of water when the fractures change their apertures, is accounted for. Following the presentation of the model and its analytical formulation, a sensitivity analysis is conducted to assess how variations in different parameters influence the model's outcomes. The results of 125 simulations across 9 different scenarios, including single- and multi-block systems, were analysed and discussed. Furthermore, the model has been applied to analyse the displacement patterns associated with rainfall for a complex rockslide that occurred in the Northern Apennines in Italy, for which the model parameters were calibrated through a back analysis procedure applied to the monitoring data. The analysis of the obtained results proves that realistic simulations of slow-moving rockslide displacements can be obtained with the presented model.