Permeability (earth sciences)

About: Permeability (earth sciences) is a research topic. Over the lifetime, 15424 publications have been published within this topic receiving 288535 citations.

A Method of Determining the Permeability and Effective Porosity of Unconfined Anisotropie Aquifers

Abstract: The equations of unsteady flow toward a partially penetrating well in an unconfined aquifer of finite thickness are solved by linearization. It is assumed that the aquifer is nondeformable and that the effective porosity at the water table is constant. It is also assumed that the aquifer is anisotropic (the principal axes of the permeability tensor being horizontal and vertical, respectively), that the pumping discharge is constant, and that the drawdowns are small. The vertical component of the flow velocity is not neglected. The solution is, therefore, equally valid in the vicinity and at large distances from the pumping well. In the latter case, it coincides with the Theis solution. A method of matching the theoretical solution with drawdown measurements during pumping tests is outlined. By the matching method the horizontal and vertical hydraulic conductivities and the effective porosity of the aquifer may be determined. The method is illustrated by analyzing data from pumping tests carried out in three anisotropic aquifers.

Darcy's law in saturated kaolinite

Abstract: Data obtained with a new laboratory technique for measuring the hydraulic conductivity of saturated clays show that Darcy's law is obeyed at low gradients in saturated kaolinite over a wide range of porosities. The new technique involves producing arbitrary constant flow rates through a rigidly confined clay sample, using a multispeed syringe pump, and measuring the gradients induced thereby with a differential pressure transducer. This procedure avoids the errors in the conventional technique that arise from atmospheric contamination and from the long time intervals needed to obtain measurable flow rates. The results presented, together with the previous evidence, suggest that Darcy's law is valid in many saturated natural clays and clayey sediments, but that exceptions may occur in extremely fine-grained clays and also where high gradients are present in shallow, unconfined sediments or in granular soils containing small amounts of clay. (Key words: Permeability; porous mediums.)

Evolution of dilatancy and permeability in rock salt during hydrostatic compaction and triaxial deformation

Abstract: Combined gas permeability and P and S wave velocity measurements were carried out on rock salt samples from the Gorleben salt dome and the Morsleben salt mine under hydrostatic and triaxial loading condions, mostly at room temperature. Permeabilities in the as-received samples vary between 10(-16) and 2x10(-20) m(2). The initial permeability is primarily due to decompaction induced by drilling core retrieval and sample preparation. Hydrostatic loading gives rise to a marked decrease of permeability and a coeval significant increase of P and S wave velocities due to progressive closure of grain boundary cracks, tending to approach the in situ matrix permeability ( 18 MPa differential stress at 10 MPa confining pressure to similar to 30 MPa at confining pressures above similar to 70 MPa. Dilatancy is due to the opening of grain boundary and (100) cleavage cracks and depends on the applied confining pressure. The orientation of the open cracks is primarily controlled by the loading geometry system (compression, extension). As a consequence, permeability increases dramatically with progressive dilatancy, followed by a period of plus/minus constant permeability during strain hardening up to 10% axial strain or even more. This suggests that the evolution of permeability is not only a function of dilatancy but also of microcrack linkage. Importantly, the anisotropic crack array within the samples causes a strong directional dependence of permeability.

Permeability measurement of textile reinforcements with several test fluids

Abstract: In liquid composite moulding (LCM) techniques, the liquid resin has to flow a long distance to impregnate the dry fibres. The measure for the resistance of the fibre preform to the resin flow is the permeability of the fibre preform. Because of the dual-scale porous structure of the textile preforms, test fluid can influence the unsaturated permeability values through the interaction of the fluid and fibres. In this study, the influence of test fluid on the permeability measurement of several types of textile reinforcements is investigated. First the contact angle of various fluids and fibres was measured. Then the permeability measurement of the textile reinforcements was carried out. The results showed that the influence of test fluid is small under the test conditions.