The Microstructural Response of Articular Cartilage at Peak Internal Pore Pressure: A Comparison Between Normal and Degenerate Matrices

2008 ◽  
Author(s):  
James M. Fick ◽  
Ashvin Thambyah ◽  
Neil D. Broom
Keyword(s):  
Articular Cartilage ◽  
Pore Pressure ◽  
Direct Compression ◽  
Pore Pressures ◽  
The Relationship ◽  
Internal Pore

This study was aimed at investigating the relationship between the microstructural responses of healthy (normal) versus mildly osteoarthritic articular cartilage and their associated peak internal pore pressures, when subjected to direct compression.

The Influence of Internal Pore Pressure During Roll Forming of Structurally Porous Metals

1998 ◽  
Vol 521 ◽  
Author(s):  
D. M. Elzey ◽  
H. N. G. Wadley
Keyword(s):  
Pore Pressure ◽  
High Pressures ◽  
Hot Isostatic Pressing ◽  
Matrix Material ◽  
Porous Metal ◽  
Roll Forming ◽  
Dense Matrix ◽  
Porous Metals ◽  
Noticeable Effect ◽  
Internal Pore

ABSTRACTStructurally porous metal sandwich panels consisting of dense face sheets and porous cores of controlled relative density can be manufactured by trapping inert gas during hot isostatic pressing and modifying its distribution via subsequent thermo-mechanical forming. At high pressures, the internal gas is expected to influence the forming response. This paper describes a model for the roll forming of a porous metal panel and its use to explore the effects of internal pore pressure upon rolling response. It is shown that for gas pressures below about half the yield strength of the fully dense matrix material, there is essentially no influence on the forming response. Only in the case of very high initial pore pressures or at relative densities approaching full theoretical does a noticeable effect arise. In this case, a limiting upper density is attainable which depends on the specific rolling conditions and geometry.

Deformation of Chalk Under Confining Pressure and Pore Pressure

1981 ◽  
Vol 21 (01) ◽  
pp. 43-50 ◽  
Author(s):  
Thomas Lindsay Blanton
Keyword(s):  
Mechanical Behavior ◽  
Pore Pressure ◽  
Hydrostatic Stress ◽  
Confining Pressure ◽  
Low Permeability ◽  
High Porosity ◽  
Pore Collapse ◽  
Soft Matrix ◽  
Pore Pressures ◽  
Ductile Behavior

Abstract Compression tests with and without pore pressure have been run on Danian and Austin chalks. The rocks yielded under increasing hydrostatic stress by pore collapse. The same effect was produced by holding a constant hydrostatic stress and reducing the pore pressure. This pore collapse reduced the permeability. The ultimate strength of the chalks increased with increasing confining pressure. The yield strength increased initially, but at higher confining pressures it decreased until it yielded under hydrostatic stress. Relatively high pore-pressure gradients developed when the chalks. were compressed. In these situations, the mechanical behavior tended to be a function of the average effective stresses. Introduction Hydrocarbons have been found in chalks in the North Sea, the Middle East, the Gulf Coast and midcontinent regions of the U.S., and the Scotian Shelf of Canada1; however, problems have been encountered in developing these reservoirs efficiently because of the unusual mechanical behavior of chalk. Chalks have three characteristics that interact to differentiate their behavior from most reservoir rocks. High Porosity. Porosities may be as high as 80070.1,2 Effects of burial and pore-water chemistry can reduce this porosity to less than 1%, but notable exceptions occur in areas of early oil placement and overpressuring where porosities in excess of 40% have been reported.2,3 Low Permeability Regardless of porosity, chalks have low permeabilities, usually around 1 to 10 md. Soft Matrix. Chalks are predominantly calcite, which has a hardness of 3 on Mohr's scale. These properties create problems in the following areas of reservoir development. Drilling. High porosity combined with a soft matrix material makes for a relatively weak and ductile rock. Efficient drilling involves chipping the rock and ductile behavior inhibits this process. Stimulation. The combination of high porosity and low permeability makes chalks prime candidates for stimulation by hydraulic fracturing or acid fracturing. The best production often is associated with natural fractures.2,3 Man-made fractures could open up new areas to production, but again ductile behavior inhibits the fracturing process. Production. In many cases permeabilities are low enough to trap pore fluids and cause abnormally high pore pressures.2 These high pore pressures help maintain the high porosities at depth by supporting some of the weight of the overburden. As the field is produced and the pore pressure lowered, some of the weight will shift to the soft matrix. The result may be pore collapse and reduction of an already low permeability. These problems indicate a need for basic information on the mechanical behavior of chalks. Determining methods of enhancing brittle behavior could lead to improved drilling and stimulation techniques. The ability to predict and prevent pore collapse could increase ultimate recovery. The approach taken in this study was experimental. Specimens of chalk were subjected to different combinations of stress and pore pressure in the laboratory, and the resulting deformations were measured.

Dissipation Pattern of Excess Pore Pressure After Liquefaction in Saturated Sand Deposits

2003 ◽  
Vol 1821 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Ik Soo Ha ◽  
Young Ho Park ◽  
Myoung Mo Kim
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Dynamic Loading ◽  
Time History ◽  
Excess Pore Pressure ◽  
Pore Pressures ◽  
Dissipation Pattern ◽  
Effective Grain Size ◽  
Coefficient Of Uniformity ◽  
Excess Pore

In liquefied areas, the amount of damage to a structure is mainly affected by the postliquefaction behavior of the liquefied ground. Understanding postliquefaction behavior requires understanding the dissipation pattern of excess pore pressure after liquefaction. It is difficult to measure pore pressures generated and dissipated during an earthquake because of the more-or-less randomness of earthquake events. Researchers have artificially generated liquefaction with sand samples in the laboratory and have simulated curves for the time history dissipation of excess pore pressure. To estimate variation in permeability during dynamic loading, which should be known for settlement predictions of the ground undergoing liquefaction, 1-g shaking table tests were carried out on five kinds of sands, all with high liquefaction potentials. During tests, excess pore pressures at various depths and surface settlements were measured. The measured curve of the excess pore pressure dissipation was simulated using the solidification theory. From analysis of the velocity of dissipation, the dissipation pattern of excess pore pressure after liquefaction was examined. Permeability during dissipation was calculated using the measured settlement and dissipation velocity, also used for estimating permeability during dynamic loading. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The increase in the ground’s initial relative density played a role in shifting this correlation curve toward increased dissipation velocity. Permeability during liquefaction increased 1.4 to 5 times compared with the permeability of the original ground, the increase becoming greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

scholarly journals The relationship between treadmill running and HIF-2α on rat knee articular cartilage

2018 ◽  
Vol 26 ◽  
pp. S399
Author(s):  
S. Shimomura ◽  
H. Inoue ◽  
Y. Arai ◽  
S. Nakagawa ◽  
S. Tsuchida ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Treadmill Running ◽  
The Relationship

Study about Characteristics of Cement Paste on Fractal Theory

2013 ◽  
Vol 423-426 ◽  
pp. 1051-1054
Author(s):  
Tian Yang Zhai
Keyword(s):  
Compressive Strength ◽  
Fractal Dimension ◽  
Cement Paste ◽  
Permeability Coefficient ◽  
Fractal Theory ◽  
Fractal Model ◽  
Concrete Compressive Strength ◽  
Internal Pore Structure ◽  
The Relationship ◽  
Internal Pore

A fractal model to simulate cement paste internal pore structure, and on this basis deduce that fractal dimension is D and the corresponding pore is r, the relationship between porosity is P. MIP was measured test. Then calculated the different ages of the fractal dimension of cement and concrete compressive strength, tensile strength and permeability coefficient. The results showed that: compressive strength, permeability and fractal dimension has a good correlation. Whey in cement in the process of hydration of cement products continue to fill the pores, making the compressive strength increased 70%, permeability is declining.

The effect of adsorption and Knudsen diffusion on the steady-state permeability of microporous rocks

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. D75-D83 ◽  
Author(s):  
Adam M. Allan ◽  
Gary Mavko
Keyword(s):  
Steady State ◽  
Pore Pressure ◽  
Effective Permeability ◽  
Knudsen Diffusion ◽  
Adsorbed Layer ◽  
Pore Fluid ◽  
Fluid Simulation ◽  
Apparent Permeability ◽  
Pore Pressures ◽  
The Continuum

Microporous rocks are being increasingly researched as novel exploration and development technologies facilitate production of the reserves confined in the low-permeability reservoir. The ability to numerically estimate effective permeability is pivotal to characterizing the production capability of microporous reservoirs. In this study, a novel methodology is presented for estimating the steady-state effective permeability from FIB-SEM volumes. We quantify the effect of a static adsorbed monolayer and Knudsen diffusion on effective permeability as a function of pore pressure to better model production of microporous rock volumes. The adsorbed layer is incorporated by generating an effective pore geometry with a pore pressure-dependent layer of immobile voxels at the fluid-solid interface. Due to the steady-state nature of this study, surface diffusion within the adsorbed layer and topological variations of the layer within pores are neglected, potentially resulting in underestimation of effective permeability over extended production time periods. Knudsen diffusion and gas slippage is incorporated through computation of an apparent permeability that accounts for the rarefaction of the pore fluid. We determine that at syn-production pore pressures, permeability varies significantly as a function of the phase of the pore fluid. Simulation of methane transport in micropores indicates that, in the supercritical regime, the effect of Knudsen diffusion relative to adsorption is significantly reduced resulting in effective permeability values up to 10 nanodarcies ([Formula: see text]) less or 40% lower than the continuum prediction. Contrastingly, at subcritical pore pressures, the effective permeability is significantly greater than the continuum prediction due to rarefaction of the gas and the onset of Knudsen diffusion. For example, at 1 MPa, the effective permeability of the kerogen body is five times the continuum prediction. This study demonstrates the importance of, and provides a novel methodology for, incorporating noncontinuum effects in the estimation of the transport properties of microporous rocks.

Hydraulic fracturing from induced pore pressures in clay soils

1983 ◽  
Vol 20 (3) ◽  
pp. 546-555
Author(s):  
H. B. Poorooshasb ◽  
Raymond N. Yong
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Clay Soil ◽  
Elastic Analysis ◽  
Load Step ◽  
Pressure Fields ◽  
Pore Pressures ◽  
Central Elements ◽  
Excess Pore Pressures ◽  
State Of Tension

The possibility of induced high excess pore pressures during consolidation of a clay soil with transverse drainage developing hydraulic fracturing in the soil is presented. The elastic analysis pursued herein examines the stress and pore pressure fields generated under vertical consolidation loading with drainage allowed only in the transverse direction. The results indicate that when the load step increments are too large, in comparison with previous loads, the transverse effective stress associated with the central elements of the soil being loaded can become negative. At that time, a state of tension will be created and a form of hydraulic fracturing will result. Key words: pore pressure, hydraulic fracture, elastic analysis, transverse drainage, consolidation.

scholarly journals The relationship between knee pain and MR relaxation in medial tibial articular cartilage

2013 ◽  
Vol 21 ◽  
pp. S194-S195
Author(s):  
J. Schooler ◽  
D. Kumar ◽  
X. Li ◽  
T. Link ◽  
S. Majumdar
Keyword(s):  
Articular Cartilage ◽  
Knee Pain ◽  
Mr Relaxation ◽  
The Relationship
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