Stress-dependent Flow in Fractured Rocks at Sellafield, United Kingdom

2002 ◽  
Author(s):  
S. F. Rogers ◽  
C. J. Evans
Keyword(s):  
United Kingdom ◽  
Fractured Rocks ◽  
Dependent Flow ◽  
Stress Dependent

Physical Modelling of Stress-dependent Permeability in Fractured Rocks

2012 ◽  
Vol 46 (1) ◽  
pp. 67-81 ◽  
Author(s):  
Lifang Zou ◽  
Boris G. Tarasov ◽  
Arcady V. Dyskin ◽  
Deepak P. Adhikary ◽  
Elena Pasternak ◽  
...  
Keyword(s):  
Fractured Rocks ◽  
Physical Modelling ◽  
Stress Dependent

Stress-dependent flow through fractured clay till: a laboratory study

1996 ◽  
Vol 33 (3) ◽  
pp. 449-457 ◽  
Author(s):  
John E Sims ◽  
Derek Elsworth ◽  
John A Cherry
Keyword(s):  
Fluid Migration ◽  
Fracture Permeability ◽  
Strongly Nonlinear ◽  
Clay Matrix ◽  
Flexible Wall ◽  
Flow Through ◽  
Compactive Effort ◽  
Dependent Flow ◽  
Stress Dependent ◽  
Stress Dependency

Stress-dependent hydraulic conductivities of weathered fractured clay till were measured in a flexible-wall permeameter. Measured conductivities were in the range 10–7 to 10–8 cm/s, of the same order as the clay matrix (10–8 cm/s), and representing equivalent hydraulic apertures in the range 0–5 μm. In general, the isolated fractures exhibited strongly nonlinear closure characteristics and hysteric behaviour under stress reversal. Some fracture samples exhibited only weak stress dependency, representing observable features of only nominal conductivity. Results of the investigations suggest fractures are closed to residuel aperture for an overburden load of the order of 12 m, this defining an effective closure depth and the degree of maximum useful compactive effort that might be applied to "seal" fractures and reduce fluid migration. Key words: fracture permeability, till, stress permeability, landfills.

scholarly journals STRESS SENSITIVITY ANALYSIS OF FRACTAL POROUS MEDIA BASED ON THE ELASTO-PLASTIC THICK-WALLED CYLINDER MODEL

Fractals ◽  
2021 ◽  
Vol 29 (03) ◽  
pp. 2150162
Author(s):  
ZHAOQIN HUANG ◽  
XIN SU ◽  
YANCHAO LI ◽  
KAI ZHANG ◽  
JUN YAO
Keyword(s):  
Porous Media ◽  
Fractal Theory ◽  
Fractal Model ◽  
Stress Sensitivity ◽  
Proposed Model ◽  
Cylinder Model ◽  
Stress Cycles ◽  
Dependent Flow ◽  
Stress Dependent ◽  
Walled Cylinder

The stress-dependent flow and transport behaviors of porous media are ubiquitous in various scientific and engineering applications. It has been shown that the change of effective stress has important effects on the permeability and porosity of porous media. In this paper, a new stress sensitivity model for porous media is developed based on the fractal theory and the elasto-plastic thick-walled cylinder model. The proposed model is able to predict the elasto-plastic deformation of the fractal porous media under loading–unloading stress cycles, which plays a crucial role on the permanent variations of the permeability and porosity. It is found that the permeability of stress-sensitivity porous media is related to the capillary fractal dimension, capillary fractal tortuosity dimension, minimum and maximum capillary diameters, Young’s modulus and Poisson’s ratio of capillary. Each parameter has a clear physical meaning. The validity of the developed fractal model is verified by comparing the model predictions with the available experimental data.

An Efficient Computational Model for Simulating Stress-dependent Flow in Three-dimensional Discrete Fracture Networks

2019 ◽  
Vol 23 (3) ◽  
pp. 1384-1394 ◽  
Author(s):  
Soheil Mohajerani ◽  
Gang Wang ◽  
Duruo Huang ◽  
S. M. E. Jalali ◽  
S. R. Torabi ◽  
...  
Keyword(s):  
Computational Model ◽  
Three Dimensional ◽  
Fracture Networks ◽  
Discrete Fracture Networks ◽  
Discrete Fracture ◽  
Dependent Flow ◽  
Stress Dependent

scholarly journals Numerical simulation of fluid injection in faulted and fractured rocks based on a fully-coupled hydro-mechanical model

2021 ◽  
Author(s):  
Lei Qinghua ◽  
Chin-Fu Tsang
Keyword(s):  
Fractured Rocks ◽  
Network Connectivity ◽  
Fracture Network ◽  
Elastic Response ◽  
Fluid Injection ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Stress Dependent ◽  
Strong Control ◽  
Fully Coupled

<p>We present a fully-coupled hydro-mechanical simulation of fluid injection-induced activation of pre-existing discontinuities, propagation of new damages, development of seismic activities, and alteration of network connectivity in naturally faulted and fractured rocks, which are represented using the discrete fracture network approach. We use the finite element method to compute the multiphysical fields including stress, strain, damage, displacement, and pressure by solving governing and constitutive equations of coupled solid and fluid domains. Essential hydro-mechanical coupling mechanisms are honoured such as pore pressure-induced shear slip of natural discontinuities, poro-elastic response of rock matrix, and stress-dependent permeability/storativity of both fractures and rocks. We use the numerical model developed to investigate the hydro-mechanical behaviour of deeply buried fractured rocks and fault zones in response to high-pressure fluid injection, with a specific focus on the system either below or above the percolation threshold. We observe a strong control of fracture network connectivity on the damage emergence, seismicity occurrence and connectivity change in the rock mass subject to hydraulic stimulation. We highlight the strong poro-elastic effect that tends to drive heterogeneous connectivity evolution of fracture systems during fluid injection. The results of our research and insights obtained have important implications for injection-related geoengineering activities such as the development of enhanced geothermal systems and extraction of hydrocarbon resources.</p>

scholarly journals Influence of initial aperture field under varied in-situ stress conditions on incipient karst formation in carbonate rocks

2020 ◽  
Author(s):  
Xiaoguang Wang ◽  
Mohammed Aliouache ◽  
Qinghua Lei ◽  
Hervé Jourde
Keyword(s):  
Fractured Rocks ◽  
Reactive Transport ◽  
Flow Direction ◽  
Onset Time ◽  
Fracture Network ◽  
In Situ Stress ◽  
Stress Conditions ◽  
Natural Fracture ◽  
Stress Dependent

<p>We use numerical simulations to investigate the role of initial aperture heterogeneity under varied in-situ stress loadings in the early-time karstification in an anisotropic natural fracture network. We found that the importance of the stress-dependent initial aperture effect on karstification depends on the relative relationship between the flow direction and structural hierarchy/anisotropy of the fracture network. When the flow occurs in the direction of the dominant fracture set with more through-going discontinuities, karst conduits only develop locally along a few large fractures with a preferential orientation for frictional sliding under the differential stress due to enhanced transmissivity caused by the important shear-induced dilation. In contrast, when flow is in the direction transverse to the dominant fracture set, the far-field stress loading has a negligible impact on the emergent dissolution pattern while only somewhat impact on the onset time of breakthrough. In this case, the developed conduits are much more tortuous with numerous branches. In both cases, the presence of initial aperture variability enhances the stress effects and significantly changes the dissolution pattern and delays the breakthrough time. Our results demonstrate that the flow heterogeneity induced by geometrical complexities and in-situ stress conditions seems to play an essential role in the karstification processes in fractured rocks.</p><p>The proposed reactive transport model based on realistic fracture networks may be used to investigate the spatial relationship between tectonic structures and karst cavities. Our results demonstrate that the heterogeneity induced by geometrical complexities and in-situ stress conditions may play a decisive role in the karstification processes in fractured rocks. Thus, they must be properly considered in reactive transport simulations to make reliable designs for practical engineering applications.</p><p><strong>Keywords</strong>: discrete fracture network, karst, network topology, reactive flow, in-situ stress</p>

A comparison of the United Kingdom Clinical Aptitude Test (UK-CAT) with a traditional admission selection process

2009 ◽  
pp. 1-6 ◽  
Author(s):  
Nishan Fernando ◽  
Gordon Prescott ◽  
Jennifer Cleland ◽  
Kathryn Greaves ◽  
Hamish McKenzie
Keyword(s):  
United Kingdom ◽  
Selection Process ◽  
Aptitude Test ◽  
The United Kingdom
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