ABSTRACT

ABSTRACT:

On March 12, 2005 in the Scascoli Gorges (Savena Valley, Northern Apennines, Italy) a rock slope failure involving siltstones and arenites occurred damming the torrent below. The geometry of the collapsed rock mass was characterized by a failure surface progressively changing from over-steepened at the top to concave at the bottom. Terrestrial laser scanner technique (TLS) has been applied to obtain high resolution topography of the rock slope. Mechanism and kinematics of the rock slope failure has been investigated by distinct-element modelling (UDEC). As distinct element simulations in rock masses largely depends on joint pattern and orientation, accurate discontinuities orientation, spacing and location of discrete surface features have been directly gathered from data provided by TLS. This paper describes the stability analyses carried out on simulating the progressively developing damage of the rock mass by reducing the GSI initial value and using a Hoek & Brown constitutive model.

1 INTRODUCTION

Mass movements represent a significant hazard in the Italian Apennines, where different lithologies outcrop even in complex structural settings. In such rock masses, generally characterized by a dense network of discontinuities producing a blocky structure, simulation of instability processes can be carried out with discontinuous models by introducing joint systems into the numerical simulation using finite element or distinct element approaches (e.g. Goodman et al. 1968). Discontinuous modelling has been developed and implemented leading to more detailed and reliable geomechanical models for slope stability analyses, especially with respect to back-analyses and the verification of both the correctness of assumed soil or rock model parameters and constitutive models. However weathering affects the shear strength of discontinuities due to the weakening of the asperities, and the reduction of the base friction angle as a result of possible changes in mineralogy.

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