The Experts below are selected from a list of 2856 Experts worldwide ranked by ideXlab platform
Okke Batelaan - One of the best experts on this subject based on the ideXlab platform.
-
the usefulness of outcrop analogue air permeameter measurements for analyzing aquifer heterogeneity quantifying outcrop hydraulic conductivity and its spatial variability
Hydrological Processes, 2014Co-Authors: Bart Rogiers, Koen Beerten, Tuur Smeekens, Matej Gedeon, Marijke Huysmans, Okke Batelaan, Dirk MallantsAbstract:Saturated hydraulic conductivity (K) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Although several well-established laboratory methods exist for determining K, in situ measurements of this parameter remain very complex and scale dependent. Often, the limited accessibility of subsurface sediments for sampling means an additional impediment to our ability to quantify subsurface K heterogeneity. One potential solution is the use of outcrops as analogues for subsurface sediments. This paper investigates the use of air permeameter measurements on outcrops of unconsolidated sediments to quantify K and its spatial heterogeneity on a broad range of sediment types. The Neogene aquifer in northern Belgium is used as a case study for this purpose. To characterize the variability in K, 511 small-scale air permeability measurements were performed on outcrop sediments representative over five of the aquifer's lithostratigraphic units. From these measurements, outcrop-scale equivalent K tensors were calculated using numerical upscaling techniques. Validation of the air permeameter-based K values by comparison with laboratory constant head K measurements reveals a correlation of 0.93. Overall, the results indicate that hand-held air Permeameters are very efficient and accurate tools to characterize saturated K, as well as its small-scale variability and anisotropy on a broad range of unconsolidated sediments. The studied outcrops further provided a qualitative understanding of aquifer hydrostratigraphy and quantitative estimates about K variability at the centimetre-scale to metre-scale. Copyright © 2013 John Wiley & Sons, Ltd.
-
high resolution saturated hydraulic conductivity logging of borehole cores using air permeability measurements
Hydrogeology Journal, 2014Co-Authors: Bart Rogiers, Koen Beerten, Matej Gedeon, Marijke Huysmans, Okke Batelaan, Dirk Mallants, P Winters, Alain DassarguesAbstract:Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. The hand-held air permeameter technique was investigated for high-resolution hydraulic conductivity determination on borehole cores using a spatial resolution of ∼0.05 m. The suitability of such air permeameter measurements on friable to poorly indurated sediments was tested to improve the spatial prediction of classical laboratory-based Ks measurements obtained at a much lower spatial resolution (∼2 m). In total, 368 Ks measurements were made on ∼350 m of borehole cores originating from the Campine basin, northern Belgium, while ∼5,230 air permeability measurements were performed on the same cores, resulting in a Ks range of seven orders of magnitude. Cross-validation demonstrated that, using air permeameter data as the secondary variable for laboratory based Ks measurements, the performance increased from R2 = 0.35 for ordinary kriging (laboratory Ks only) to R2 = 0.61 for co-kriging. The separate treatment of horizontal and vertical hydraulic conductivity revealed considerable anisotropy in certain lithostratigraphical units, while others were clearly isotropic at the sample scale. Air permeameter measurements on borehole cores provide a cost-effective way to improve spatial predictions of traditional laboratory based Ks.
Dassargues Alain - One of the best experts on this subject based on the ideXlab platform.
-
The usefulness of outcrop analogue air permeameter measurements for analyzing aquifer heterogeneity: quantifying outcrop hydraulic conductivity and its spatial variability
'Wiley', 2013Co-Authors: Rogiers Bart, Huysmans Marijke, Beerten Koen, Mallants Dirk, Batelaan Okke, Smeekens Tuur, Gedeon Matej, Dassargues AlainAbstract:peer reviewedaudience: researcher, professionalSaturated hydraulic conductivity (K) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Although several well-established laboratory methods exist for determining K, in situ measurements of this parameter remain very complex and scale dependent. Often, the limited accessibility of subsurface sediments for sampling means an additional impediment to our ability to quantify subsurface K heterogeneity. One potential solution is the use of outcrops as analogues for subsurface sediments. This paper investigates the use of air permeameter measurements on outcrops of unconsolidated sediments to quantify K and its spatial heterogeneity on a broad range of sediment types. The Neogene aquifer in northern Belgium is used as a case study for this purpose. To characterize the variability in K, 511 small-scale air permeability measurements were performed on outcrop sediments representative over five of the aquifer’s lithostratigraphic units. From these measurements, outcrop-scale equivalent K tensors were calculated using numerical upscaling techniques. Validation of the air permeameter-based K values by comparison with laboratory constant head K measurements reveals a correlation of 0.93. Overall, the results indicate that hand-held air Permeameters are very efficient and accurate tools to characterize saturated K, as well as its small-scale variability and anisotropy on a broad range of unconsolidated sediments. The studied outcrops further provided a qualitative understanding of aquifer hydrostratigraphy and quantitative estimates about K variability at the centimetre-scale to metre-scale
-
The usefulness of outcrop analogue air permeameter measurements for analyzing aquifer heterogeneity: quantifying outcrop hydraulic conductivity and its spatial variability
'Wiley', 2013Co-Authors: Rogiers Bart, Huysmans Marijke, Beerten Koen, Mallants Dirk, Batelaan Okke, Smeekens Tuur, Gedeon Matej, Dassargues AlainAbstract:Saturated hydraulic conductivity (K) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Although several well-established laboratory methods exist for determining K, in situ measurements of this parameter remain very complex and scale dependent. Often, the limited accessibility of subsurface sediments for sampling means an additional impediment to our ability to quantify subsurface K heterogeneity. One potential solution is the use of outcrops as analogues for subsurface sediments. This paper investigates the use of air permeameter measurements on outcrops of unconsolidated sediments to quantify K and its spatial heterogeneity on a broad range of sediment types. The Neogene aquifer in northern Belgium is used as a case study for this purpose. To characterize the variability in K, 511 small-scale air permeability measurements were performed on outcrop sediments representative over five of the aquifer’s lithostratigraphic units. From these measurements, outcrop-scale equivalent K tensors were calculated using numerical upscaling techniques. Validation of the air permeameter-based K values by comparison with laboratory constant head K measurements reveals a correlation of 0.93. Overall, the results indicate that hand-held air Permeameters are very efficient and accurate tools to characterize saturated K, as well as its small-scale variability and anisotropy on a broad range of unconsolidated sediments. The studied outcrops further provided a qualitative understanding of aquifer hydrostratigraphy and quantitative estimates about K variability at the centimetre-scale to metre-scale.Peer reviewe
-
Centimeter-scale secondary information on hydraulic conductivity using a hand-held air permeameter on borehole cores
2012Co-Authors: Rogiers Bart, Winters P., Huysmans Marijke, Beerten Koen, Mallants Dirk, Gedeon Mattej, Batelaan Okke, Dassargues AlainAbstract:Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Determining the small-scale variability of this parameter is key to evaluate implications on effective parameters at the larger scale. Moreover, for stochastic simulations of groundwater flow and contaminant transport, accurate models on the spatial variability of Ks are very much needed. While several well-established laboratory methods exist for determining Ks, investigating the small-scale variability remains a challenge. If several tens to hundreds of metres of borehole core has to be hydraulically characterised at the centimetre to decimetre scale, several hundreds to thousands of Ks measurements are required, which makes it very costly and time-consuming should traditional methods be used. With reliable air Permeameters becoming increasingly available from the late 80’s, a fast and effective indirect method exists to determine Ks. Therefore, the use of hand-held air permeameter measurements for determining very accurate small-scale heterogeneity about Ks is very appealing. Very little is known, however, on its applicability for borehole cores that typically carry a small sediment volume. Therefore, the method was tested on several borehole cores of different size, originating from the Campine basin, Northern Belgium. The studied sediments are of Miocene to Pleistocene age, with a marine to continental origin, and consist of sand to clayey sand with distinct clay lenses, resulting in a Ks range of 7 orders of magnitude. During previous studies, two samples were taken from borehole cores each two meters for performing constant head lab permeameter tests. This data is now used as a reference for the air permeameter measurements that are performed with a resolution of 5 centimetres. Preliminary results indicate a very good correlation between the previously gathered constant head Ks data and the air permeability measurements, but a systematic bias seems to exist. A geostatistical analysis with cross-validation is performed to assess the predictive uncertainty on Ks, using both types of data. We conclude that performing hand-held air permeameter measurements on undisturbed borehole cores provides a very cost-effective way to obtain very detailed information in the framework of stochastic simulation and conditioning of heterogeneous hydraulic conductivity fields
-
Centimeter-scale secondary information on hydraulic conductivity using a hand-held air permeameter on borehole cores
2012Co-Authors: Rogiers Bart, Winters P., Huysmans Marijke, Beerten Koen, Mallants Dirk, Gedeon Mattej, Batelaan Okke, Dassargues AlainAbstract:audience: researcher, professionalSaturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Determining the small-scale variability of this parameter is key to evaluate implications on effective parameters at the larger scale. Moreover, for stochastic simulations of groundwater flow and contaminant transport, accurate models on the spatial variability of Ks are very much needed. While several well-established laboratory methods exist for determining Ks, investigating the small-scale variability remains a challenge. If several tens to hundreds of metres of borehole core has to be hydraulically characterised at the centimetre to decimetre scale, several hundreds to thousands of Ks measurements are required, which makes it very costly and time-consuming should traditional methods be used. With reliable air Permeameters becoming increasingly available from the late 80’s, a fast and effective indirect method exists to determine Ks. Therefore, the use of hand-held air permeameter measurements for determining very accurate small-scale heterogeneity about Ks is very appealing. Very little is known, however, on its applicability for borehole cores that typically carry a small sediment volume. Therefore, the method was tested on several borehole cores of different size, originating from the Campine basin, Northern Belgium. The studied sediments are of Miocene to Pleistocene age, with a marine to continental origin, and consist of sand to clayey sand with distinct clay lenses, resulting in a Ks range of 7 orders of magnitude. During previous studies, two samples were taken from borehole cores each two meters for performing constant head lab permeameter tests. This data is now used as a reference for the air permeameter measurements that are performed with a resolution of 5 centimetres. Preliminary results indicate a very good correlation between the previously gathered constant head Ks data and the air permeability measurements, but a systematic bias seems to exist. A geostatistical analysis with cross-validation is performed to assess the predictive uncertainty on Ks, using both types of data. We conclude that performing hand-held air permeameter measurements on undisturbed borehole cores provides a very cost-effective way to obtain very detailed information in the framework of stochastic simulation and conditioning of heterogeneous hydraulic conductivity fields
-
Air permeametry on outcrop analogues: a composite image of the Neogene aquifer, Belgium
2012Co-Authors: Rogiers Bart, Huysmans Marijke, Mallants Dirk, Gedeon Mattej, Batelaan Okke, Beerten K., Smekens T., Dassargues AlainAbstract:audience: researcher, professionalSaturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. While several well-established laboratory methods exist for determining Ks, in-situ measurements of this parameter remain very complex. Since the 50’s, and increasingly from the late 80’s, air Permeameters are being used effectively as an indirect method to determine Ks on outcrop sediments. In this paper, the heterogeneity within outcrop sediments that are analogues for the Neogene aquifer hydrostratigraphic units in northern Belgium is studied with a hand-held air permeameter. This aquifer, representing a major groundwater source, consists of several sandy geological units from Miocene to Pleistocene age with a marine to continental origin. Moreover, it plays an important role in the Belgian deep geological radwaste disposal studies, and is the subject of a safety assessment for a future low-level radwaste surface repository. To characterise the variability between and within the different lithostratigraphical aquifer units, 804 air permeability measurements at cm-scale were performed on several outcrops that are analogues for the sandy aquifer sediments and a highly heterogeneous aquitard. Equivalent meter-scale Ks tensors were calculated numerically through the law of flow conservation to obtain the vertical anisotropy factor. The off-diagonal tensor components were shown to be negligible. To validate the air permeametry data, 18 additional constant head permeameter tests on 100 cm3 cores and 27 grain size analyses based Ks assessments were performed on outcrop material. The comparison indicates that hand-held air Permeameters are very effective and useful tools to characterise the magnitude of hydraulic conductivity, as well as it’s small-scale variability and anisotropy, on a broad range of sediment types. However, a comparison with data from a previous borehole campaign on similar though not identical aquifer sediments reveals that the Ks values predicted at the outcrops are systematically higher by at least a factor of 10 than the corresponding Ks distributions determined from the borehole cores. One explanation is the weathering state of several-cm thick clay lenses, i.e. much less weathered in the aquitard than in the analogous outcrop with correspondingly lower conductivities for the aquitard. This shows that transferring outcrop data to the subsurface should be done with care because of different degrees of compaction, weathering states, etc
John V Prodan - One of the best experts on this subject based on the ideXlab platform.
-
swept frequency Permeameters for measuring the complex off diagonal permeability tensor components of anisotropic thin magnetic films
Journal of Applied Physics, 1993Co-Authors: Craig A Grimes, John V ProdanAbstract:To better understand wave propagation through magnetic media we have measured the high‐frequency off‐diagonal permeability tensor components of magnetic thin films using a thin‐film permeameter. Although the off‐diagonal components are commonly considered to be of negligible value, for some materials they are substantial, of a magnitude comparable to that of the diagonal terms. Since the out‐of‐plane off‐diagonal coupling terms are primarily imaginary below resonance, and real above, they may introduce unexpected phase errors into the read/write process of magnetic recording and bulk material measurements and are therefore worthy of attention. The Permeameters used to measured the off‐diagonal terms are based upon the design of C. A. Grimes, P. L. Trouilloid, and R. M. Walser [IEEE Trans. Magn. MAG‐24, 603 (1988)], which measure diagonal terms, but with different pickup coil and sample seat geometries. For z normal to the film, and with x and y defining, respectively, the hard and easy magnetization axes ...
Ingmar Messing - One of the best experts on this subject based on the ideXlab platform.
-
Infiltration Rate and Hydraulic Conductivity Measured with Rain Simulator and Disc Permeameter on Sloping Arid Land
Arid Land Research and Management, 2010Co-Authors: A. Joel, Ingmar MessingAbstract:The objective of the study was to examine relationships between steady infiltration rates and hydraulic conductivity obtained with drip infiltrometer and disc permeameter on moderately to strongly sloping land. The disc permeameter is generally used for measurements on horizontal or slightly sloping surfaces but is easier to handle in the field than the drip infiltrometer. At two sites on natural prairie in Central Chile, a portable drip infiltrometer was used to measure infiltration rate and simulate rain, including the impact of falling drops, using two strategies: (1) DIH starting with a high application rate and decreasing it until a minimal application rate that generated steady runoff was obtained, and, (2) DIL starting with a low rate and increasing it until steady infiltration rate that did not increase was ensured. In parallel, a disc permeameter was used to determine infiltration rate (PI) and hydraulic conductivity (K) at different supply water pressure heads ( ). Infiltration rates obtained ...
-
Application of two methods to determine hydraulic conductivity with disc Permeameters on sloping land
European Journal of Soil Science, 2000Co-Authors: A. Joel, Ingmar MessingAbstract:Summary The purpose of the present study was to compare two methods for estimating the hydraulic conductivity near saturation with disc Permeameters, and to identify their merits when studying runoff on sloping land. The soil's hydraulic conductivity (K) was measured with disc Permeameters at a sequence of nominal pressures (ψ) in three blocks with average slope gradients of 11.0% (two occasions), 21.5% (two occasions) and 29.3% (one occasion), respectively, within a sloping area, 40 m wide and 100 m long. Two different methods were used. In the first, the split-location method, the permeameter was moved to an adjacent spot after measurement at each applied ψ. The estimate of K(ψ) was based on measured sorptivity, steady-state volumetric flow, initial volumetric water content and the volumetric water content at the applied ψ. In the second method, the one-location method, the permeameter was not moved during the measurements at each sequence of applied ψ and the estimate of K(ψ) was based only on steady-state volumetric flow and piece-wise application of the exponential relation between K and ψ. The latter method generally gave smaller estimates of K than the former on the gentle slopes. These differences were smaller or negligible on steeper slopes. The slope gradient and the conditions in the uppermost soil layers had a definite influence on the values of K obtained. The one-location method is recommended in studies in which disturbance of the soil surface must be kept to a minimum, as is the case in experimental plots.
Craig A Grimes - One of the best experts on this subject based on the ideXlab platform.
-
surface permeameter for nondestructive measurement of the rf complex permeability spectra of thin surface coatings
Review of Scientific Instruments, 1996Co-Authors: Craig A GrimesAbstract:Thin film permeability measurement techniques such as stripline cavities or conventional Permeameters require the sample undergoing measurement to be inserted within a fixture; typically, these samples can be no larger than a few square inches. However, certain applications require knowledge of the complex permeability of a coating or film applied to a finished, large product such as films deposited onto a continuous web for use as identification markers, the inside of a computer case for the control of EMI, or a ship mast for reduction of radar reflections. Therefore, a surface permeameter is presented that measures the rf complex permeability spectra of continuous films or coatings that are placed adjacent to the fixture over the frequency range of 10–500 MHz.
-
swept frequency Permeameters for measuring the complex off diagonal permeability tensor components of anisotropic thin magnetic films
Journal of Applied Physics, 1993Co-Authors: Craig A Grimes, John V ProdanAbstract:To better understand wave propagation through magnetic media we have measured the high‐frequency off‐diagonal permeability tensor components of magnetic thin films using a thin‐film permeameter. Although the off‐diagonal components are commonly considered to be of negligible value, for some materials they are substantial, of a magnitude comparable to that of the diagonal terms. Since the out‐of‐plane off‐diagonal coupling terms are primarily imaginary below resonance, and real above, they may introduce unexpected phase errors into the read/write process of magnetic recording and bulk material measurements and are therefore worthy of attention. The Permeameters used to measured the off‐diagonal terms are based upon the design of C. A. Grimes, P. L. Trouilloid, and R. M. Walser [IEEE Trans. Magn. MAG‐24, 603 (1988)], which measure diagonal terms, but with different pickup coil and sample seat geometries. For z normal to the film, and with x and y defining, respectively, the hard and easy magnetization axes ...