Analysis of a drawdown test displaying the use of transparent soil in unsaturated flow applications

Siemens, Greg; Peters, S. B.; Take, W. Andrew

doi:10.1201/b10526-114

Cited by 8 publications

(10 citation statements)

References 0 publications

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“…Light diffusers were used to disperse LED hotspots to ensure uniform illumination of the water bath and submerged soil chamber. Precursor trial tests confirmed that large variations in pixel intensity, as reported by Siemens et al (2010) and Peters et al (2011), did not occur and hence confirmed the suitability of the control measures implemented to minimize pixel intensity variation caused by poor illumination.…”

Section: Test Apparatussupporting

confidence: 56%

“…This is significantly lower than the maximum deviation of approximately 50 pixels reported by Peters et al (2010); however, it still represents a potential error over the pixel range. Any variation in pixel intensity will have a detrimental effect on the interpretation of temperatures using an image-based measure detection system.…”

Section: Figcontrasting

confidence: 38%

“…The success of transparent soil modeling has long been considered reliant on producing a soil surrogate that offers the highest optical clarity, with low transparency being considered detrimental to the modeling technique (Black and Take 2015). However, recent work by Siemens et al (2010) and Peters et al (2011) embraced the loss of soil transparency as a positive characteristic for the purpose of modeling unsaturated soil phenomena. The authors appreciated that fused quartz soil particles appeared white in color when dry, yet were invisible when submerged in suitably matched refractive index pore fluid (i.e., 100 % saturation), so that a uniform black background behind the soil would be clearly visible.…”

Section: Transparent Soil Modelingmentioning

confidence: 99%

“…Moreover, individual pixels located on the camera charged couple device (CCD) sensor will be subjected to varying light intensity owing to the ability of the lens to focus light. Siemens et al (2010) and Peters et al (2011) encountered significant challenges when interpreting and correlating pixel intensity to saturation level as the experiment was illuminated using standard fluorescent room lighting and required the use of multiple cameras with overlapping fields of view. Hence, normalization of the pixel intensity was necessary to account for variations in illumination in the field of view due to the poor lighting conditions.…”

Section: Figmentioning

confidence: 99%

“…The background (referred to herein as "calibration target") implemented in the current research consisted of two distinct regions: (i) black uniform intensity and (ii) alternating black and white stripes at a spatial frequency of 1 line pair per mm (lp/mm). This split target was adopted due to the positive outcome in the work of Siemens et al (2010) and Peters et al (2011), who reported success using a black uniform background to detect changes in pixel intensity to capture loss of optical transmission, and striped region due to complementary work by Black and Take (2015) that established a robust quantitative framework for assessing the optical quality of transparent soils using optical method referred to as "modulation transfer function" (MTF). MTF operates by relating the pixel contrast that is transferred from an object to an image and is commonly used to calibrate optical systems.…”

Section: Figmentioning

confidence: 99%

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Transparent Soil to Model Thermal Processes: An Energy Pile Example

Black

Tatari

2015

Geotech. Test. J.

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Managing energy resources is fast becoming a crucial issue of the 21st century, with groundbased heat exchange energy structures targeted as a viable means of reducing carbon emissions associated with regulating building temperatures. Limited information exists about the thermo-dynamic interactions of geothermal structures and soil owing to the practical constraints of placing measurement sensors in proximity to foundations; hence, questions remain about their long-term performance and interaction mechanics. An alternative experimental method using transparent soil and digital image analysis was proposed to visualize heat flow in soil. Advocating the loss of optical clarity as a beneficial attribute of transparent soil, this paper explored the hypothesis that temperature change will alter its refractive index and therefore progressively reduce its transparency, becoming more opaque. The development of the experimental methodology was discussed and a relationship between pixel intensity and soil temperature was defined and verified. This relationship was applied to an energy pile example to demonstrate heat flow in soil. The heating zone of influence was observed to extend to a radial distance of 1.5 pile diameters and was differentiated by a visual thermal gradient propagating from the pile. The successful implementation of this technique provided a new paradigm for transparent soil to potentially contribute to the understanding of thermo-dynamic processes in soil.

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Section: Test Apparatussupporting

confidence: 56%

Section: Figcontrasting

confidence: 38%

Section: Transparent Soil Modelingmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

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Transparent Soil to Model Thermal Processes: An Energy Pile Example

Black

Tatari

2015

Geotech. Test. J.

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Comparison of confined and unconfined infiltration in transparent porous media

Siemens

Peters

Take

2013

Water Resources Research

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[1] Infiltration is often assumed to occur with little or no impedance from the air within the vadose zone. If this assumption is not valid air counterflow may occur, while the infiltration rate and degree of saturation within the transmission zone may be significantly reduced. Accurate predictions of infiltration rates are important for applications such as moisture balance calculations and predictions of pore water pressures in landslide triggering. Existing results for confined infiltration show contradictory evidence for either air pressure remaining at a threshold or continual increase of air pressure. In this paper, the effect of air entrapment is investigated in the laboratory using recently developed techniques of unsaturated transparent porous media and digital photograph interpretation. These techniques enable the full saturation profile to be quantified every 5 s. The experimental data are used to quantify the decrease in infiltration rate and degree of saturation within the transmission zone in the confined infiltration, to accurately locate the wetting front, and to assess the stability of the wetting front. The results confirm previous observations in which infiltration in an open system was observed to occur significantly faster than in a closed system. However, in this study, the air pressure ahead of the wetting front was observed to reach a threshold value, which was a function of the ponding height and suction at the wetting front. A Green-Ampt infiltration model based on this observation of air confinement was observed to provide a better fit to the experimental data than the one based on the continual increase in air pressure assumption.

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