Modeling fracture flow with a stochastic discrete fracture network: calibration and validation: 1. The flow model

Abstract

A large‐scale investigation of fracture flow was recently conducted in a granite uranium mine at Fanay‐Augères, France. Its aim was to develop a methodology for the investigation of possible nuclear waste repository sites in crystalline environments, and thus to determine what measurements to make and what models to use in order to predict the flow and transport properties of the medium, i.e., their average behaviors and spatial variabilities at different scales. Four types of data were collected: (1) geometry of the fracture network; (2) local hydraulic properties measured by injection tests in boreholes; (3) global hydraulic behavior from flow rate and piezometric head distribution at a 106 m3 scale; and (4) tracer tests performed at a scale of up to 40 m. A stochastic fracture network model assuming negligible matrix permeability was developed and calibrated essentially on data 1 and 2 above; this was then used to predict data 3 and 4 in an attempt to validate both the parameters and the structure of the model. In this first part, only the flow problem (data 1) is discussed.

Characteristics of Block Hydraulic Conductivity of 2-D DFN System According to Block Size and Fracture Geometry

“…DFN 기반의 유체유동을 모사하기 위한 수치해석기법으 로는 유한요소법(FEM; finite element method) (Herbert, 1996, Wilcock, 1996, 경계요소법(BEM; boundary element method) (Elsworth, 1986a,b), 등가파이프모델(EPM; equivalent pipe model) (Cacas et al, 1990a (Diodato, 1994 …”

Water Inrush Analysis of the Longmen Mountain Tunnel Based on a 3D Simulation of the Discrete Fracture Network

“…The basic research idea is to obtain the field structure fracture data then use a large number of experiments to verify these data. By analysing the parameters of the fracture, we have been able to make several conclusions: the crack openings follow a log-normal distribution [10], the crack length follows a power law distribution [21], and the fracture attitude follows a Fisher distribution [22], a Bingham distribution and so on. Based on the premises above, the three-dimensional discrete network model of the Longmen Mountain area was simulated using the Monte Carlo simulation method and was transferred to the network model.…”

“…Noetinger [18] analysed the percolation model for three-dimensional fracture networks and proposed the use of the Darcy flow equation in threedimensional fracture networks. Furthermore, to make the discrete fracture simulation become more efficient in the simulation, Cacas [10] proposed a method in which the crack is replaced with a conduit, thereby reducing the group number required to solve the equation by an order of magnitude. Dershowitz [19] proposed an optimization model that the polygonal fracture network was transformed into an approximate equivalent three-dimensional network consisting of a one-dimensional pipeline.…”

“…To establish a reasonable fracture network, we first need to determine a three-dimensional fracture network model. With the on-going efforts of international scholars, the disk fracture network model [8], the polygonal fracture network model [9] and the circular pipe model [10] have been proposed in the past few years. AӔer the fracture network model is constructed, then we should use the fracture networks model to simulate fracture distribution of the tunnel site.…”

Upscaling of a dual-permeability Monte Carlo simulation model for contaminant transport in fractured networks by genetic algorithm parameter identification

“…These methods do not rely on volume averaging techniques, but solve the flow and transport problem in individual fractures by accounting for both anisotropy and stochasticity [13] [14]. Nevertheless, an important drawback of these methods is related to the high degree of complexity of the modeling which requires an intensive computational effort and thus limits their range of applicability to near-field scales [6] [7][14] [5], and actually prevents the use in the probabilistic uncertainty and sensitivity analyses required in the PA of radioactive waste repositories.…”