Permeameters

Permeabilitat, /. permeability. Permeabilltatsmesser, m. permeameter. permisch, a. Geol.) Permian, permutieren, v.i. Math.) permute treat with permutite. 

Two types of instruments are employed to determine the specific surface area by permea-metry. Those of the first type are called constant pressure systems, and the Fisher subsieve sizer is a typical example that belongs to such systems. Instruments of the second type are known as constant volume permeameters, and the apparatus devised by Blain is an example. 

Aside from the difficulty in correlating soil radon measurements with indoor radon measurements, various field studies have also shown that obtaining a representative soil gas measurement is difficult. Soil gas radon measurements were made with a permeameter in seven central Florida houses.42... 

Darcy s work was confined to the quantity of water discharged from a sand filter. Four examples of the application of Darcy s law as applied through a sand filter (actually a permeameter) is shown in Figure 3.10. Notice that the orientation of the cylinder has no effect on permeability. An example calculation of hydraulic conductivity (K) is presented in Figure 3.10 using the equation below ... 

Determination of the actual velocity of the water through the permeameter used in Figure 3.13 is presented below ... 

FIGURE 3.13 Examples of the application of Darcy s law for the movement of water through a sand filter or permeameter. 

Darcy s law (Q = KIA) is the operating factor in well flow. The only significant difference in the application of this law to wells rather than to a laboratory per-meameter is that the water flows to the well from a radial pattern rather than via linear flow as shown in the permeameter. The flow paths found in both artesian and... 

Through-plane permeability is usually one of the most common parameters given by manufacturers for carbon fiber papers and carbon cloths, even though it is often not specified as through-plane permeability. It is important to note that commercial instruments, such as permeameters and Gurley method instruments, are used in the fuel cell industry to measure this permeability [197,218]. 

Alternatives to batch testing include the use of diffusion cells or flowthrough columns. Diffusion cells are easier to operate, but are less representative of field conditions where some advection may occur. However, operation of columns at very low flow rates is difficult and subject to artifacts. To minimize possible wall effects associated with shrink/swell behavior of low-permeability clay materials, several researchers have utilized column devices that provide a confining pressure, such as flexible wall permeameters (e.g., Acar and Haider, 1990 Smith and Jaffe, 1994 Shackelford and Redmond, 1995 Khandelwal et al., 1998 Khandelwal and Rabideau, 2000). 

The mean hydraulic conductivities for the aquifer sand determined using the two laboratory methods (constant-head and falling-head permeameters) were 5 10"4 m sec"1 and 2 1 O 4 m sec"1, respectively. The isotherm results showed that the sand had negligible sorption capacity for either chromate 01 PCE. 

Material Hydraulic Conductivity (m/sec 10 3) Constant-Head Permeameter Falling-Head Permeameter Slug Test... 

The full set of equations was used to model experiments from the literature using numerical methods. In one of these experiments [3], a clay sample in a flexible wall permeameter was subjected to a salt concentration gradient and salinity and pressure profiles were measured. In [4], a scripted finite element solver was used to provide numerical simulations. Using a least mean squares fit, the storage parameter and the reflection coefficient were inferred from the experimental data. Relevant parameters for this experiment are shown in Table 2. 

Abstract A permeameter was developed for measurement of coupled flow phenomena in clayey materials. Results are presented on streaming potentials in a Na-bentonite induced by hydraulic flow of electrolyte solutions. Transport coefficients are derived from the experiments, assuming the theory of irreversible thermodynamics to be applicable. Hydraulic and electro-osmotic conductivities are consistent with data reported elsewhere. However the electrical conductivity of the clay is substantially lower. This is ascribed to the high compaction of the clay resulting in overlap of double layers... 

The present study is aimed at assessing the magnitude of the counterflow of water in bentonite clay, using a permeameter without short-circuiting the clay. In the experiments presented here water flow is initiated by a hydraulic gradient. By using the theory of irreversible thermodynamics, the counterflow by induced electro-osmosis, quantified in this paper, will provide an indication of the effect of active application of electro-osmosis in the clay. 

The sample was placed in the permeameter and the cell was partly filled with silicone oil. Thereafter a pressure of 1 bar was applied by use of argon gas. Both reservoirs were filled with the same NaCl-solution used for sat-... 

Table 2. Water fluxes and driving forces derived from permeameter experiments with water of two different salt concentrations...

The dispersion phenomenon in the two humid soils (Pembroke and Uniontown) was evaluated through the use of an Imhoff cone test and a permeameter. The Imhoff cone is commonly used by engineers to determine settleable solids (see Chapter 9). The results of clay dispersion obtained by the Imhoff cone test are expressed as a dispersion index (percent of total clays in the soil sample dispersed), which is correlated with relative saturated hydraulic conductivity. This is shown in Figure 11.5. It demonstrates that each of the soils, depending on its clay content (Pembroke 59% Uniontown 20%), exhibits unique saturated hydraulic conductivity behavior with respect to the dispersion index. Also, in each of the soils, various mechanisms (different line slopes) appear to control saturated hydraulic conductivity. 

The air-void content of asphalt concrete mixes affects mix permeability and is therefore very important from a pavement durability standpoint. The permeability of various sulfur-extended binder mixes, prepared at a variety of air-void contents, was measured with an air permeameter similar to that described in Ref. 16. The results, presented in Figure 7, indicate that the sulfur-extended binder mixes exhibit an air voids vs. 

The permeability of the set sealant is measured by an API-recommended permeameter, which consists of a cylindrical sealant holder that is filled with the setting slurry. Once the slurry has set, the holder is fitted on a base. The base has an opening for gas connection, which can be attached to a nitrogen gas cylinder. Gas at different pressures is applied, and the pressure difference is measured by a mercury column. Knowing the pressure difference, the cross sectional area of the holder, and its length, one calculates the permeability in millidarcies. Details of such a permeameter and the procedure may be found in the API Spec. [3]. 

To determine groundwater flow at a site, hydraulic conductivity must be measured, either in a permeameter test in a laboratory or in situ. For the permeameter, or column, test (Fig. 3-6), aquifer material is placed in a labo-... 

FIGURE 3-6 A simple permeameter, or Darcy apparatus, used to measure hydraulic conductivity. The column, a pipe filled with the soil sample under test, has cross-sectional area A and length L specific discharge q is therefore equal to total column flow Q divided by A. Hydraulic conductivity K is estimated using Darcy s law K = —q/(Ah/L). In this apparatus, it is assumed that negligible head loss occurs in the hoses connecting the soil column to the constant head water reservoirs I and II and in the screens used to hold the soil in the column. 

Permeability and Deaeration Various states of fluidization and pneumatic conveying exist for bulk solid. Fluidization and aeration behavior may be characterized by a fluidization test rig, as illustrated in Fig. 21-25. A loosely poured powder is supported by a porous or perforated distributor plate. The quahty and uniformity of this plate are critical to the design. Various methods of filling have been explored to include vibration and vacuum fiUing of related permeameters... 

FIG. 21-25 iFluid" fluidization permeameter, illustrating powder bed supported by distributor plate fluidized at a gas velocity U, with associated pressure taps for multiple pressure gradient measurements dP/dh. Courtesy iPowder Systems, EhG, Associates, Inc.)... 

Figure 2.2 (a) Fixed head permeameter. (b) Falling head permeameter. 

Constant Head Permeameter Method (for Very Porous Soils)... 

Brass permeameters of about 7 cm inside diameter and 10 cm length with perforated bottoms. 

Take 200g of air-dry soil passed through a 2 mm sieve and dump the entire sample in one lot into the permeameter. 

Mix and pack the sample by tapping the permeameter 15-20 times on a wooden block through a height of 2.5 cm. 

Saturate the soil by placing the permeameter in a tray filled with water in such a way that the water level is slightly above the bottom of the samples. 

Place the permeameter on the stand and start the siphon to ensure a constant head of 2-3 cm of water on the top of the soil by siphon tubes and Mariotte arrangement. 

Diameter of the permeameter Cross-sectional area of the permeameter Depth of water above the soil... 

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