Three-dimensional Swelling Research Articles

Dynamic Mechanical Performance of Sulfate-Bearing Soils Stabilized by Magnesia-Ground Granulated Blast Furnace Slag

Sulfate soils often caused foundation settlement, uneven deformation, and ground cracking. The distribution of sulfate-bearing soil is extensive, and effective stabilization of sulfate-bearing soil could potentially exert a profound influence on environmental protection. Ground granulated blast furnace slag (GGBS)–magnesia (MgO) can be an effective solution to stabilize sulfate soils. Dynamic cyclic loading can be used to simulate moving vehicles applied on subgrade soils, but studies on the dynamic mechanical properties of sulfate-bearing soil under cyclic loading are limited. In this study, GGBS-MgO was used to treat Ca-sulfate soil and Mg-sulfate soil. The swelling of the specimens was analyzed by a three-dimensional swelling test, and the change in compressive strength of the specimens after immersion was analyzed by an unconfined test. The dynamic elastic properties and energy dissipation of GGBS-MgO-stabilized sulfate soils were evaluated using a fatigue test, and the mineralogy and microstructure of the stabilized soils were investigated by X-ray diffraction and scanning electron microscopy. The results showed that the maximum swelling percentage of stabilized Ca-sulfate soil was achieved when the GGBS:MgO ratio was 6:4, resulting in an expansion rate of 14.211%. In contrast, stabilized Mg-sulfate soil exhibited maximum swelling at GGBS:MgO = 9:1, with a swelling percentage of 5.127%. As the GGBS:MgO ratio decreased, the dynamic elastic modulus of stabilized Ca-sulfate soil diminished from 2.8 MPa to 2.69 MPa, and energy dissipation reduced from 0.02 MJ/m3 to 0.019 MJ/m3. Conversely, the dynamic elastic modulus of stabilized Mg-sulfate soil escalated from 2.16 MPa to 6.12 MPa, while energy dissipation decreased from 0.023 MJ/m3 to 0.004 MJ/m3. After soaking, the dynamic elastic modulus of Ca-sulfate soil peaked (4.01 MPa) and energy dissipation was at its lowest (0.012 MJ/m3) at GGBS:MgO = 9:1. However, stabilized Mg-sulfate soil exhibited superior performance at GGBS:MgO = 6:4, with a dynamic elastic modulus of 0.74 MPa and energy dissipation of 0.05 MJ/m3. CSH increased significantly in the Ca-sulfate soil treated with GGBS-MgO. The generation of ettringite increased with the decrease in the GGBS-MgO ratio after immersion. MSH and less CSH were formed in GGBS-MgO-stabilized Mg-sulfate soil compared to Ca-sulfate soils. In summary, the results of this study provide some references for the improvement and application of sulfate soil in the field of road subgrade.

Unconstrained dynamic gel swelling generates transient surface deformations.

Polymer gels are comprised of a three-dimensional, cross-linked network that can typically withstand the mechanical deformation associated with both swelling and de-swelling. Thus, gels can be designed with smart behaviors that require both stress generation and dissipation, making them well-suited to many applications including membrane technology, water capture devices, and drug delivery systems. In contrast to the fully swelled equilibrium state, limited research characterizes the unsteady-state swelling regime prior to equilibrium. It is in this regime where unique surface deformations can occur. Here we show how internal network constraints and external diffusive pressure can be leveraged to manipulate swelling kinetics and surface deformations in poly(ethylene glycol) gels during unconstrained, three-dimensional swelling. We find that increasing cross-linker molecular weight and swelling in ethanol, as opposed to water, are both effective routes to increase the time it takes to reach equilibrium but do so through different mechanisms. Networks with fewer internal constraints, manipulated via cross-linker chain-length, imbibe more solvent over a longer time. In contrast, swelling in ethanol reduces the amount of solvent imbibed by the network while increasing the time to reach equilibrium. Measurements of surface patterns during swelling establishes that an immediate, fast relaxation at the surface occurs during the first five minutes of swelling. However, the density and persistence of these features varies with solvent quality. These results establish a framework for how soft materials undergo dynamic deformation. Engineering transient surface properties while mitigating unwanted instabilities opens the door for emerging technologies such as smart anti-fouling and sensors.

Structure, composition and anisotropic swelling of the bovine acetabular labrum

The fibro-cartilaginous labrum surrounds the acetabular rim and is important for hip joint stability and sealing. Sealing may be enhanced by swelling pressure within the normal labrum. Swelling of the degenerated or torn labrum might occur and potentially contribute to the development of osteoarthritis, through altered load transmission. This study aimed to characterize the three-dimensional swelling behaviour, the collagen fiber orientation and spatial proteoglycan distribution of the bovine acetabular labrum. Specimens were harvested from bovine donors (192–652 days, male, n = 6 donors). Structure was analyzed by scanning electron microscopy, histology, and dimethylmethylene blue assay. Specimen dimensions were measured before and after incubation in phosphate buffered saline to assess the swelling. Results showed that the articulating surface is composed of a collagen mesh network. Collagen fiber bundles showed a low degree of alignment close to the surface and were circumferentially aligned in the deep tissue. Proteoglycans were identified clustered between the collagen bundles. Glycosaminoglycan content was 10 x lower than that of cartilage (23.1 ± 6.4 compared to 299.5 ± 19.1 μg/mg dry weight) with minor regional differences. Specimens swelled significantly more in the orthogonal direction (swelling ratio 124.7 ± 10.2%) compared to the swelling parallel to the articulating surface (108.8 ± 6.1% and 102.8 ± 4.1%). In the deep tissue, swelling was also restricted in the main collagen fiber bundle direction (circumferentially), with a swelling ratio of 109.5 ± 4.0% in the main fiber bundle direction compared to 126.8 ± 7.3 % and 122.3 ± 5.8% radially. The findings demonstrate that the labrum shows anisotropic swelling properties, which reflect the anisotropy in the tissue structure and inter-fiber localisation of proteoglycans.

Stabilization of High Sulfate-Saline Soil with Lime, Ground Granulated Blast Furnace Slag (GGBFS), and Basic Oxygen Furnace Slag (BOFS)

Saline soil is an inferior and special material consisting of fine soil particles and possesses poor engineering properties. The swelling, salt heaving, and corrosive behaviors of this soil render it unsuitable for pavement construction due to its deteriorating effects. To use this soil as a subgrade material in the roadway, this soil needs to meet various engineering standard criteria such as deformation, sulfate reduction, strength, and durability for use as subgrade material. Hence, the soil underwent careful stabilization using designed proportions of chemical additives such as lime and slag-based materials. The paper studied the feasibility of using slag-based materials (by-products of the steelmaking process) such as ground granulated blast furnace slag (GGBFS) and basic oxygen furnace slag (BOFS) with lime in stabilizing sulfate-saline soil. On this premise, four designed mixtures, which include saline soil (control), [soil+6% lime], [soil+4% lime+2% (50% GGBFS+50% BOFS)], and [soil+4%lime+2% (70% GGBFS+30% BOFS)] for use to determine their various geotechnical and durability properties. The experimental program for determining these properties included proctor compaction, unconfined compressive strength, three-dimensional (3-D) swelling, and dielectric constant tests. As a result, the laboratory test findings have revealed that adding GGBFS and BOFS to the lime-treated saline soil decreased the maximum dry density, enhanced the strength parameter, and reduced the soil's volumetric swelling and moisture susceptibility.

Experimental study on three-dimensional swelling pressure of compacted GMZ bentonite–sand mixtures

Experimental study on three-dimensional swelling pressure of compacted GMZ bentonite–sand mixtures

Experimental Study on the Relationship between Three-dimensional Stress Attenuation Value and Strain of Remolded Expansive Soil

This paper studies the characteristic of remolded expansive clay in Hefei. A series of three-dimensional swelling tests were conducted for cubic expansive soil of different initial moisture contents and dry density as well as the swelling pressure tests under the control of the vertical strain and the lateral strain. The research results show that: (1) Under the same initial water content, the vertical displacement of the soil sample is released. At this time, the attenuation value of both the horizontal and vertical expansion force of the soil sample increases with the increase of the initial dry density. (2) The horizontal displacement of the soil sample is released. At this time, the attenuation value of the horizontal expansion force of the soil sample increases with the increase of the initial dry density. Moreover, the horizontal displacement of the soil sample is released in the case of the same initial dry density. And the attenuation value of the horizontal expansion force of the soil sample decreases with the increase of the initial water content.

Potential of limestone powder to improve the stabilization of sulfate-contained saline soil

The geotechnical properties of soils differ from area to area, depending on the origin of soil, environmental conditions of a region, and soil treatment processes. As a subgrade material in pavement construction, however, the soil is required to meet specific standards for its engineering properties, such as plasticity, deformability, strength, and durability parameters. For this purpose, soil undergoes a stabilization process, in which it is treated with chemical additives. This paper studies the potential of limestone powder as a stabilizer in combination with cement in the stabilization of sulfate-contained saline soil. For this purpose, silty sand (A-2-4(0) according to AASHTO soil classification system) containing high sulfate and sodium contents was stabilized with 6% and 8% cement by dry weight, 2% and 4% limestone powder at fixed 4% cement content, and 2% limestone powder by dry weight at 6% cement content. Series of tests were performed to determine the improvement of geotechnical properties of these mixtures, such as unconfined compressive strength, Atterberg limits, three-dimensional (3-D) swelling, and dielectric constant. Experimental results show that the addition of limestone powder to the cement-treated saline soil decreases soil plasticity, increases maximum dry density, improves strength parameter, reduces volumetric swelling and moisture susceptibily of soil.

Hydrogel core flexible matrix composite (H-FMC) actuators: theory and preliminary modelling

The underlying theory of a new actuator concept based on hydrogel core flexible matrix composites (H-FMC) is presented. The key principle that underlines the H-FMC actuator operation is that the three-dimensional swelling of a hydrogel is partially constrained in order to improve the amount of useful work done. The partial constraint is applied to the hydrogel by a flexible matrix composite (FMC) that minimizes the hydrogelʼs volume expansion while swelling. This constraint serves to maximize the fixed charge density and resulting osmotic pressure, the driving force behind actuation. In addition, for certain FMC fibre orientations the Poissonʼs ratio of the anisotropic FMC laminate converts previously unused hydrogel swelling in the radial and circumferential directions into useful axial strains. The potential benefit of the H-FMC concept to hydrogel actuator performance is shown through comparison of force–stroke curves and evaluation of improvements in useful actuation work. The model used to achieve this couples chemical and electrical components, represented with the Nernst–Plank and Poisson equations, as well as a linear elastic mechanical material model, encompassing limited geometric nonlinearities. It is found that improvements in useful actuation work in the order of 1500% over bare hydrogel performance are achieved by the H-FMC concept. A parametric study is also undertaken to determine the effect of various FMC design parameters on actuator free strain and blocking stress. A comparison to other actuator concepts is also included.

Shrinkage and swelling of coal induced by desorption and sorption of fluids: Theoretical model and interpretation of a field project

Abstract Geologic sequestration in deep unmineable coal seams and enhanced coalbed methane production is a promising choice, economically and environmentally, to reduce anthropogenic gases such as carbon dioxide in the atmosphere. Unmineable coal seams are typically known to adsorb large amounts of carbon dioxide in comparison to the sizeable amounts of sorbed methane, which raises the potential for large scale sequestration projects. During the process of sequestration, carbon dioxide is injected into the coalbed and desorbed methane is produced. The coal matrix is believed to shrink when a gas is desorbed and swell when a gas is sorbed, sometimes causing profound changes in the cleat porosity and permeability of the coal seam. These changes may have significant impact on the reservoir performance. Therefore, it is necessary to understand the combined influence of swelling and shrinkage, and geomechanical properties including elastic modulus, cleat porosity, and permeability of the reservoir. The present paper deals with the influence of swelling and shrinkage on the reservoir performance, and the geomechanical response of the reservoir system during the process of geologic sequestration of carbon dioxide and enhanced coalbed methane production in an actual field project located in northern New Mexico. A three-dimensional swelling and shrinkage model was developed and implemented into an existing reservoir model to understand the influence of geomechanical parameters, as well as swelling and shrinkage properties, on the reservoir performance. Numerical results obtained from the modified simulator were compared to available measured values from that site and previous studies. Results show that swelling and shrinkage, and the combination of geomechanical and operational parameters, have a significant influence on the performance of the reservoir system.

Modelling of alcohol and water diffusion in fuel cell membranes—Experimental validation by means of in situ Raman spectroscopy

In this work a multi-component transport model has been set up to describe the diffusion driven mass transport of water and methanol in fuel cell membranes. For a membrane in contact with liquid methanol and water on one side and conditioned air on the other, the corresponding differential equations and boundary conditions were derived in a polymer-related coordinate system taking into account the polymers three-dimensional swelling. Phase equilibrium parameters and unknown diffusion coefficients for Nafion ® 117 were obtained by comparing the simulation results to water and methanol concentration profiles measured with confocal Raman spectroscopy. The influence of methanol concentration, temperature and air flow rate was predicted by the model with a maximum relative mean deviation between measurement and simulation of 8.6% for methanol and 3.4% for water.

Ceramic-supported thin PVA pervaporation membranes combining high flux and high selectivity; contradicting the flux-selectivity paradigm

Thin, high flux and highly selective cross-linked poly(vinyl)alcohol waterselective layers have been prepared on top of hollow fibre ceramic supports. The supports consist of an α-Al 2O 3 hollow fibre substrate and an intermediate γ-Al 2O 3 layer, which provides a sufficiently smooth surface for the deposition of ultra-thin PVA layers. Membranes have been characterised by SEM and pervaporation experiments. The thickness of the PVA layer formed on top of the γ-Al 2O 3 intermediate layer is in the order of 0.3–0.8 μm. No significant infiltration of PVA into the intermediate γ-Al 2O 3 layer can be observed. In the dehydration of 1-butanol (80 °C, 5 wt.% water) the membranes exhibit a high water flux (0.8–2.6 kg m −2 h −1), combined with a high separation factor (500–10,000). The values for the flux and separation factor exceed typical values obtained for cross-linked PVA membranes on polymeric supports. In the dehydration of 2-propanol and 1-butanol, a simultaneous increase in both water flux and separation factor is observed with increasing temperature or water concentration. This remarkable behaviour is in contrast to the trade-off generally observed for polymer membranes, i.e., an increase in flux is typically combined with a decrease in separation factor. A possible explanation for this behaviour is a low degree of three-dimensional swelling in the vicinity of the γ-Al 2O 3–PVA interface due to an enhanced structural stability. In the dehydration of ethanol and 1-propanol the traditional trade-off between flux and selectivity was observed.

Three-dimensional swelling of clay lumps

The disposal of large volumes of clay lumps obtained from underground construction activities and seabed dredging is a problem in a highly built-up environment such as Singapore. The use of such clay lumps for reclamation of land is an environment-friendly proposition. The clay lumps, when placed under water, will undergo three-dimensional swelling. Calculation of the degree of swelling is important for making decisions on when to place surcharge, and in what quantity, on top of the fill for closing the inter-lump voids. This paper reports the results of experimental and numerical studies that were carried out to understand the swelling behaviour of clay lumps when placed under water. Experimental results were compared with finite element method results using linear and non-linear elastic models. The study shows that the suction present in the lumps increases initially, before dissipation, suggesting the presence of the Cryer-Mandel effect during three-dimensional swelling. The importance of simulating continuous changes in soil modulus and permeability for realistic simulation of three-dimensional swelling of clay lump is reported. The influence of lateral restraint on the swelling behaviour is also analysed.

Three-dimensional swelling of clay lumps

The disposal of large volumes of clay lumps obtained from underground construction activities and seabed dredging is a problem in a highly built-up environment such as Singapore. The use of such clay lumps for reclamation of land is an environment-friendly proposition. The clay lumps, when placed under water, will undergo three-dimensional swelling. Calculation of the degree of swelling is important for making decisions on when to place surcharge, and in what quantity, on top of the fill for closing the inter-lump voids. This paper reports the results of experimental and numerical studies that were carried out to understand the swelling behaviour of clay lumps when placed under water. Experimental results were compared with finite element method results using linear and non-linear elastic models. The study shows that the suction present in the lumps increases initially, before dissipation, suggesting the presence of the Cryer-Mandel effect during three-dimensional swelling. The importance of simulating continuous changes in soil modulus and permeability for realistic simulation of three-dimensional swelling of clay lump is reported. The influence of lateral restraint on the swelling behaviour is also analysed.

Parameters affecting the determination of transport kinetics data in highly swelling polymers above Tg

Sorption and desorption data for n-hexane–natural rubber and n-hexane–low-density polyethylene were analysed to reveal the cause of the s-shaped sorption curves frequently occurring in highly swollen polymers. The model permitted the influence of solute-concentration-dependent diffusivity, sample geometry, boundary concentrations and swelling-induced mechanical stresses on the transport data to be examined. The calculated solute diffusivity varied by several orders of magnitude, depending on the choice of parameters included in the model. The inclusion of direct mechanical stress relaxation parameters only gave a slight improvement of the fit to the experimental data. The inclusion of a time-dependent surface concentration was the only way to fit the s-shaped sorption curves for both natural rubber and low-density polyethylene. Although isotropic three-dimensional swelling of natural rubber occurred over the whole sorption transient period, this condition was unable to explain the swelling (thickness increase) of low-density polyethylene. In the latter system, a model consisting of two stages had to be adopted: stage I where the swelling was mainly one-dimensional, and stage II which occurred later and was characterized by three-dimensional swelling similar to that occurring in natural rubber. During the transient sorption period, the ratio between natural rubber and low-density polyethylene of the ratio of the thickness to cross-sectional area was close to their bulk modulus ratio, which suggests that it is the bulk modulus rather than the Young's modulus which determines the sorption characteristics of polymers above T g.

Three-dimensional anisotropic swelling model for clay shale —a fabric approach

A three-dimensional model is developed to quantify the anisotropic swelling behaviour of geological materials. The model considers clay mineral particle swelling, fabric anisotropy and induced stress anisotropy as important fundamentals. The double layer theory is used to describe the relationship between the interactive particle stress and the swelling strain. Continuous functions are introduced to represent the fabric density and the particle stress distributions and to permit continuum analyses of three-dimensional swelling problems. The performance of the model has been evaluated against the experimental data obtained from swell tests on a clay soil and two clay shales. It is found that the model provides reasonable predictions on the swelling behaviour of high-density clay shale in which the swelling is dominated by the microstructural particle swelling rather than the macrostructural matrix deformation.

Characterization of moving fronts in cross-linked amylose matrices by image analysis

The purpose of this work was to characterize swelling and solvent concentration gradients in large matrices by image analysis. Tablets prepared by direct compression of cross-linked amylose (CLA), a polymer used for controlled release of drugs, with 10% diltiazem HC1 were studied. Matrices corresponding to 3 different degrees of cross-linking were compared. The technique was simple and precise. It permitted the characterization of the changes occurring at the surface as well as inside the tablets during water sorption. The solvent penetrated all sides of the tablets. Three-dimensional swelling was recorded. Axial swelling was more pronounced than radial swelling for the 3 types of CLA. Augmenting the degree of cross-linking from 6 to 11 significantly increased the degree of swelling and solvent transport kinetics in CLA tablets. The equilibrium swelling state was attained much after the solvent penetration fronts had met.

A triaxial swelling test apparatus

This paper describes a new triaxial swelling test apparatus, and presents some of its applications to testing procedures. The apparatus was developed to simulate in-situ stress state in laboratory specimens, and to determine the three-dimensional swelling characteristics of clay-bearing rocks. The cell is based on the oedometer principle, but places a specimen within its jacket, so that various levels of confining pressure can be applied. Its main parts are: (1) loading platens including porous stones; (2) rubber jacket and its seating cylinder; (3) end caps. The apparatus can be used to determine: (1) axial swelling stress under various confining pressures; (2) axial swelling strain under various confining pressures; (3) axial swelling stress as a function of permitted axial swelling strain under various confining pressures. The first two tests are simple, and give results that are useful in preliminary analyses. Only the third test describes the complete stress-strain behaviour. The complete swelling stress-strain tests were performed for a marl sample, whose results are given in the paper, and for some other samples. A simple mathematical expression is derived for the 'three-dimensional swelling behaviour' of clay-bearing swelling rocks. Its parameters depend on the type and amount of clay minerals, initial water content, and other variables.

Time-dependent deformation behaviour of Queenston shale

New methods for simultaneous measurement of three orthogonal strains in time-dependent deformation under several stress systems are described. Results of an extensive series of tests on oriented specimens of Queenston shale, with known magnitude and direction of in situ stress, are reported, together with tests on other shales from southern Ontario. It is found that over the stress range expected in field problems, the swelling behaviour is orthotropic and highly stress dependent. The application of stress in one principal direction not only suppresses the swelling in that direction but also reduces the swelling in the orthogonal directions. A method for representing this strongly nonlinear behaviour is described. Key words: shales, Queenston shale, time-dependent deformation, stress dependency, three-dimensional swelling.

Sources of bias in the field calibration of a neutron meter

Field calibrations of a neutron moisture meter and a gamma density meter were made on the individual layers of a duplex soil consisting of a metre depth of sand overlying a deep cracking clay. Two sources of bias were encountered in the case of the clay layer: (1) differences in bulk density and composition between sites caused a bias of 20% in the calibration coefficient resulting in an underestimate of change in water content, and (2) non-representivity of the access tubes, due to failure to sample cracks, caused an additional negative bias of up to 30%. The first of these inaccuracies can be avoided by using a better design for the calibration experiment and by correcting neutron count rate for soil density. The second bias due to poor crack sampling can be corrected for on the assumption that only three-dimensional swelling occurs on a field-wide basis.