Characterizing Nonrigid Aggregated Soil–Water Medium Using its Shrinkage Curve

Braudeau, Erik; Frangi, Jean-Pierre; Mohtar, Rabi H.

doi:10.2136/sssaj2004.0359

Cited by 57 publications

(92 citation statements)

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“…Transition from the shrinkage curve, U(w) of the intra-aggregate matrix to the contribution, U (w ) of the intra-aggregate matrix to the specific volume of an aggregate system (U a ) and soil (Y), for clay contents c<c , based on Eqs. (16)- (18). In particular, w z =w z /K, w n =w n /K, w h =w h /K.…”

Section: Contributions To the Total Water Content (W) And Volume (U Amentioning

confidence: 99%

“…All the current models of the soil shrinkage curve, at all the differences between them, are based on the approximation of the experimental shrinkage curve data by some a priori taken mathematical expression (different for each different approach) [10,11,[13][14][15][16][17][18][19][20]. Such expressions are not derived from considerations of the soil inter-and intraaggregate structure, but justified by the fitting of their parameters (from 3 to 11 depending on the approach) to the experimental shrinkage curve data.…”

Section: Introductionmentioning

confidence: 99%

“…Such expressions are not derived from considerations of the soil inter-and intraaggregate structure, but justified by the fitting of their parameters (from 3 to 11 depending on the approach) to the experimental shrinkage curve data. The a priori accepted mathematical approximation of a shrinkage curve can be useful for applications (e.g., [19,20]) and other aims (e.g., [18]). However, explanation and understanding of the characteristic features (see above (a) through (d)) of a soil shrinkage curve and their origin, implies qualitative or quantitative derivation of the shrinkage curve from inter-and intra-aggregate soil structure.…”

Section: Introductionmentioning

confidence: 99%

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Step-by-Step Transition from Clay to Soil Shrinkage Curve

Chertkov¹

2008

TOMECHJ

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Clay and soil containing it have shrinkage curves that are qualitatively different in shape. The objective of this work is to qualitatively show with maximum simplicity, how a clay shrinkage curve turns into a soil shrinkage curve. Because of the crack volume the measured shrinkage curve is not the single-valued feature of a soil. We use a concept of the reference shrinkage curve that is only stipulated by soil shrinkage without cracking, single-valued, and qualitatively similar to an observed shrinkage curve. We also use new concepts of an intra-aggregate soil structure: (i) a deformable, but non-shrinking surface layer of aggregates that loses water during shrinkage; and (ii) lacunar pores (micro-cracks) inside an intra-aggregate clay that increase in volume during shrinkage. Then, through a series of consecutive steps, illustrating each step by a separate graphic presentation, we move from a clay shrinkage curve to a soil shrinkage curve with predicted qualitative features that coincide with those experimentally observed in numerous soil shrinkage publications. We thereby demonstrate the qualitative physical impact of the intra-aggregate structure on soil shrinkage.

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Section: Contributions To the Total Water Content (W) And Volume (U Amentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Step-by-Step Transition from Clay to Soil Shrinkage Curve

Chertkov¹

2008

TOMECHJ

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“…In engineering science, the extent of soil shrinkage behaviour can be described by the shrinkage curve which gives the relationship between soil volume change and water content [83]. Different definitions of the shrinkage curve can be found in the literature; however, the most commonly used are as follows: [84,85] • ϑ − e -relationship [6,86] • ζ − ν -relationship [87] where, ϑ = w · ρ G /ρ W is the moisture ratio, e is the void ratio, ζ = w/w M is the relative water content given by the ratio of current water content to the maximum water content w M (e.g. Two aspects need to be highlighted and explained prior to further description of soil shrinkage behaviour:…”

Section: Soil Shrinkagementioning

confidence: 99%

“…A number of approaches and models have been proposed in previous research to predict soil shrinkage behaviour and describe the obtained experimental shrinkage curves [3,83,84,86,87,96,101,102,103]. Apart from the model of Chertkov [3,87], the currently available approaches are empirical fitting models that are based on approximation of the experimental shrinkage data.…”

Section: Shrinkage Curve Equationsmentioning

confidence: 99%

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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Mechanisms of lateral and linear extension of gullies (dongas) in a subhumid grassland of South Africa

Podwojewski

Janeau

Caquineau

et al. 2020

Earth Surf Processes Landf

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The formation of deep gullies (called 'dongas' locally) in rangeland in KwaZulu-Natal Province in South Africa is a natural phenomenon. These U-shaped, very wide gullies have considerable lateral expansion due to the episodic collapse of sidewalls. The dongas have developed in duplex soils such as Luvisols and Lixisols formed on Permian sedimentary rocks or unconsolidated Quaternary colluvium. This study combined morphological, mineralogical and chemical characterization with measurements of grain-size content, structural stability and the complete shrinkage curve to detect changes in soil properties of the different horizons located in the gully banks. The different soil horizons present clear and sharp differences in physical and mineralogical properties. The topsoil with complete grass cover is very resistant to soil detachment. However, the leached E horizon and the BC horizon have low structural stability. The soil profile down to and including the Bt horizon contains exclusively illite in the clay fraction, while the BC colluvial layer and the C horizon (mudstone) contain expandable interstratified illite-smectite. The Bt horizon has a high water content at saturation and high shrinkage, while the BC and C horizons have a high residual shrinkage and a very low water content at saturation. Because this type of gully expansion is not significantly linked to slope value or the stream power index (SPI) at the gully head, to land-use change, high rainfall intensities or the threshold of concentrated runoff being exceeded at the gully head, other causes were investigated. It was concluded that the heterogeneity between horizons with different mineralogical properties and structural stabilities, soil types and parent material, anisotropic water-saturation and shrink-swell properties are of major importance. This heterogeneity between different soil horizon morphologies and their physical properties can explain why the relationship between the critical slope and the drainage area for gully initiation showed a threshold for gullying much lower than that found elsewhere.

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Characterizing Nonrigid Aggregated Soil–Water Medium Using its Shrinkage Curve

Cited by 57 publications

References 0 publications

Step-by-Step Transition from Clay to Soil Shrinkage Curve

Step-by-Step Transition from Clay to Soil Shrinkage Curve

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

Mechanisms of lateral and linear extension of gullies (dongas) in a subhumid grassland of South Africa

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