Quantitative characterization of the excavation damaged zone fracture network in the Meuse/Haute-Marne Underground Research Laboratory:in situexperiment and numerical interpretation of helium injection test

2016 ◽  
Vol 443 (1) ◽  
pp. 85-96 ◽  
Author(s):  
Hua Shao ◽  
Sebastian Göthling ◽  
Wenting Liu ◽  
Jürgen Hesser ◽  
Jacques Morel ◽  
...  
Keyword(s):  
Fracture Network ◽  
Quantitative Characterization ◽  
Injection Test ◽  
Excavation Damaged Zone ◽  
Damaged Zone

Characterization of Excavation Damaged Zone and its structural heterogeneities with Time and Spectral IP methods

2012 ◽  
Author(s):  
Gonca Okay ◽  
Philippe Cosenza ◽  
Ahmad Ghorbani ◽  
Christian Camerlynck ◽  
Justo Cabrera ◽  
...  
Keyword(s):  
Excavation Damaged Zone ◽  
Damaged Zone ◽  
Structural Heterogeneities

scholarly journals Mechanical and hydraulic properties of the excavation damaged zone (EDZ) in the Opalinus Clay of the Mont Terri rock laboratory, Switzerland

Solid Earth ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1581-1600
Author(s):  
Sina Hale ◽  
Xavier Ries ◽  
David Jaeggi ◽  
Philipp Blum
Keyword(s):  
Actual State ◽  
Fracture Aperture ◽  
Near Surface ◽  
Mechanical Fracture ◽  
Excavation Damaged Zone ◽  
Rock Laboratory ◽  
Hydraulic Aperture ◽  
Damaged Zone ◽  
Mont Terri

Abstract. Construction of cavities in the subsurface is always accompanied by excavation damage. Especially in the context of deep geological nuclear waste disposal, the evolving excavation damaged zone (EDZ) in the near field of emplacement tunnels is of utmost importance concerning safety aspects. As the EDZ differs from the intact host rock due to enhanced hydraulic transmissivity and altered geomechanical behavior, reasonable and location-dependent input data on hydraulic and mechanical properties are crucial. Thus, in this study, a hydromechanical characterization of an EDZ in the Mont Terri underground rock laboratory, Switzerland, was performed using three different handheld devices: (1) air permeameter, (2) microscopic camera and (3) needle penetrometer. The discrete fracture network (DFN), consisting of artificially induced unloading joints and reactivated natural discontinuities, was investigated by a portable air permeameter and combined microscopic imaging with automatic evaluation. Geomechanical and geophysical characterization of the claystone was conducted based on needle penetrometer testing at the exposed rock surface. Within the EDZ, permeable fractures with a mean hydraulic aperture of 84 ± 23 µm are present. Under open conditions, self-sealing of fractures is suppressed, and cyclic long-term fracture aperture oscillations in combination with closure resulting from convergence processes is observed. Based on measured needle penetration indices, a uniaxial compressive strength of 30 ± 13 MPa (normal to bedding) and 18 ± 8 MPa (parallel to bedding) was determined. Enhanced strength and stiffness are directly related to near-surface desaturation of the claystone and a sharp decrease in water content from 6.6 wt % to 3.7 wt %. The presented methodological approach is particularly suitable for time-dependent monitoring of EDZs since measurements are nondestructive and do not change the actual state of the rock mass. This allows for a spatially resolved investigation of hydraulic and mechanical fracture apertures, fracture surface roughness, and physico-mechanical rock parameters and their intra-facies variability.

Characterization of the flow for a single fluid in an excavation damaged zone

2004 ◽  
Vol 332 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Brahim Amaziane ◽  
Alain Bourgeat ◽  
Mariya Goncharenko ◽  
Leonid Pankratov
Keyword(s):  
Excavation Damaged Zone ◽  
Damaged Zone

scholarly journals Mechanical and hydraulic properties of the excavation damaged zone (EDZ) in the Opalinus Clay of the Mont Terri Rock Laboratory, Switzerland

2021 ◽  
Author(s):  
Sina Hale ◽  
Xavier Ries ◽  
David Jaeggi ◽  
Philipp Blum
Keyword(s):  
Actual State ◽  
Near Surface ◽  
Mechanical Fracture ◽  
Excavation Damaged Zone ◽  
Needle Penetration ◽  
Rock Laboratory ◽  
Hydraulic Aperture ◽  
Damaged Zone ◽  
Mont Terri

Abstract. Construction of cavities in the subsurface is always accompanied by excavation damage. Especially in the context of deep geological nuclear waste disposal, the evolving excavation damaged zone (EDZ) in the near field of emplacement tunnels is of utmost importance concerning safety aspects. As the EDZ differs from the intact host rock due to enhanced hydraulic transmissivity and altered geomechanical behavior, reasonable and location-dependent input data on hydraulic and mechanical properties is crucial. Thus in this study, a hydro-mechanical characterization of an EDZ in the Mont Terri underground rock laboratory, Switzerland, was performed using three different handheld devices: (1) air permeameter, (2) microscopic camera and (3) needle penetration test. The discrete fracture network (DFN), consisting of artificially induced unloading joints and reactivated natural discontinuities, was investigated by a portable air permeameter as well as combined microscopic imaging with automatic evaluation. Geomechanical and geophysical characterization of the claystone was conducted based on needle penetrometer testing at the exposed rock surface. Within the EDZ, permeable fractures with a mean hydraulic aperture of 84 ± 23 µm are present. Under open conditions, self-sealing of fractures is suppressed and cyclic long-term fracture aperture oscillations in combination with closure resulting from convergence processes, is observed. Based on measured needle penetration indices, a uniaxial compressive strength of 30 ± 13 MPa (normal to bedding) and 18 ± 8 MPa (parallel to bedding) was determined. Enhanced strength and stiffness is directly related to near-surface desaturation of the claystone and a sharp decrease in water content from 6.6 wt.-% to 3.7 wt.-%. The presented methodological approach is particularly suitable for time-dependent monitoring of EDZs since measurements are nondestructive and do not change the actual state of the rock mass. This allows for a spatially resolved investigation of hydraulic and mechanical fracture apertures, fracture surface roughness as well as physico-mechanical rock parameters and their intra-facies variability.

scholarly journals Comparison of DFN Modelled Microfracture Systems with Petrophysical Data in Excavation Damaged Zone

2021 ◽  
Vol 11 (7) ◽  
pp. 2899
Author(s):  
Risto Kiuru ◽  
Dorka Király ◽  
Gergely Dabi ◽  
Lars Jacobsson
Keyword(s):  
Geophysical Methods ◽  
Fracture Network ◽  
Rock Types ◽  
Excavation Damaged Zone ◽  
Macro Scale ◽  
Damaged Zone ◽  
Discrete Fracture ◽  
Disturbed Layer ◽  
The Difference ◽  
Excavation Damage

Physical and petrographic properties of drill core specimens were determined as a part of investigations into excavation damage in the dedicated study area in the ONKALO® research facility in Olkiluoto, Western Finland. Microfractures in 16 specimens from two drillholes were analysed and used as a basis for fractal geometry-based discrete fracture network (DFN) modelling. It was concluded that the difference in resistivity between pegmatoid granite (PGR) and veined gneiss (VGN) specimens of similar porosity was likely due to differences in the types of microfractures. This hypothesis was confirmed from microfracture analysis and simulation: fractures in gneiss were short and mostly in one preferred orientation, whereas the fractures in granite were longer and had two preferred orientations. This may be due to microstructure differences of the rock types or could suggests that gneiss and granite may suffer different types of excavation damage. No dependencies on depth from the excavated surface were observed in the geometric parameters of the microfractures. This suggests that the excavation damaged zone cannot be identified based on the changes in the parameters of the microfracture networks, and that the disturbed layer observed by geophysical methods may be caused by macro-scale fractures.

scholarly journals The Numerical Simulation of Hard Rocks for Tunnelling Purposes at Great Depths: A Comparison between the Hybrid FDEM Method and Continuous Techniques

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Nicholas Vlachopoulos ◽  
Ioannis Vazaios
Keyword(s):  
Numerical Models ◽  
Fracture Initiation ◽  
Fracture Network ◽  
Complex Nature ◽  
Underground Opening ◽  
Hard Rocks ◽  
Excavation Damaged Zone ◽  
Damaged Zone ◽  
Stress Changes ◽  
Element Method

Tunnelling processes lead to stress changes surrounding an underground opening resulting in the disturbance and potential damage of the surrounding ground. Especially, when it comes to hard rocks at great depths, the rockmass is more likely to respond in a brittle manner during the excavation. Continuum numerical modelling and discontinuum techniques have been employed in order to capture the complex nature of fracture initiation and propagation at low-confinement conditions surrounding an underground opening. In the present study, the hybrid finite-discrete element method (FDEM) is used and compared to techniques using the finite element method (FEM), in order to investigate the efficiency of these methods in simulating brittle fracturing. The numerical models are calibrated based on data and observations from the Underground Research Laboratory (URL) Test Tunnel, located in Manitoba, Canada. Following the comparison of these models, additional analyses are performed by integrating discrete fracture network (DFN) geometries in order to examine the effect of the explicit simulation of joints in brittle rockmasses. The results show that in both cases, the FDEM method is more capable of capturing the highly damaged zone (HDZ) and the excavation damaged zone (EDZ) compared to results of continuum numerical techniques in such excavations.

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