Análise numérica bidimensional e tridimensional de estabilidade de talude de grande altura em mina a céu aberto

Two-dimensional and three-dimensional numerical analysis of high slope stability in open pit mine

Abstract

The slope stability analyzes most commonly used in geotechnical engineering practice are in two dimensions. However, the evaluation in three dimensions tends to be more rigorous, and more justifiable to represent the real condition of the geometry of the unstable terrain mass. Thus, advances in the theory of three-dimensional stability analysis, the increase in the processing power of personal computers and the development of more robust software packages, have allowed engineers, designers and researchers to present these analyzes in a more assertive and pragmatic way. In this way, the article develops the analysis of the two-dimensional and three-dimensional slope stability of a pit of an open-pit mine located within the Mineral Complex of Patrocínio-MG, with height in the order of 375m, with banks of 10m, evaluating the consistency of the database available and, in sequence, the results obtained. The geology of the region is characterized by an economic alkaline deposit of phosphate that occurs in the central area located entirely within the Salitre I dome. Rocscience®. The stability method adopted for the present research was the General Limit Equilibrium Method (GLE) proposed by Morgenstern-Price (1965) for two-dimensional problems with lamellae (slices) of 1 (one) meter thickness, later adapted for three-dimensional problems, where 2D lamellae were replaced by 3D columns, thus generalizing their use. A safety factor was then obtained with the average resistance parameters of the materials of 1.22 2D and average (FS) 1.32 3D, close to the minimum (FS) = 1.30 recommended by several authors for pit slopes, enough to define an unstable slope condition. Considering the 2D analytical model as a reference, in absolute terms, the difference between the analyzes is around 8.2%, thus showing convergence between the analyses.

Keywords: 2D and 3D stability analysis, limit equilibrium, automatic search, critical section, open pit mine.