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.

A Coupled Overlapping Domain Method for the Computation of Transitional Flow Through Artificial Heart Valves

2012 ◽  
Author(s):  
A. C. Verkaik ◽  
A. C. B. Bogaerds ◽  
F. Storti ◽  
F. N. van de Vosse
Keyword(s):  
High Speed ◽  
Heart Valves ◽  
Reynolds Numbers ◽  
Transitional Flow ◽  
Small Scale ◽  
High Deformation ◽  
Artificial Heart Valves ◽  
Laminar And Turbulent Flow ◽  
Flow Through ◽  
Dependent Flow

When blood is pumped through the aortic valves, it has a time dependent flow with a relatively high speed, resulting in Reynolds numbers between 1500 and 3000. Hence, flow is in the transitional regime between laminar and turbulent flow. Transitional flow contains small scale fluctuations, see Figure 1, and may result in local high deformation rates.

Microvascular dilation in response to occlusion: a coordinating role for conducted vasomotor responses

2000 ◽  
Vol 279 (1) ◽  
pp. H279-H284 ◽  
Author(s):  
Kim A. Dora ◽  
David N. Damon ◽  
Brian R. Duling
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Third Order ◽  
Vasomotor Responses ◽  
Vasodilatory Response ◽  
Flow Through ◽  
Stress Dependent ◽  
Dependent Mechanism

In rat cremasteric microcirculation, mechanical occlusion of one branch of an arteriolar bifurcation causes an increase in flow and vasodilation of the unoccluded daughter branch. This dilation has been attributed to the operation of a shear stress-dependent mechanism in the microcirculation. Instead of or in addition to this, we hypothesized that the dilation observed during occlusion is the result of a conducted signal originating distal to the occlusion. To test this hypothesis, we blocked the ascending spread of conducted vasomotor responses by damaging the smooth muscle and endothelial cells in a 200-μm segment of second- or third-order arterioles. We found that a conduction blockade eliminated or diminished the occlusion-associated increase in flow through the unoccluded branch and abolished or strongly attenuated the vasodilatory response in both vessels at the branch. We also noted that vasodilations induced by ACh (10−4 M, 0.6 s) spread to, but not beyond, the area of damage. Taken together, these data provide strong evidence that conducted vasomotor responses have an important role in coordinating blood flow in response to an arteriolar occlusion.

Monolayer Microproppant-Placement Quality Using Split-Core-Plug Permeability Measurements Under Stress

SPE Journal ◽  
2019 ◽  
Vol 24 (04) ◽  
pp. 1790-1808 ◽  
Author(s):  
Brice Y. Kim ◽  
I. Yucel Akkutlu ◽  
Vladimir Martysevich ◽  
Ronald G. Dusterhoft
Keyword(s):  
Pressure Pulse ◽  
Fracture Permeability ◽  
Permeability Model ◽  
Eagle Ford ◽  
Areal Distribution ◽  
Stimulation Experiments ◽  
Stress Dependent

Summary The stress-dependent permeabilities of split shale core plugs from Eagle Ford, Bakken, and Barnett Formation samples are investigated in the presence of microproppants. An analytical permeability model is developed for the investigation, including the interactions between the fracture walls and monolayer microproppants under stress. The model is then used to analyze a series of pressure-pulse-decay measurements of the propped shale samples in the laboratory. The analysis provides the propped-fracture permeability of the samples and predicts a parameter related to the quality of the proppant areal distribution in the fracture. The proppant-placement quality can be used as a measure of success of the delivery of proppants into microfractures and to design stimulation experiments in the laboratory.

scholarly journals Experimental Study on Stress-Dependent Nonlinear Flow Behavior and Normalized Transmissivity of Real Rock Fracture Networks

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Qian Yin ◽  
Hongwen Jing ◽  
Richeng Liu ◽  
Guowei Ma ◽  
Liyuan Yu ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Rock Fracture ◽  
Hydraulic Gradient ◽  
Nonlinear Flow ◽  
Fracture Networks ◽  
Critical Hydraulic Gradient ◽  
Boundary Load ◽  
Flow Through ◽  
Stress Dependent ◽  
Rock Fracture Networks

The mechanism and quantitative descriptions of nonlinear fluid flow through rock fractures are difficult issues of high concern in underground engineering fields. In order to study the effects of fracture geometry and loading conditions on nonlinear flow properties and normalized transmissivity through fracture networks, stress-dependent fluid flow tests were conducted on real rock fracture networks with different number of intersections (1, 4, 7, and 12) and subjected to various applied boundary loads (7, 14, 21, 28, and 35 kN). For all cases, the inlet hydraulic pressures ranged from 0 to 0.6 MPa. The test results show that Forchheimer’s law provides an excellent description of the nonlinear fluid flow in fracture networks. The linear coefficient a and nonlinear coefficient b in Forchheimer’s law J=aQ+bQ2 generally decrease with the number of intersections but increase with the boundary load. The relationships between a and b can be well fitted with a power function. A nonlinear effect factor E=bQ2/(aQ+bQ2) was used to quantitatively characterize the nonlinear behaviors of fluid flow through fracture networks. By defining a critical value of E = 10%, the critical hydraulic gradient was calculated. The critical hydraulic gradient decreases with the number of intersections due to richer flowing paths but increases with the boundary load due to fracture closure. The transmissivity of fracture networks decreases with the hydraulic gradient, and the variation process can be estimated using an exponential function. A mathematical expression T/T0=1-exp⁡(-αJ-0.45) for decreased normalized transmissivity T/T0 against the hydraulic gradient J was established. When the hydraulic gradient is small, T/T0 holds a constant value of 1.0. With increasing hydraulic gradient, the reduction rate of T/T0 first increases and then decreases. The equivalent permeability of fracture networks decreases with the applied boundary load, and permeability changes at low load levels are more sensitive.

scholarly journals Effective Continuum Approximations for Permeability in Brown-Coal and Other Large-Scale Fractured Media

Geosciences ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 511
Author(s):  
Roger Hu ◽  
Stuart D. C. Walsh
Keyword(s):  
Brown Coal ◽  
Large Scale ◽  
Fracture Network ◽  
Open Pit ◽  
Fracture Permeability ◽  
Permeability Model ◽  
Wide Range ◽  
Fracture Apertures ◽  
Stress Dependent ◽  
Fracture Distribution

The stability of open-pit brown-coal mines is affected by the manner in which water is transmitted or retained within their slopes. This in turn is a function of the in-situ fracture network at those mines. Fracture networks in real mines exhibit significant degrees of heterogeneity; encompassing a wide range of apertures, inter-fracture separations, and orientations. While each of these factors plays a role in determining fluid movement, over the scale of a mine it is often impractical to precisely measure, let alone simulate, the behaviour of each fracture. Accordingly, effective continuum models capable of representing the bulk effects of the fracture network are needed to understand the movement of fluid within these slopes. This article presents an analysis of the fracture distribution within the slopes of a brown coal mine and outlines a model to capture the effects on the bulk permeability. A stress-dependent effective-fracture-permeability model is introduced that captures the effects of the fracture apertures, spacing, and orientation. We discuss how this model captures the fracture heterogeneity and the effects of changing stress conditions on fluid flow. The fracture network data and the results from the effective permeability model demonstrate that in many cases slope permeability is dominated by highly permeable but low-probability fractures. These results highlight the need for models capable of capturing the effects of heterogeneity and uncertainty on the slope behaviour.

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