Permeability and stress

The equivalent permeability tensor K j has been computed at 2 m scale considering the real length of the joint (we have shown the importance to avoid artificial joint prolongations). The REV could not be estimated due to code limitation reasons. The relation between permeability and stress (considering an isotropic state of stress) has been determined and is highly dependent on the joint stiffness value. 

According to studies abroad and at home, with mechanical stress the permeability decreases rapidly. But when stress is stronger, the decrease can be very limited and remains basically stable (Sheng 2007). The relationship between the permeability and stress is available to be presented by the following formula in the stress range from 0-4 MPa to 15-40 MPa ... 

Gaillard, P.J., de Boer, A.G., Breimer, D.D., 1996. BloodM rain barrier permeability and stress a study on excitotoxic stress and vasogenic edema. Eur. J. Pharm. Sci. 4, S195. 

The eddy current method allows to evalute the state of stress in ferromagnetic material. The given method is used for determining own stress as well as that formed in effect of outside load. With regard to physical principles of own stress analysis, the dependence between the magnetic permeability and the distance between atomic surfaces is utilized. 

PP bead foams of a range of densities were compressed using impact and creep loading in an Instron test machine. The stress-strain curves were analysed to determine the effective cell gas pressure as a function of time under load. Creep was controlled by the polymer linear viscoelastic response if the applied stress was low but, at stresses above the foam yield stress, the creep was more rapid until compressed cell gas took the majority of the load. Air was lost from the cells by diffusion through the cell faces, this creep mechanism being more rapid than in extruded foams, because of the small bead size and the open channels at the bead bonndaries. The foam permeability to air conld be related to the PP permeability and the foam density. 15 refs. 

The PF technology also has several potential limitations. Fractures do not always propagate in the direction or to the distances expected. Fractures may open new pathways for the unwanted spread of contaminants. Pockets of low permeability may remain after fracturing. Surface heave and stress resulting from the process can create hazards for buildings or other structures at a site. If the moisture content of the contaminated media is not controlled, the formation may swell and close the fractures. PF is not applicable at sites with high natural permeabilities. Fractures will close in soils with low clay content. In addition, PF should not be used in areas of high seismic activity. 

Sowokinos, J. R., Orr, P. H., Knoper, J. A., Yarns, J. L. (1987). Influence of potato storage and handling stress, sugars, chip quality and integrity of the starch (amyloplast) membrane. Am. Potato J., 64,213-225. Spychalla,N. R, Desborough, S. L. (1990). Fatty acids, membrane permeability, and sugars of stored potato tubers. Plant Physiol., 94, 1207-1213. 

P.M. Biesheuvel and H. Verweij, Ceramic Membrane Supports, Permeability, Tensile Strength and Stress , J. Membrane Sci. 156 141-52 (1999). 

There are many hazards involved in such operations untoward chemical reactions can arise between fluid and solid phases, leading to permeability impairment stresses may exceed the mechanical strength of the reservoir matrix vertical flows may arise because of fluid density differences that lead to rapid breakthrough of unwanted fluid. 

The gradient dependence of viscosity of flexible coils is a much more complicated problem than that of rigid particles. In addition to orientation under shearing stress the permeable and deformable nature of these molecules leads to such theoretical and conceptual difficulties that no adequate theory has as yet been found to be of general applicability. Kirkwood and... 

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