Abstract

The first step to determine mechanical and hydraulic properties of rock masses is the evaluation of geometrical characterizations of discontinuities. Discrete Fracture Network models have been developed to model the geometrical properties of discontinuities. Among all the discontinuity properties, shape is the most controversial. In previous Discrete Fracture Network models, discontinuities were considered as planar surfaces while in some fields, curve-shaped discontinuities could be observed. Folding is the most common factor in the creation of curve-shaped discontinuities in mines and engineering works. In this research, a practical 3D geometrical method has been introduced to model folded layers using Fourier analysis and Spline function. Based on the proposed method, a practical MATLAB script named RocFold was developed. Finally, to evaluate the applicability and the feasibility of the proposed model and script, a typical folded structure in Anjire lead and zinc mine in Isfahan province, Iran was applied.

1 Introduction

Discrete Fracture Network (DFN) models have been developed to model the geometrical properties of discontinuities by statistical values and distributions of these characteristics evaluated from analysis of core logging and outcrops mapping. Different conceptual models are applied to build DFN models, and each of them is based on specific relationships between characteristics such as location of fracture, termination, and fracture shape. The earliest model developed to represent fracture systems was based upon the assumption that all fractures can be defined by three sets of unbounded orthogonal fractures (Dershowitz & Einstein 1988). The basic model defined by Snow (1965) consists of orthogonal sets of parallel-unbounded fractures, with a constant spacing between the fractures within each set. Baecher disk model (disk-shaped discontinuities) has been developed by Baecher et al. (1977) and Barton (1978) simultaneously and was one of the first well-characterized discrete fracture models. The ordinary Baecher model has been further on developed to account for fracture terminations at intersections with pre-existing fractures and for more general fracture shapes (Geier et al. 1989 and Dershowitz et al. 1998). Veneziano (1978) introduced a method for adaptation of the concept of Poisson plane fractures to bounded fractures (Veneziano model). Dershowitz (1984) remedied the disadvantage of the Veneziano model that fracture intersections and fracture edges do not coincide. Other than the mentioned models, some other practical conceptual models have been proposed for the modeling of fracture network, such as geostatistical and fractal models.

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