Soil Shrinkage Curve Research Articles

Coupled hydro‐mechanical pore‐scale modeling of biopore‐coated clods for upscaling soil shrinkage and hydraulic properties

AbstractEarthworms and plant roots are vital for macropore formation and stabilization. The organo‐mineral coating of biopore surfaces also regulates macropore‐matrix mass exchange during preferential flow. The influence of finer‐textured burrow coatings on macroscopic soil properties during shrinkage could potentially be assessed by upscaling pore‐scale hydraulic and mechanical simulations. The aim was to investigate the influence of micro parameters (particle size, stiffness, and bond strength) on macro parameters (i.e., shrinkage curve and soil hydraulic properties). Drainage experiments and simulations were carried out using biopore‐coated clod‐size samples compared to those without coating. Simulations were performed using a two‐phase pore‐scale finite volume coupled with discrete element model (DEM‐2PFV). The structural dynamics was characterized by analyzing the pore volume and soil shrinkage curve obtained from numerically determined data. The soil hydraulic parameters were described using uni‐ and bimodal van Genuchten (vG) functions. The drainage simulations revealed hydro‐mechanical dynamics characterized by Braudeau‐shrinkage curve subdomains: The matrix‐only samples, with lower particle bond strength, exhibited relatively higher shrinkage. The coated samples, with higher particle stiffness and bond strength, displayed greater hydro‐mechanical stability. The numerically determined initial value of the saturated hydraulic conductivity (Ks) was about 70 times larger for matrix‐only samples than for coated samples. As expected, for the nonrigid soil structures, constant Ks, α, and n values for bimodal vG model resulted in prediction errors. Upscaling DEM‐2PFV pore‐scale model outcomes quantifies micro‐coating effects on macro hydro‐mechanics. This yields void ratio‐based soil water retention and hydraulic conductivity functions, advancing macroscopic soil hydraulic models and enhancing structured soil flow and transport descriptions.

Evaluating the role of soil properties on volumetric shrinkage characteristics of marine and inland clays

ABSTRACT Clayey soils that exhibit swelling and shrinkage behaviour have paved the way for various engineering problems such as foundation failure, slope stability issues, failure of earthen dams, cracking of clay liners, etc. The shrinkage behaviour of soil is often quantified by employing various direct and indirect experimental techniques to establish the Soil Shrinkage Curve (SSC), a relationship between soil volume change and moisture content. However, SSC can reveal only the overall volume change and does not exclusively comprehend the variation of volumetric shrinkage in linear and radial directions. Hence, a series of desiccation tests were performed on marine and inland clayey soils of different consistencies to evaluate the contribution of volumetric shrinkage in these orientations. From this study, it has been observed that the linear component of volumetric shrinkage was higher for soil samples with a consistency state between 1.0 and 1.5 times the liquid limit. However, the radial component of volumetric shrinkage was found to be higher at the end of the desiccation test for soils with an initial moisture content at or below the liquid limit. Furthermore, the results obtained from the present study have been utilised to establish the influence of soil properties on radial, linear, and total volumetric shrinkage.

Mechanical and thermal properties of mud dauber nests under atmospheric drying

Mud dauber wasps construct soil nests to protect their offspring from predators, extreme temperatures, and rainwater. The mechanical and thermal properties of these nests are important for the reproductive success of mud daubers. The previous study showed that the high densities and strengths of mud dauber nests were due to the repetitive tapping and atmospheric drying used by mud daubers during nest construction. This study investigated the effect of atmospheric drying on the mechanical and thermal properties of mud dauber nests. The soil shrinkage curve, elastic modulus, suction stress characteristic curve, soil water retention curve, shear strength, and thermal conductivity function of mud dauber nest soils were measured by performing drying cake tests, direct shear tests, unconfined compression tests, and thermal conductivity measurements. This study showed atmospheric drying could increase Young’s moduli (from hundreds to thousands of kPa), the magnitudes of suction stress (up to 64 kPa), and shear strengths (e.g., unconfined compressive strength increased up to 2100 kPa) of mud dauber nests. The thermal conductivity was reduced by 47% due to atmospheric drying. Investigation of mud dauber nests under atmospheric drying could provide insights and inspiration to improve human manufacturing and manipulation of soils for earthen building construction.

Evaluating innovative direct and indirect soil suction and volumetric measurement techniques for the determination of soil water retention curves following drying and wetting paths

Soil Water Retention Curves (SWRC) are a main characterising component in constitutive models developed for describing unsaturated soils behaviour. Their determination requires establishing a combination of accurate soil matric suction measurements and volumetric measurements. While direct suction methods are always preferred, current methods, such as high capacity tensiometers, are limited to a measuring range of only 1.5 MPa. In this work, the novel Northumbria High Capacity Tensiometer, with an extended measuring range of up to 3.5 MPa, is used in a simplified continuous-drying setup, with proposed modifications to enhance the equalisation times and volumetric measurements. The results are then compared and validated with direct and indirect methods in both drying and wetting paths. At the same time, different volumetric measurement techniques were assessed in order to establish an understanding of Soil Shrinkage Curves (SSCs) that describe the moisture-voids relationship during drying and wetting and has the potential to be used for indirect determination of volumetric dimensions of soil specimens. Hysteresis was observed in the water retention behaviour but not in the volumetric behaviour. An established SSC model is proposed in this work and is fitted to experimental data in order to indirectly estimate volumetric measurements from the water content of small-scale specimens. The proposed novel approach standardises volumetric measurements determination, leading to uniform and complete-range SWRCs.

Influence of compaction on the soil shrinkage and swelling curves

The behaviour of soils undergoing deformation due to changes in water content can be described using Soil Shrinkage Curves (SSCs). The SSCs are normally influenced by several factors as the soil’s fabric, different compaction levels, residual void ratio, and the shrinkage limit. In this study, shrinkage curves at different compaction levels were obtained using both wax coating and image analysis as volumetric quantification methods. Both techniques returned consistent results. To fit the obtained experimental data, a single equation is proposed with fitting parameters pertaining to the physical characteristics of the soil samples used. The use of Mercury Intrusion Porosimetry (MIP) is also incorporated to further analyse the structure of the soils being studied. The effect of the drying path on the structure was more apparent in the size range of 100-2000 nm. The effects of compaction on soil structure and shrinkage behaviour were also discussed in the study. The presented work provides valuable insights on the effect of different compaction levels on the soil shrinkage behaviour.

In-situ assessment of soil shrinkage and swelling behavior and hydro-thermal regimes with a thermo-time domain reflectometry technique

The shrinkage and swelling behaviors of clayey soils could lead to cracks and erosions inducing severe damages to agricultural lands and engineering projects. Thus, improving the understanding of shrink-swell characteristics is crucial to nonrigid soils. However, it remains difficult for in-situ monitoring of soil shrink-swell processes continuously and nondestructively. The objective of this study was to present a thermo-time domain reflectometry (thermo-TDR) technique for determination of soil shrinkage and swelling dynamics and hydro-thermal regimes in-situ during wet-dry cycles. A field experiment on two clayey soils (a paddy soil and an alluvial soil) was conducted to evaluate the performance of the thermo-TDR method for in-situ determination of soil volume changes and associated hydraulic and thermal properties during wet-dry cycles. The results showed that both soils experienced considerable shrinking and swelling processes with maximum vertical deformations of 2.4 and 1.8 cm for the paddy soil and alluvial soil, respectively, and with maximum horizontal deformations of 370 and 280 cm2 for the paddy soil and alluvial soil, respectively, during a 36-day period. The thermo-TDR method provided volume change values (shown as the bulk density) agreed well with independent core-sampling measurements with an average RMSE of 0.15 Mg m−3 and a R2 of 0.46. A better agreement was observed between thermo-TDR measured bulk densities and values from the ruler-image processing method with an average RMSE of 0.07 Mg m−3 and a R2 of 0.77. Besides, the thermo-TDR method gave consistent in-situ soil shrinkage curve and water retention surface measurements by combining with soil matric potential sensors. Unlike rigid soils, the paddy and alluvial soils showed complicated hydro-thermal regimes in response to the shrink-swell processes. We conclude that the thermo-TDR technique is a reliable tool for continuous in-situ determination of soil shrink-swell processes. Future studies should focus on development of comprehensive soil heat and water transport models accounting for both moisture content and volume changes.

Experimental Investigation on the Impact of Drying–Wetting Cycles on the Shrink–Swell Behavior of Clay Loam in Farmland

Soil shrink–swell behavior is a common phenomenon in farmland, which usually alters the process of water and solute migration in soil. In this paper, we report on a phenomenological investigation aimed at exploring the impact of drying–wetting cycles on the shrink–swell behavior of soil in farmland. Samples were prepared using clay loam collected from farmland and subjected to four drying–wetting cycles. The vertical deformation of soil was measured by a vernier caliper, and the horizontal deformation was captured by a digital camera and then calculated via an image processing technique. The results showed that the height, equivalent diameter, volume and shrinkage-swelling potential of the soil decreased with the repeated cycles. Irreversible deformation (shrinkage accumulation) was observed during cycles, suggesting that soil cracks might form owing to previous drying rather than current drying. The vertical shrinkage process consisted of two stages: a declining stage and a residual stage, while the horizontal shrinkage process had one more stage, a constant stage at the initial time of drying. The VG-Peng model fit the soil shrinkage curves very well, and all shrinkage curves had four complete shrinkage zones. Drying–wetting cycles had a substantial impact on the soil shrinkage curves, causing significant changes in the distribution of void ratio and moisture ratio in the four zones. However, the impact weakened as the number of cycles increased because the soil structure became more stable. Vertical shrinkage dominated soil deformation at the early stage of drying owing to the effect of gravity, while nearly isotropic shrinkage occurred after entering residual shrinkage. Our study revealed the irreversible deformation and deformation anisotropy of clay loam collected from farmland during drying–wetting cycles and analyzed the shrink–swell behavior during cycles from both macroscopic and microscopic points of view. The results are expected to improve the understanding of the shrink–swell behavior of clay loam and the development of soil desiccation cracks, which will be benefit research on water and solute migration in farmland.

Unified Elastic Modulus Characteristic Curve Equation for Variably Saturated Soils

A soil’s elastic modulus is a fundamental property defining the soil’s reversible stress-strain relation under mechanical and environmental loadings. It has been observed that a soil’s elastic modulus can increase up to several orders of magnitude from fully saturated to dry conditions due to two distinct soil water retention mechanisms: adsorption and capillarity. Adsorption affects interparticle stress through van der Waals and electrostatic attraction and interparticle friction coefficient through water film retained by soil sorptive potential. Capillarity governs interparticle stress through capillary pressure and surface tension. The onset and scaling laws of the two mechanisms depend on the soil properties of specific surface area, pore-size distribution, cation exchange capacity, and soil mineralogy. These mechanisms are unified by a proposed elastic modulus characteristic curve (EMCC) equation. It is demonstrated that the proposed EMCC equation can well describe the moisture-dependent elastic modulus of a wide array of soils. Further, an interrelation among the EMCC equation, suction stress and soil shrinkage curves is established, which can greatly facilitate predicting suction stress from soil shrinkage curves and vice versa, further validating the EMCC equation in capturing soil’s hydromechanical behavior. The practical importance of the EMCC equation is demonstrated through prediction of ground heave of various soils due to a hypothetical flooding event.

Long‐term effect of sugarcane residue management and chemical fertilization on soil physical properties in South Africa

AbstractSugarcane (Saccharum officinarum L.), an intensive, long‐term, monoculture, economical crop in South Africa, is known to degrade soil characteristics. Soil structure, a key indicator of soil health and biomass production potential, is manageable by agricultural practices. This study aims to evaluate the effect of crop residue management practices (mulching, burning with residues scattered or removed) and mineral fertilization (with or without) on soil structure by analyzing soil shrinkage curves (SSCs) and other soil physical and chemical properties in a long‐term sugarcane trial established in 1939. The SSC provides descriptive structural soil data by differentiating and characterizing two pore systems (plasma and structural pores). By analyzing the SSC of 24 plots (four replicates each treatment), residue management and fertilization practices were found to have statistically and physically significant effects on hydrostructural variables. Partial redundancy analysis showed that residue management practices had a slightly higher effect (19% of total variance) on hydrostructural variables compared with fertilization (12%). The main hydrostructural variables representing the management effect were total soil shrinkage, specific volume, and swelling capacity of the plasma, which were higher in mulched and/or unfertilized plots, indicating that soil was less compact, and shrinkage was more intense, including at the plasma level. The stronger structural dynamics and aggregate stability of the soil were explained by the behavior of the primary aggregates (peds), which were more porous and reactive during the drying process. This study highlights the importance of mulching and limited fertilization to maintain soil structure in the long term while still ensuring yield production.

A Unified Approach for Establishing Soil Water Retention and Volume Change Behavior of Soft Soils

Abstract The assumption of treating the specimen volume as constant while experimentally determining the soil water retention curve (SWRC) of soils is valid only for nonplastic, granular soils. Fine-grained soils usually undergo significant volume change during dewatering and densification, and therefore such an assumption is misleading, even falsifying. The need for developing an easy-to-use lab-scale technique that can enable continuous monitoring of the evolutions in volume, suction, and moisture content of a progressively drying soft soil specimen is evident in the field of characterizing unsaturated soils. Such a method is relevant to establishing SWRC and soil shrinkage curve (SSC) of soft soils that exhibit an appreciable degree of deformation upon subjection to dewatering. To this end, a simple yet improvised method based on the balloon technique incorporating a commercially available high-capacity polymer tensiometer has been proposed to establish SWRC-SSC of soft soils. A comparison between the SWRC and SSC obtained through the proposed method and the conventional methods demonstrated a satisfactory degree of agreement. Densification of the materials realized under the influence of mechanical and hydraulic stresses has been discussed through a comparative analysis between the results from the proposed method and one-dimensional odometer test. For soft soils, the proposed method is particularly appropriate for establishing SWRC in terms of volumetric moisture content and degree of saturation through just a single test.

Review of methods for predicting soil volume change induced by shrinkage

The shrinkage of soil induced by cyclic moisture variation from the post-compaction state needs to be addressed for understanding its long-term performance. The soil shrinkage curve is modeled to characterize the loss of moisture and the associated soil volume change from the initially saturated state to zero volume change phase. The volume change associated with gradual loss of moisture provides insight into the pore volume change, thus necessitating an accurate determination of soil volume. In this article, a detailed review of various measurement methods practiced to quantify the volume change of soil during the desiccation process in the laboratory is discussed. The procedure outlines, advantages, limitations, and the implication of results are discussed elaborately to understand their implications on shrinkage curve characterization. The absolute error of volume measurement by non-contact measurement method can be as low as 0.3% compared with direct measurement procedures. The study highlights the necessity to quantify the anisotropy in volumetric shrinkage and the advantage of using non-contact measurement methods. In particular, this review on the current state-of-the-art practices emphasizes digital image analysis as a cost-effective and reliable approach to quantify the shrinkage of fine grained soils, especially highly expansive clay.

Measurement of Suction Stress and Soil Deformation at High Suction Range

Abstract Suction stress is the effective stress independent of mechanical boundary conditions but is due to water content variation. It occurs on or near particle contacts and does not directly transfer through the soil skeleton and hence can only be and has been measured indirectly and deduced from soil’s strength or deformation. In this work, a new technology to measure the soil-water retention curve, soil shrinkage curve, and suction stress characteristic curve in a high suction environment is established. A humidity-controlled device to measure suction stress was developed based on a previously established drying cake method. Nitrogen gas and molecular sieves were introduced as desiccant in addition to saturated salt solutions to generate an extreme dry environment up to 850 MPa of matric suction for the first time. A focus on the effect of adsorptive soil-water interaction on hydromechanical properties of expansive soils provides enriched information on elastic modulus variation, soil deformation evolution, and matric suction development of soil in very low water contents, making the suction stress measurement possible for matric suction as high as 850 MPa.

Evaluating soil physical quality indicators of a Vertisol as affected by different tillage practices under wheat-maize system in the North China Plain

Soil physical quality (SPQ) is an important parameter for crop growth. Tillage management is widely recognized to affect SPQ remarkably, but such an effect is complicated in Vertisols by shrinking and swelling soil structure. The objectives of this study were to (i) investigate how tillage practices affected SPQ as indicated by the S index, least limiting water range (LLWR) and water stress percentage (WSP); and (ii) determine the relationship between these SPQ indicators and crop yield. A 4-year field experiment, which was conducted in a Vertisol under wheat-maize rotation system in the North China Plain, consisted of four tillage treatments: no tillage (NT), rotary tillage (RT), subsoiling (SS), and deep ploughing (DP). Soil water retention curve (SWRC), soil shrinkage curve (SSC), penetration resistance (PR), and bulk density (BD) of the 0−10 and 10−20 cm layer were measured during wheat and maize seasons, and soil water content was continuously monitored in situ. The S index, LLWR and WSP were determined. Our results showed that SSCs were parallel to each other among four tillage treatments, indicating that tillage did not impact shrinkage capacity (P > 0.05). Relative to NT and RT treatments, the SS and DP treatments improved soil physical quality (higher S index and larger LLWR), particularly in the 10−20 cm layer. The S index presented a poor relation with wheat (P > 0.05) and maize yields (P > 0.05), while LLWR had a significant correlation with wheat yield (P < 0.05) but not with maize yield (P > 0.05). A new proposed SPQ indicator, WSP, is defined as the percentage of the period when the soil water content is above the field water capacity (waterlogging stress percentage, WLP) or below the wilting point (drought stress percentage, DSP) to the entire crop season period. The WLP presented a significantly negative relation with maize yield (P < 0.01) but not with wheat yield (P > 0.05), whereas the DSP had no relation with wheat and maize yield (P > 0.05). Moreover, the WSP was observed to be independent of the volume change in the Vertisol. Our results demonstrate that LLWR and WLP can be regarded as suitable indicators for evaluating SPQ in wheat and maize seasons, respectively, but the latter is more conveniently applied in a Vertisol.

Determination of Soil-Shrinkage Curve Using Transient Water Evaporation Method

Abstract Soil-shrinkage curve (SSC) is an intrinsic constitutive relationship characterizing soil deformation due to variation of water content under drying. The determination of SSC has been chall...

Experimental investigations of soil shrinkage characteristics and their effects on the soil water characteristic curve

The magnitude of the volume change in response to changes in the water content is usually described by the soil-shrinkage characteristic curve (SSCC). The void ratio of soil is affected by its shrinkage behavior, and the soil water characteristic curve (SWCC) will be affected. In this paper, a new test platform is introduced to measure the soil shrinkage behavior during the drying process of silicon micropowder (SMP), Guangxi Guiping clay (GGC) and kaolin. The soil water characteristic curves of these tested soils were measured without and with considering volume change during soil shrinking. The results show that after drying ended, the volume shrinkage values of the soil samples were 0.31%, 20.1% and 31.4%, while the corresponding initial void ratios were 0.67, 1.03, and 1.04, respectively. The soil shrinkage curve with decreasing water content could be divided into three stages: normal shrinkage, residual shrinkage and zero shrinkage. In addition, the void ratio after soil shrinkage had a considerable influence on the SWCC. • This paper proposed a new method for measuring the shrinkage and deformation of soil samples. • The soil water characteristic curves are measured without and with considering volume change during soil shrinking. • The void ratio after soil shrinkage had a considerable influence on the SWCC.

Impact of Dairy Wastewater Irrigation and Manure Application on Soil Structural and Water-Holding Properties

HighlightsQuantitative evaluation was performed of dairy waste on soil water-holding capacity.Considering the soil variability on a farm is significant for management practices.Soil aggregate structure plays a pivotal role in studying the impact of waste reuse.Abstract. The livestock sector contributes about 40% of global agricultural output and uses over 30% of total feed-crop land. The sector’s continuing growth has led to increased technology and larger-scale, commercialized agriculture, and it correlates to growth in by-products and waste, which can compromise the environment and human health. Although organic manure is an excellent soil fertilizer whose nutrient content increases crop yield, untreated and/or overapplied manure pollutes local water resources and can alter soil aggregate structure, potentially affecting soil health and available water. Proper livestock waste management is essential for sustainable food production. Waste reuse strategies exist, with goals such as minimizing freshwater consumption, improving food production, and contributing to energy production, However, each strategy has tradeoffs in environmental, energy, or monetary costs. This study provides a quantitative approach to evaluating waste impact on soil health and helps to better manage irrigation practices and water supply gaps in arid and semi-arid areas by better understanding how management practices affect physical soil health. The TypoSoil apparatus was used to measure and analyze the hydrostructural parameters (water-holding capacity and soil structure) of fine sandy loam (A horizon) and sandy clay (B horizon). Soils from the Texas A&amp;amp;M AgriLife Research Dairy (Stephenville, Texas) were collected and compared with control (untouched) soils. Waste (manure, bedding materials, wash water) was separated into liquid (passed through a natural lagoon treatment process) and solid components (applied as fertilizer). Approximately half the wastewater was reused as wash water, the remainder for irrigation. Although the soil varied substantially between sample locations, a statistically significant difference existed between the control and manure/wastewater applications in both the A and B horizons. Both applications improved plant-available water (AW) in the A horizon (40% and 30%, respectively) but deteriorated AW in the B horizon (25% and 30%). Thus, dairy farm waste is a viable source for agricultural use. Keywords: Available water capacity, Pedostructure, Soil health, Soil shrinkage curve, Soil water characteristic curve.

On the characterization of the shrinkage behavior and soil-water retention curves of four soils using centrifugation and their relation to the soil structure

In this study, a consistent centrifuge procedure was applied to four soils. The height shrinkage, bulk density increase, soil shrinkage curve (SSC), and soil-water retention curve (SWRC) of the soils were analyzed. Scanning electron microscopy (SEM) tests and image processing techniques were adopted to qualitatively and quantitatively investigate the microstructure of the soils with different bulk densities. The results showed that under a matric suction ranging from 0 to 2000 kPa, the bulk density increased from an initial value of 1.30 g/cm3 to 1.60, 1.72, 1.61, and 1.57 g/cm3 for the soils retrieved from Chanhe, Qingyang, Yan’an, and Lvliang, respectively, resulting in corrected SWRCs considering soil shrinkage that was higher than the uncorrected SWRCs, consistent with previously published work. However, this difference was effectively reduced by retesting the soil samples. A reduction in water volume resulted in the same reduction in the bulk soil volume in the normal shrinkage state, while a shrinkage rate higher than one was found with increasing soil drying. More hydraulically active and connected macropores were detected in the low-density soil. The maximum pore diameter, total pore area ratio (PAR), pore size, and number distribution considerably changed with increasing density. The captured microstructural information is beneficial for the interpretation of the shrinkage behavior and hydraulic properties of soil.

Microstructural evolution of expansive clay during drying–wetting cycle

This paper presents a comprehensive investigation on the microstructural evolutions of expansive clay during a drying–wetting cycle, including pore size distribution (PSD) via mercury intrusion porosimetry and water distribution via nuclear magnetic resonance (NMR). The soil water characteristic curves at different soil densities and soil shrinkage curve are also obtained, and a threshold suction can be identified to distinguish the adsorptive and capillary regimes of pore water. Combined with the water distribution obtained by the NMR technique, the evolutions of the adsorptive water and capillary water during drying–wetting cycle were addressed. The measured PSD curves of the expansive soils at different suctions showed two distinct peaks, corresponding to micropores and macropores, respectively. Both variations of macropores and micropores are irreversible during the wetting–drying cycle, which partly explain the adsorptive water content decreasing when the suction is small.

Erratum for “Correlation between Soil-Shrinkage Curve and Water-Retention Characteristics” by Ning Lu and Yi Dong

Erratum for “Correlation between Soil-Shrinkage Curve and Water-Retention Characteristics” by Ning Lu and Yi Dong

Discussion of “Generalized Equation for Soil Shrinkage Curve” by Pan Chen and Ning Lu

Discussion of “Generalized Equation for Soil Shrinkage Curve” by Pan Chen and Ning Lu