ABSTRACT

The paper describes the application of both continuum and discontinuum modelling to the study of the stability conditions of the Alpetto mine, a high rock cut located in Cesana Brianza (Italy). The main objective is to provide valuable information for future mine planning and for the assessment of the stability conditions of the abandoned high rock cuts. Continuum modelling involved the applications of the finite difference method, whereas the distinct element method was used for discontinuum modelling.

RESUME

L'article decrit l'application des methodes de modelisation continue/discontinue pour l'etude des conditions de stabilite de la mine d'Alpetto, situee à Cesana Brianza (Italie). Le but du travail consiste à determiner des paramètres utiles vis-à-vis du projet et d'estimer les conditions de stabilite de l'amas rocheux au terme de l'exploitation de la mine susmentionnee. La modelisation continue a implique l'application de la methode des differences finis alors que la methode des elements distincts a ete utilisee pour la modelisation discontinue.

KURZFASSUNG

Der Artikel beschreibt die Verwendung der Modellierung von continuum und discontinuum zur Untersuchung/Studium der Stabilitatsbedingungen von der Alpetto Mine, hohe Aushubsfront in einer Felsmasse die sich in der Gemeinde von Cesana Brianza befindet. Das Hauptziel dieser Arbeit ist die Festlegung von Parametern die zur Planung nuetzlich/behilflich sein können sowie auch die Möglichkeit zur Analyse/Auswertung der Stabilitat der Felsmasse-Front nach Aufhebung der Nutzung derselben. Die continuum Methode/Analyse wurde verwendet durch Unterstuetzung der Finite Differenz Methode da man fuer die Analyse der discontinuum (Fels als discontinuum beschrieben) der Distinct Elemente Methode verwendet hat.

Introduction

Rock slope stability covers a wide area in geomechanics from geological, geomorphological and hydro-geological characterization to the assessment of strength-deformability properties of the rock mass and discontinuities at different scale. Of great relevance are both the understanding of external forces (i.e. groundwater influence, seismicity, external loading) and stabilization measures (i.e. drainage, reinforcement, anchoring, etc.) when applied in order to prevent and/or control instability from developing.

By restricting to modern numerical modelling methods, one should recognize that he has the option to choose between equivalent continuum and discontinuum procedures. However, when dealing with rock slopes, the importance of discontinuities and description of their characteristics in controlling the relevant physical and mechanical processes points out the role of discontinuum modelling.

Continuum Modelling

The use of continuum modelling in slope engineering leads to the representation of the constitutive equations of the rock mass comprised of the discontinuities and rock material properties by using the empirical equations given by Hoek and Brown (1997) in order to obtain the rock mass properties of the equivalent continuum. However, great care is required, as clearly stated by the proponents of such equations: even rock masses which appear to be good candidates for the application of equivalent continuum modelling may be intercepted by discontinuities controlling stability conditions.

Continuous formulations based on the finite element method (FEM) and the finite difference method (FDM) should therefore be considered restrictive in their applicability to the analysis of rock slopes. However, there are obvious cases where, to some extent.

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