Prediction of water inflow into underground excavations in fractured rocks using a 3D discrete fracture network (DFN) mo
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ORIGINAL PAPER
Prediction of water inflow into underground excavations in fractured rocks using a 3D discrete fracture network (DFN) model E. Karimzade 1 & M. Sharifzadeh 2 & H. R. Zarei 3 & K. Shahriar 4 & M. Cheraghi Seifabad 1
Received: 28 June 2016 / Accepted: 18 April 2017 # Saudi Society for Geosciences 2017
Abstract Groundwater flow is a major issue in underground opening in fractured rocks. Because of finding the fracture connectivity, contribution of each fracture in flow, and fracture connectivity to excavation boundary, the prediction of water flow to underground excavations is difficult. Simulation of fracture characteristics and spatial distribution is necessary to obtain realistic estimation of inflow quantity to tunnel and underground excavations. In this research, a computer code for three-dimensional discrete fracture network modeling of water inflow into underground excavations was developed. In this code, the fractures are simulated as ellipsoid while geometrical properties of the fractures are reproduced using a stochastic method. Properties such as the size, orientation, and density of the fractures are modeled by their respective probability distributions, which are obtained from field measurements. According to the fracture condition, the flow paths in rock mass are determined. The flow paths are considered as channels with rectangular sections in which channel width and fracture aperture determine geometry of channel section. Inflow into excavation is predicted ignoring matrix permeability and considering the hydrogeological conditions. To verify presented model, simulation results were compared to a part of the Cheshmeh-
* M. Cheraghi Seifabad [email protected] 1
Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran
2
Department of Mining and Metallurgy Engineering, Western Australian School of Mines, Curtin University, Kent St., Bentley, WA 6102, Australia
3
Mahab Ghods Consulting Engineering Company, Tehran, Iran
4
Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran
Roozieh water transfer tunnel in Iran. The results obtained from this research are in good agreement with the field data. Thus, the average of the predicted inflow has just an approximation error equal to 17.8%, and its standard deviation is 8.6 l/s, which is equal to 21% of the observed value that demonstrates low dispersion of the predicted values. Keywords Water inflow . Underground excavations . Fractured rock . 3D DFN models
Introduction The proper evaluation of fluid flow behaviors in fractured rocks is of important issues in numerous geoscientific fields, such as tunneling within aquifers (Butscher et al. 2011; Zarei et al. 2013), water resource management (Dagan and Neuman 2005; Folch et al. 2011), contaminant migration and nuclear waste isolation (Hyman et al. 2015; Qian et al. 2011; Gellasch et al. 2013), geothermal energy extraction (Kohl et al. 1995; Bruel 1995), and hydrocarbon exploitation (Karra et al. 2015). When an un
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