An Image-Based Method for Determining Bulk Density and the Soil Shrinkage Curve

Stewart, Ryan D.; Najm, Majdi Abou; Rupp, David E.; Selker, John S.

doi:10.2136/sssaj2011.0276n

Cited by 32 publications

(22 citation statements)

References 23 publications

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“…Currently, only a few methods enable the simultaneous determination of the shrinkage behavior of soil samples in combination with the quantification of the corresponding soil hydraulic properties. Either the methods need proprietary software for data processing, the used equipment is expensive or the calculation of the hydraulic properties is executed by inverse modelling ( Stewart et al, 2012). The objective of this study was to develop an alternative, simplified method for the simultaneous and automatic determination of (1) the shrinkage behavior, (2) the water retention curve (pF), and (3) the unsaturated hydraulic conductivity function (K).…”

Section: Introductionmentioning

confidence: 99%

Simplified method for quantifying the hydraulic properties of shrinking soils

Schindler

Doerner

Mueller

2015

J. Plant Nutr. Soil Sci.

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In general, soils and their pore size systems are assumed to be rigid during the loss of water on drying. In reality, it is not the case for most soils, especially for soils with high quantities of clay or organic matter. As a result of shrinking, there are changes in the bulk density, the porosity, the pore size distribution, and the hydraulic properties of these soils. Currently, only a few methods enable the shrinkage behavior of soil samples to be determined while simultaneously quantifying the corresponding soil hydraulic properties. Either the methods need proprietary software for data processing, the equipment used is expensive or the calculation of the hydraulic properties is executed by inverse modelling. The aim of this study was to develop an alternative, simplified method for the simultaneous and automatic determination of the soil hydraulic properties, taking shrinkage into account. The HYPROP® evaporative device was combined with a circumference meter. A preliminary investigation found that the diameter of the cylindrical samples used for the HYPROP decreased linearly during evaporation from the bottom to the top. To sum up, recording the perimeter change in the middle position of the sample during drying‐out, together with the corresponding tension and water content, was sufficient to determine the hydraulic functions taking shrinkage into account. Measurements are presented for 6 samples which are different in texture and geological origin. The maximum shrinkage (19.5% by vol. between saturation and 5,000 hPa) was measured in the peat samples. The minimum shrinkage was quantified at 0.68% by vol. for the silty loam samples from Chile. The advantages of the method presented are: (1) the water retention curve and the hydraulic conductivity function can be determined simultaneously in the range between saturation and close to the wilting point, at a high resolution and taking into consideration shrinkage; (2) the method and device are simple and robust to use; (3) little time is required for measurement, between 3 and at most 10 d; (4) the functions are described over the whole tension range, using more than 100 user‐defined data points; (5) the evaluation of the volumetric soil water content measurement in shrinking soils is improved; and (6) common data models can be fitted to the hydraulic data as well as to the shrinkage data.

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Section: Introductionmentioning

confidence: 99%

Simplified method for quantifying the hydraulic properties of shrinking soils

Schindler

Doerner

Mueller

2015

J. Plant Nutr. Soil Sci.

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“…While, in the rubber balloon method, reconstituted soil cores were used in most studies (Tariq and Durnford, 1993a;Cornelis et al, 2006). In this approach, the soil samples were submerged into water and then the change in the sample volume was determined from the volume of displaced fluid; (ii) physical measurement-based approach: where the soil cores "disturbed or undisturbed" dimensions were measured directly using a vernier caliper (Berndt and Coughlan, 1977;Huang et al, 2011), a linear displacement transducer (Boivin et al, 2004;Braudeau and Mohtar, 2004) or a thin metal stick (Kim et al, 1992); (iii) laser sensors-based approach: where the soil core diameter and height were determined through laser beams such as the retractometer apparatus (Braudeau et al, 1999), (iv) imagebased approach: where the volume of the soil sample (either clod or core) was either scanned with a 3-D optical scanner (Sander and Gerke, 2007) or by a simple standard digital camera (Stewart et al, 2012). Several studies have discussed and compared these methods, Cornelis et al (2006) showed that there were significant differences between the Archimedes' principlebased methods "paraffin-coated and rubber balloon methods" and the physical measurement-based methods "vernier caliper method" where the former produced more accurate and reliable data; however, Sander and Gerke (2007) observed some errors in the resin-coated method that affects the measured volume due to inadequate coating or penetration of the coating materials.…”

Section: Introductionmentioning

confidence: 99%

Physics of the soil medium organization part 2: pedostructure characterization through measurement and modeling of the soil moisture characteristic curves

Assi

Braudeau

Accola

et al. 2014

Front. Environ. Sci.

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“…Based on the water displacement, the volume of the soil sample is determined. The disadvantage of this rubber balloon method is that the soil sample is usually disturbed when packed into the rubber balloon [130], which influences the accuracy of the volume determination. Further, the general disadvantage of all techniques based on Archimedes' principle is that the sample is not reusable after applying this method.…”

Section: Review Of Available Methodsmentioning

confidence: 99%

“…Each volume determination requires a new single specimen. This implies that numerous specimens are needed to determine, for example, the entire shrinkage curve [130]. In addition, it is nearly impossible to prepare several soil samples with exactly the same initial test conditions in terms of water content, density and so forth.…”

Section: Review Of Available Methodsmentioning

confidence: 99%

“…Similar to [131], Schafer and Singer [132] measured the length of a rod-shaped soil sample under shrinkage using a calliper. The major disadvantage of measuring the soil sample dimension is that axis-symmetric volume changes are typically assumed [130]; hence, the volume determination of the irregular sample shapes is complicated.…”

Section: Review Of Available Methodsmentioning

confidence: 99%

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Mechanical, hydraulic, and dielectric characterisation of fine-grained soils during densification

Schwing¹

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Soil characterisation is of primary interest for several disciplines, including geotechnical and geo-environmental engineering, soil science, and agriculture. An upcoming and promising method for soil characterisation relies on the high-frequency electromagnetic measurement technique which provides the potential to explore and investigate soils. However, successful application of this technique requires a profound understanding of the multi-physical processes arising from interactions between soil as a porous medium and the propagation of electromagnetic waves. This thesis focuses on a coupled experimental investigation of the mechanical, hydraulic, and dielectric characterisation of fine-grained soil during densification.In the framework of this thesis, the following steps have been completed and novel findings have been made:1. Probe designs have been developed, modified and improved to measure the dielectric soil properties in a frequency range from 1 MHz to 3 GHz during shrinkage and compaction. A low-cost in-house-manufactured probe was introduced, which was specifically designed for standardised geotechnical soil shrinkage test. During preliminary investigations, the calibration procedure and performance of these sensors were experimentally and numerically tested. The results showed agreement in the targeted frequency window.2. Compaction and shrinkage tests on fine-grained soils were conducted in combination with dielectric and soil suction measurements. The shrinkage curve and soil water characteristic curve (SWCC) was established and successfully parameterised with physical based models. The complex permittivity was determined in a frequency range from 1 MHz to 3 GHz. The dielectric properties measured during the shrinkage test showed a sudden drop of complex permittivity which could be located in the residual shrinkage zone.3. A theoretical electromagnetic mixture approach was used to model the measured frequency dependent dielectric properties of soils during shrinkage and compaction based on the parameterised shrinkage curve and SWCC. The theoretical results were compared to the dielectric measurements on different fine-grained soils. The comparison ii showed that the real part of permittivity could be well predicted whereas the imaginary part suffered inaccuracies.4. A sensitivity analysis was performed with the theoretical electromagnetic mixture approach in consideration of the shrinkage behaviour and SWCC in order to investigate the influence of soil suction and dry density on the frequency dependent permittivity.The sensitivity analysis showed that the real part of the permittivity near 1 GHz was insensitive to changes in the soil suction and dry density. In the MHz range, the real part of the permittivity was more sensitive to changes in soil suction than it was to dry density. The imaginary part of the permittivity was generally observed to be more sensitive to soil suction over the entire frequency range.

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An Image-Based Method for Determining Bulk Density and the Soil Shrinkage Curve

Cited by 32 publications

References 23 publications

Simplified method for quantifying the hydraulic properties of shrinking soils

Simplified method for quantifying the hydraulic properties of shrinking soils

Physics of the soil medium organization part 2: pedostructure characterization through measurement and modeling of the soil moisture characteristic curves

Mechanical, hydraulic, and dielectric characterisation of fine-grained soils during densification

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