Modeling the Hydraulic Characteristics of a Fractured Rock Mass With Correlated Fracture Length and Aperture: Application in the Underground Research Tunnel at Kaeri

Bang, Seokhwan; Jeon, Seokwon; Kwon, Soonjo

doi:10.5516/net.02.2011.026

“…In recent years, based on the previous models, stochastic model has been developed more for the purpose of investigating the effects of the correlation between the length and aperture of the joints on hydromechanical and mechanical behavior of the jointed rock mass. The two dimensional model presented by Baghbanan and Jing (2008) and the three dimensional model presented by Xu and Dowd (2010) as well as the model presented by Bang et al (2012) are some instances that support this claim.…”

Section: Literature Reviewmentioning

confidence: 70%

3D Geometrical-Stochastical Modeling of Rock mass joint networks: Case study of the Right Bank of Rudbar Lorestan Dam plant

Noroozi¹,

Kakaie²,

Jalali³

2015

J. Geol. Min. Res.

5

0

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Nowadays, modeling is increasingly used as a method for determination of the mechanical and hydraulic behavior of the rock mass. In this paper, with regard to the high importance of joint persistence characteristic on the mechanical and hydraulic behavior of the rock mass, geometricstochastic joint network model has been developed by considering the statistical characteristics of joint size based on Veneziano model. With the use of surveyed data in the right bank of Rudbar Lorestan dam plant and estimation of the best probability distribution function on geometric characteristics of existing joint sets in this region, the three-dimensional geometric model of joint network has been developed. In order to model implementation, a computer code written in C++, called FRAC3D, has been developed that is able to represent the joint network in different directions and to generate text outputs. The results of this model can be a useful input for numerical stability analysis and hydraulic behavior studies of rock mass.

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“…The presence of discontinuities such as faults and highly jointed and fractured rocks can be a significant factor in determining the groundwater inflow into tunnels and underground spaces. In a rock mass with high permeability, a large volume of water flow can occur, and since fractured rocks and discontinuities often constitute a small percentage of the surrounding area of the tunnel, higher permeability values can interfere with lower values, and the permeability value in an area will be affected by higher or lower values (Bang et al, 2012;Chen and Tonon, 2012;Fernandez and Moon, 2010).…”

Section: ()mentioning

confidence: 99%

Enhancing analytical methods for estimating water inflow to tunnels in the presence of discontinuity areas

Farhadian,

Bahmani Shahraki

2024

Environ Earth Sci

1

0

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There are various methods for calculating the inflow of water into excavated tunnels in rock formations, including empirical, analytical, and numerical methods. Analytical equations are widely used due to their simplicity and reliance on assumptions. However, past studies have shown that the measured water inflow into rock tunnels is often lower than the values estimated using analytical equations. Moreover, results obtained using analytical equations are highly dependent on the tunnel geometry and environmental conditions. Hence, this study employed finite element numerical modeling to simulate the effects of various factors, including fault distance from the tunnel, permeability coefficient, fault width, tunnel radius, rock mass permeability, and groundwater level, on the water inflow into the tunnel. The analytical method 2 was then used to estimate the water inflow, and the results were compared with the numerical modeling outputs. Subsequently, modified equations were developed to estimate the water inflow under different conditions, including cases where the fault intersects or does not intersect the tunnel. The correlation between the results obtained from the equations and the numerical modeling outputs was evaluated using R and R 2 statistics. The obtained values were within an acceptable range, indicating the validity of the proposed models. Furthermore, the histograms of the residuals for both models showed a good fit. To validate the proposed models, the analytical method and the proposed equations were used to estimate the water inflow into the Amirkabir tunnel, respectively. The results showed that the values obtained using the new equations were closer to the actual values than those obtained using the analytical method. This study highlights the importance of considering various factors in estimating the water inflow into rock tunnels and provides new equations that can improve the accuracy of such estimates.

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“…The hydraulic properties of fracture networks which constitute the main flow paths are of significant importance for fluid flow and transport in fractured rock masses with negligibly low permeability of matrix [1][2][3][4][5][6]. Natural fracture networks usually show a strong hydraulic variability which comes from the overall statistical geometry characteristics [7][8][9][10][11][12][13]. The discrete fracture network (DFN) models are conceived for modeling the spatial structures and geometric features of nat-urally fractured rocks quite well [7][8][9][10][14][15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…Natural fracture networks usually show a strong hydraulic variability which comes from the overall statistical geometry characteristics [7][8][9][10][11][12][13]. The discrete fracture network (DFN) models are conceived for modeling the spatial structures and geometric features of nat-urally fractured rocks quite well [7][8][9][10][14][15][16][17][18][19][20][21][22]. Therefore, DFN modeling is applicable for investigating the effect of geometric characteristics on the hydraulic properties in fractured rock masses.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, 3D DFN modeling is applicable for predicting the hydraulic behaviors of the natural fracture network. Bang et al [9] developed a 3D DFN model to estimate the REV of granitic rock mass at Korea Atomic Energy Research concerning the hydraulic properties. Huang et al [24] investigated the effect of power exponent on the equivalent permeability of the 3D DFN model by solving the Reynolds equation using the Galerkin method, which is consisted of fractures following power-law distribution.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigations on the Effect of Fracture Length Distribution on the Representative Elementary Volume of 3D Discrete Fracture Networks

Liu

¹

,

Pu

²

,

Guo

³

et al. 2022

Geofluids

0

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Determination of the representative elementary volume (REV) of fractured rock masses based on equivalent permeability ( K ) is significantly dependent on the geometric characteristics of fractures. In this work, a series of numerical simulations were performed to analyze the relationship between geometric characteristics of fractures and the REV size, in which fracture length follows a power-law distribution. A method to evaluate the K of a three-dimensional (3D) discrete fracture network (DFN) by extracting the equivalent pipe network (EPN) model from the DFN model was utilized and verified. The results show that K of the 3D DFN model has an exponential relationship with the power exponent ( a ) of fracture length distribution and the evaluation of K agrees well with that reported in previous studies, confirming the reliability of the EPN model for calculating seepage properties of complex 3D DFN models. When the side length of submodels ( L n ) is small, the K varies significantly due to the influence of random number seeds used to generate fracture length, location, and orientation. The K holds a constant value after L n exceeds some specific value. The critical model scale is determined as the REV size, and the corresponding volume of the 3D DFN model is represented by V REV . The V REV varies within a narrow range when a ≤ 4.0 . When a = 4.5 , the V REV rapidly increases to more than 3.4 times than that when a = 4.0 . The fluid flow becomes more inhomogeneous due to the small nonpersistent fractures that dominate the preferential flow paths when a exceeds a certain value (i.e., 4.5). The K at the REV size decreases exponentially with the increment of a . This tendency can be explained by the decrease of the average intersection length ( L i ) with the increment of a , which is a geometric parameter for reflecting the connectivity of the fracture network.

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Modeling the Hydraulic Characteristics of a Fractured Rock Mass With Correlated Fracture Length and Aperture: Application in the Underground Research Tunnel at Kaeri

Cited by 13 publications

References 17 publications

3D Geometrical-Stochastical Modeling of Rock mass joint networks: Case study of the Right Bank of Rudbar Lorestan Dam plant

3D Geometrical-Stochastical Modeling of Rock mass joint networks: Case study of the Right Bank of Rudbar Lorestan Dam plant

Enhancing analytical methods for estimating water inflow to tunnels in the presence of discontinuity areas

Numerical Investigations on the Effect of Fracture Length Distribution on the Representative Elementary Volume of 3D Discrete Fracture Networks

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