Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach
A quantitative and analytical approach is adopted to estimate two important parameters for coupled hydro-mechanical analysis at the scale of a fractured rock mass, namely the equivalent Biot effective stress coefficient α¯ and Skempton pore pressure coefficient B¯ . We derive formal expressions that estimate the two equivalent poroelastic coefficients from the properties of both the porous intact rock and the discrete fracture network, which includes fractures with different orientation, size, and mechanical properties. The coefficients are equivalent in the sense that they allow effectively predicting the volumetric deformation of the fluid-saturated fractured rock under an applied load in drained and undrained conditions. The formal expressions are validated against results from fully coupled hydro-mechanical simulations on systems with explicit representation of deformable fractures and rock blocks. We find that the coefficients are highly anisotropic as they largely vary with fracture orientations with respect to the applied stress tensor. For a given set of fracture and rock properties, B¯ increases with the ratio of normal to average stress undergone by the fractures, while the opposite occurs for α¯ . Additionally, both α¯ and B¯ increase with fracture density, which directly impacts the deformation caused by a load in undrained conditions. Because the effective stress variation is proportional to the applied load by (1 - α¯ B¯) , a factor that partly compensates for the decrease in equivalent rock stiffness caused by the fractures, a fully saturated fractured rock may deform less than an intact rock in undrained conditions, while the opposite occurs in dry conditions.
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Springer Nature
2023-12-01
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Subjects: | Skempton pore pressure coefficient, Biot coefficient, DFN, Effective stress, Fractures, Rock mass, Ensure access to affordable, reliable, sustainable and modern energy for all, |
Online Access: | http://hdl.handle.net/10261/361300 https://api.elsevier.com/content/abstract/scopus_id/85170374826 |
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dig-idaea-es-10261-3613002024-06-22T20:41:24Z Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach De Simone, Silvia Darcel, Caroline Kasani, Hossein A. Mas Ivars, Diego Davy, Philippe 0000-0002-3647-7869 Skempton pore pressure coefficient Biot coefficient DFN Effective stress Fractures Rock mass Ensure access to affordable, reliable, sustainable and modern energy for all A quantitative and analytical approach is adopted to estimate two important parameters for coupled hydro-mechanical analysis at the scale of a fractured rock mass, namely the equivalent Biot effective stress coefficient α¯ and Skempton pore pressure coefficient B¯ . We derive formal expressions that estimate the two equivalent poroelastic coefficients from the properties of both the porous intact rock and the discrete fracture network, which includes fractures with different orientation, size, and mechanical properties. The coefficients are equivalent in the sense that they allow effectively predicting the volumetric deformation of the fluid-saturated fractured rock under an applied load in drained and undrained conditions. The formal expressions are validated against results from fully coupled hydro-mechanical simulations on systems with explicit representation of deformable fractures and rock blocks. We find that the coefficients are highly anisotropic as they largely vary with fracture orientations with respect to the applied stress tensor. For a given set of fracture and rock properties, B¯ increases with the ratio of normal to average stress undergone by the fractures, while the opposite occurs for α¯ . Additionally, both α¯ and B¯ increase with fracture density, which directly impacts the deformation caused by a load in undrained conditions. Because the effective stress variation is proportional to the applied load by (1 - α¯ B¯) , a factor that partly compensates for the decrease in equivalent rock stiffness caused by the fractures, a fully saturated fractured rock may deform less than an intact rock in undrained conditions, while the opposite occurs in dry conditions. This work was funded by the Swedish nuclear fuel waste management company, Svensk Kärnbränslehantering AB (SKB), and the Nuclear Waste Management Organization (NWMO) in Toronto, Canada. The authors wish to thank Rima Ghazal for her help with the numerical models in 3DEC. Peer reviewed 2024-06-22T08:13:55Z 2024-06-22T08:13:55Z 2023-12-01 artículo Rock Mechanics and Rock Engineering 56: 8907–8925 (2023) 07232632 http://hdl.handle.net/10261/361300 10.1007/s00603-023-03515-9 2-s2.0-85170374826 https://api.elsevier.com/content/abstract/scopus_id/85170374826 en Rock Mechanics and Rock Engineering Publisher's version https://doi.org/10.1007/s00603-023-03515-9 Sí open Springer Nature |
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Skempton pore pressure coefficient Biot coefficient DFN Effective stress Fractures Rock mass Ensure access to affordable, reliable, sustainable and modern energy for all Skempton pore pressure coefficient Biot coefficient DFN Effective stress Fractures Rock mass Ensure access to affordable, reliable, sustainable and modern energy for all |
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Skempton pore pressure coefficient Biot coefficient DFN Effective stress Fractures Rock mass Ensure access to affordable, reliable, sustainable and modern energy for all Skempton pore pressure coefficient Biot coefficient DFN Effective stress Fractures Rock mass Ensure access to affordable, reliable, sustainable and modern energy for all De Simone, Silvia Darcel, Caroline Kasani, Hossein A. Mas Ivars, Diego Davy, Philippe Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach |
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A quantitative and analytical approach is adopted to estimate two important parameters for coupled hydro-mechanical analysis at the scale of a fractured rock mass, namely the equivalent Biot effective stress coefficient α¯ and Skempton pore pressure coefficient B¯ . We derive formal expressions that estimate the two equivalent poroelastic coefficients from the properties of both the porous intact rock and the discrete fracture network, which includes fractures with different orientation, size, and mechanical properties. The coefficients are equivalent in the sense that they allow effectively predicting the volumetric deformation of the fluid-saturated fractured rock under an applied load in drained and undrained conditions. The formal expressions are validated against results from fully coupled hydro-mechanical simulations on systems with explicit representation of deformable fractures and rock blocks. We find that the coefficients are highly anisotropic as they largely vary with fracture orientations with respect to the applied stress tensor. For a given set of fracture and rock properties, B¯ increases with the ratio of normal to average stress undergone by the fractures, while the opposite occurs for α¯ . Additionally, both α¯ and B¯ increase with fracture density, which directly impacts the deformation caused by a load in undrained conditions. Because the effective stress variation is proportional to the applied load by (1 - α¯ B¯) , a factor that partly compensates for the decrease in equivalent rock stiffness caused by the fractures, a fully saturated fractured rock may deform less than an intact rock in undrained conditions, while the opposite occurs in dry conditions. |
author2 |
0000-0002-3647-7869 |
author_facet |
0000-0002-3647-7869 De Simone, Silvia Darcel, Caroline Kasani, Hossein A. Mas Ivars, Diego Davy, Philippe |
format |
artículo |
topic_facet |
Skempton pore pressure coefficient Biot coefficient DFN Effective stress Fractures Rock mass Ensure access to affordable, reliable, sustainable and modern energy for all |
author |
De Simone, Silvia Darcel, Caroline Kasani, Hossein A. Mas Ivars, Diego Davy, Philippe |
author_sort |
De Simone, Silvia |
title |
Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach |
title_short |
Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach |
title_full |
Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach |
title_fullStr |
Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach |
title_full_unstemmed |
Equivalent Biot and Skempton Poroelastic Coefficients for a Fractured Rock Mass from a DFN Approach |
title_sort |
equivalent biot and skempton poroelastic coefficients for a fractured rock mass from a dfn approach |
publisher |
Springer Nature |
publishDate |
2023-12-01 |
url |
http://hdl.handle.net/10261/361300 https://api.elsevier.com/content/abstract/scopus_id/85170374826 |
work_keys_str_mv |
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