Evaluation of Unsaturated Zone Air Permeability Through Pneumatic Tests

The air pressure in the unsaturated subsurface changes dynamically as the barometric pressure varies with time. Depending on the material properties and boundary conditions, the intensity of the correlation between the atmospheric and subsurface pressures may be evidenced in two persistent patterns: (1) the amplitude attenuation; and (2) the phase lag for the principal modes, such as the diurnal, semidiurnal, and 8-h tides. The amplitude attenuation and the phase lag generally depend on properties that can be classified into two categories: (1) The barometric pressure parameters, such as the apparent pressure amplitudes and frequencies controlled by the atmospheric tides and others; and (2) the material properties of porous media, such as the air viscosity, air-filled porosity, and permeability. Based on the principle of superposition and a Fourier time-series analysis, an analytical solution for predicting the subsurface air pressure variation caused by the atmospheric pressure fluctuation is presented. The air permeability (or pneumatic diffusivity) can be quantitatively determined by using the calculated amplitude attenuations (or phase lags) and the appropriate analytical relations among the parameters of the atmosphere and the porous medium. An analysis using the field data shows that the Fourier time-series analysis may provide a potentially reliable and simplemore » method for predicting the subsurface barometric pressure variation and for determining the air permeability of unsaturated zones.« less

Spatiotemporal variation in air density and associated effects on the wind-induced response of high-rise buildings

This document summarizes air permeability estimates obtained from single hole pneumatic injection tests in unsaturated fractured tuffs at the Covered Borehole Site (CBS) within the larger apache Leap Research Site (ALRS). Only permeability estimates obtained from a steady state interpretation of relatively stable pressure and flow rate data are included. Tests were conducted in five boreholes inclined at 45{degree} to the horizontal, and one vertical borehole. Over 180 borehole segments were tested by setting the packers 1 m apart. Additional tests were conducted in segments of lengths 0.5, 2.0, and 3.0 m in one borehole, and 2.0 m in another borehole, bringing the total number of tests to over 270. Tests were conducted by maintaining a constant injection rate until air pressure became relatively stable and remained so for some time. The injection rate was then incremented by a constant value and the procedure repeated. The air injection rate, pressure, temperature, and relative humidity were recorded. For each relatively stable period of injection rate and pressure, air permeability was estimated by treating the rock around each test interval as a uniform, isotropic porous medium within which air flows as a single phase under steady state, in a pressure field exhibiting prolate spheroidal symmetry. For each permeability estimate the authors list the corresponding injection rate, pressure, temperature and relative humidity. They also present selected graphs which show how the latter quantities vary with time; logarithmic plots of pressure versus time which demonstrate the importance of borehole storage effects during the early transient portion of each incremental test period; and semilogarithmic plots of pressure versus recovery time at the end of each test sequence.

A conceptual model was established to study the patterns of flow in vadose and saturated zones system induced by a prescribed boundary. Richards’ equation was adopted to describe groundwater flow in the vadose zone. Laplace transform and cosine Fourier transform were chosen to derive a semi-analytical solution of the governing equations. A finite-element numerical solution built with COMSOL software was used to test the semi-analytical solution. The buildups of the hydraulic head were investigated for different hydraulic parameters. Some noteworthy conclusions were obtained. The vadose zone parameters (constitutive exponent (κD) and specific yield (Sy)) have a significant effect on the buildups in the vadose zone and saturated zone. A larger κD value and smaller Sy value both lead to higher buildups in the vadose zone, while a larger κD value and a larger Sy value resulted in smaller buildups. As for the specific storage (Ss) of the saturated zone, the influence on buildup is more obvious in the saturated zone rather than in the vadose zone. The analysis further indicates that Media Anisotropy (Kz/Kx) value exhibits opposite influences on the hydraulic head in vadose and saturated zone. The present solution offers a valuable basis for further research of groundwater recharge and better design of MAR engineering.

To clarify differences in air permeability of the hose cloth of different types of pantyhose on the market in Japan, cylindrical model experiments and wearing experiments were conducted. The former was made to determine fundamental performance of the air permeability, and the latter, to evaluate the practical performance of worn pantyhose. Zokki, kohhen, sheer, wooly, and conjugate types of pantyhose were used as samples. There were large differences in air permeability among these fabrics when elongation was low or moderate. In around the maximum elongation state, almost the same high air permeability was shown regardless of pantyhose types. There were some pantyhose with lower air permeability while being worn, or other ones which have higher air permeability, regardless of posture, body shape, and sites of legs.

Abstract. The Somme River Basin is located above a chalk aquifer and the discharge of the somme River is highly influenced by groundwater inflow (90% of river discharge is baseflow). In 2001, the Somme River Basin suffered from a major flood causing damages estimated to 100 million euro (Deneux and Martin, 2001). The purpose of the present research is to evaluate the ability of four hydrologic models to reproduce flood events in the Somme River Basin over an 18-year period, by comparison with observed river discharge and piezometric level as well as satellite-derived extents of flooded area. The models used differ in their computation of surface water budget and in their representation of saturated and unsaturated zones. One model needed structural modification to be able to accurately simulate the riverflows of the Somme river. The models obtained fair to good simulations of the observed piezometric levels, but they all overestimate the piezometric level after flooding, possibly because of a simplistic representation of deep unsaturated flow. Models differ in their annual partition of the infiltration of water within the root zone (mostly driven by simulated evapotranspiration), but these differences are attenuated by water transfers within the saturated and unsaturated zone. As a consequence, the inter-model dispersion of the computed annual baseflow is reduced. The aquifer overflow areas simulated during flooding compare well with local data and satellite images. The models showed that this overflow occurs almost every year in the same areas (in floodplain), and that the flooding of 2001 was characterized by an increase in the quantity of the overflow and not much by a spreading of the overflow areas. Inconsistencies between river discharge and piezometric levels suggest that further investigation are needed to estimate the relative influence of unsaturated and saturated zones on the hydrodynamics of the Somme River Basin.

In this study more effective methods of applying a fluorochemical finish to relatively inexpensive melt blown/spunbond (MB/SB) nonwoven laminates developed in the Textiles and Nonwovens Development Center (TANDEC) at The University of Tennessee, Knoxville (UTK) were investigated with respect to improved performance and lower cost. The two possible end-uses for the MB/SB laminates are operating room drapes and gowns and apparel for agricultural workers, such as, pesticide applicators. In addition to comparing finishing techniques, the thermal bonding sequence of a MB/SB laminate before and after finishing also was studied to determine the effects on repellency, barrier properties, laminate bonding strength, air permeability and hand. Polypropylene melt blown webs produced on the 20-inch (0.51 m) Exxon melt blown pilot line at UTK were laminated with an experimental point bonded spunbond polypropylene fabric. Polypropylene melt blown and spunbond laminate samples were thermally bonded with a smooth roll calender both before and after fluorochemical (FC) finishing by the more conventional padding technique and by two low wet pickup methods, foam finishing and kiss roll applications. Repellency (oil, alcohol and water repellency), barrier properties (water impact resistance and air permeability), and bonding strengths were examined. Surprisingly, the MB/SB laminates, which were thermally bonded prior to finishing, picked up substantially less finish due to decreased porosity, but had much improved oil and alcohol repellency. The foam finished laminates had the highest oil and alcohol repellency values followed by those prepared by kiss roll and finally the padding techniques. Although all of the finished MB/SB laminates had excellent water spray ratings and water impact penetration resistance (due to the barrier properties of the melt blown component), the key to oil and alcohol repellency appears to be the concentration of FC finish deposited on the outer surface of the laminate. As would be expected, the thermally bonded laminates had lower air permeability, as compared to the unbonded laminates. The melt blown and the spunbond components separately had appreciably higher air permeability. However, the air permeability values of the MB/SB laminates, which were thermally bonded before FC finishing were generally greater than a slightly lower weight commercial spunbond/melt blown/spunbond (SMS) fabric, which had been thermally point bonded. Laminate bonding strengths were much lower than the commercial point bonded SMS fabric, but were believed to be suitable for some protective clothing applications.

Variations in air density from January 1972 to April 1975 at heights near 200 km

Great durability problems are being found in concrete structures related to the penetrability of aggressive agents through the concrete (ie. chloride penetration, sulphate attack, carbonation, freezing and thawing, and so on). Air permeability coefficient is used as an effective tool to estimate the potential durability of concrete structures due to its direct relation with the microstructure and the moisture content. This paper discusses the effect of the aggregate grading and water/cement ratio on the air permeability coefficient. An aggregate grading with more sand than coarse aggregates has resulted more beneficial from the point of view of concrete air permeability. This fact can be attributed to a denser skeleton formed by the finer aggregates. With fine aggregates, the higher water/cement ratio, the lower air permeability. However, the contrary was found with coarse aggregates. Overall, a temperature increase from 20 °C to 60 °C during preconditioning led to a Dair increase of 40–80%.

A series of soil column tests was performed to determine surfactant effects on residual water and oil saturations in porous media. In particular, these tests focused on the impact of submicellar surfactant solutions and the potential application of these low concentration systems to light nonaqueous phase liquid (LNAPL) contamination in the vadose zone. One set of tests involved surfactant flushing in soil‐filled columns followed by drainage to residual water saturation and LNAPL injection to determine the subsequent residual LNAPL saturation. Another set of tests involved surfactant application to a soil‐filled column already holding residual LNAPL saturation to promote the release of the previously trapped LNAPL. Test results showed surfactant systems could reduce both residual water and oil saturations by up to 50%. In addition, submicellar surfactant systems were equally effective as supramicellar solutions in reducing residual water saturations and potentially more effective at reducing residual oil saturations. Submicellar surfactant applications to a medium‐grained (0.85–0.425 mm) soil containing residual LNAPL saturations were effective at releasing up to 50% of the previously trapped residual LNAPL. These applications were less successful in a fine‐grained soil as full drainage of water and LNAPL was unachievable due to high capillary pressures. Overall, observations suggest low concentration surfactant solutions may have the ability to release significant amounts of previously trapped LNAPL in the vadose zone, potentially increasing free‐product recovery rates and lowering LNAPL saturations to levels more favorable for biodegradation. The decrease in overall saturations (both water and oil) in a contaminated vadose zone could also present an increase in air permeability, thus enhancing other vadose zone treatment technologies such as bioventing or soil vapor extraction.

TOSPAC is a computer program that calculates partially saturated groundwater flow with the transport of water-soluble contaminants. TOSPAC Version 1 is restricted to calculations involving one-dimensional, vertical columns of one or more media. TOSPAC was developed to help answer questions surrounding the burial of toxic wastes in arid regions. Burial of wastes in arid regions is attractive because of generally low population densities and little groundwater flow, in the unsaturated zone, to disturb the waste. TOSPAC helps to quantify groundwater flow and the spread of contamination, offering an idea of what could happen in the distant future. Figure 1.1 illustrates the problem TOSPAC was designed to investigate. For groundwater flow, TOSPAC can provide saturations, velocities, and and travel tunes for water in the rock matrix or the fractures in the unsaturated zone. TOSPAC can determine how hydrologic conditions vary when the rate of infiltration changes. For contaminant transport, TOSPAC can compute how much of a contaminant is dissolved in the water and how it is distributed. TOSPAC can determine how fast the solute is moving and the shape of the concentration front. And TOSPAC can be used to investigate how much of the contaminant remains in the inventory of a repository, how much is adsorbed onto the soil or rock matrix, and how much reaches the water table. Effective use of TOSPAC requires knowledge in a number of diverse disciplines, including real groundwater flow and transport, the mathematical models of groundwater flow and transport, real-world data required for the models, and the numerical solution of differential equations. Equally important is a realization of the limitations intrinsic to a computer model of complex physical phenomena. This User`s Guide not only describes the mechanics of executing TOSPAC on a computer, but also examines these other topics.

Multilayer three-dimensional (3D) fabrics are gaining importance due to their unique properties, which are significantly influenced by the interlocking pattern and govern their end-use applications, particularly in protective textiles requiring higher through-the-thickness mechanical characteristics. This research focuses on developing 3D woven structures with novel orthogonal through-the-thickness interlocking patterns: warp interlocked (WP-IL), weft interlocked (WT-IL), and hybrid interlocked (HB-IL) by using warp and weft yarns simultaneously for interlocking fabric layers. Various performance characteristics, including air permeability, thermal conductivity, compression resistance, bending rigidity, tensile strength, and puncture resistance, were evaluated to assess the influence of fabric structure. Statistical analysis using One-way ANOVA was conducted to determine the significance of the interlocking pattern on these properties. The results indicate that weft interlock structures exhibit the highest air permeability due to their greater porosity, whereas hybrid interlock and warp interlock structures show 20.7% and 18% lower air permeability, respectively, due to their reduced structural porosity. Thermal conductivity results suggest no significant differences in insulation properties among the structures. Hybrid interlock fabrics demonstrate superior compression resistance and tensile strength, with 26.2% higher tensile strength than warp interlock structures and 12.3% higher than weft interlock structures in the warp direction, owing to the balanced distribution of binding yarns. In contrast, warp interlock structures exhibit the lowest bending rigidity in the weft direction, making them more flexible. Additionally, hybrid interlock structures provide the highest puncture resistance, while weft interlock structures show the lowest resistance due to their increased porosity. These findings highlight the critical role of fabric architecture in determining both comfort and mechanical properties, providing valuable insights for selecting optimal 3D woven structures in applications requiring specific performance attributes.

Air density at heights near 190 km in 1966–67, from the orbit of Secor 6

In paper 1 of this two‐part series we described a three‐dimensional numerical inverse model for the interpretation of cross‐hole pneumatic tests in unsaturated fractured tuffs at the Apache Leap Research Site (ALRS) near Superior, Arizona. Our model is designed to analyze these data in two ways: (1) by considering pressure records from individual borehole monitoring intervals one at a time, while treating the rock as being spatially uniform, and (2) by considering pressure records from multiple tests and borehole monitoring intervals simultaneously, while treating the rock as being randomly heterogeneous. The first approach yields a series of equivalent air permeabilities and air‐ filled porosities for rock volumes having length scales ranging from meters to tens of meters, represented nominally by radius vectors extending from injection to monitoring intervals. The second approach yields a high‐resolution geostatistical estimate of how air permeability and air‐filled porosity, defined on grid blocks having a length scale of 1 m, vary spatially throughout the tested rock volume. It amounts to three‐dimensional pneumatic “tomography” or stochastic imaging of the rock. Paper 1 described the field data, the model, and the effect of boreholes on pressure propagation through the rock. This second paper implements our inverse model on pressure data from five cross‐hole tests at ALRS. We compare our cross‐hole test interpretations by means of the two approaches with earlier interpretations by means of type curves and with geostatistical interpretations of single‐hole test data. The comparisons show internal consistency between all pneumatic test interpretations and reveal a very pronounced scale effect in permeability and porosity at ALRS.

Proposed models and analytical solutions of steady one‐ and three‐dimensional (3D) air flow in partially saturated soil enable estimating air‐injection sources in unsaturated soils and optimizing their application. The 3D modeling offers six solutions for air injection from a point source located in a: (i) laterally unconfined domain and (ii) at the center of a cylindrically confined domain, in (a) an infinite, vertically unconfined domain, (b) a vertically semi‐infinite domain with a surface of constant pressure above the source, representing the effect of the atmosphere on air flow, and (c) with an impermeable surface below the source, representing the effect of a water table on the air flow. The 3D models were formulated using known mathematical solutions for water flow and adjusting them to describe air flow, assuming full analogy between the effect of gravitation on water flow to the effect of buoyancy on air flow. One‐dimensional air injection simulations based on two types of air‐permeability functions (a concaved exponential and a convex exponential) result in similar distributions of air pressure and capillary heads. Thus, the error caused by using the convex (of positive curvature) exponential function for linearizing the flow equation and for obtaining the 3D solutions is bounded, which justifies use of this function. Air flow patterns depend on a single soil characteristic parameter (α), indicative of the ratio between effects of buoyancy and capillary forces driving the air; high values indicate more upwardly oriented flow. The proposed analysis can be used for decision making regarding locations and depths of air‐injection sources for aeration in the vadose zone. Based on the air pressure distribution and the streamlines outlined by the relevant solutions we conclude that the effect of the water table below the source on air flow is negligible, especially in cylindrical confinements. Furthermore, the effect of the atmosphere on air flow in a cylindrical domain is also negligible. The proposed models are applicable especially when the air‐pressure gradient in the soil is relatively small, and the effect of air compressibility is negligible.