Modelling coating cohesion effect on soil mechanical stability and permeability of the biopore - matrix interface pore region

2021 ◽  
Author(s):  
Luis Alfredo Pires Barbosa ◽  
Horst H. Gerke
Keyword(s):  
Axial Compression ◽  
Mechanical Stability ◽  
Transport Processes ◽  
Spherical Particles ◽  
External Loading ◽  
Hydraulic Permeability ◽  
Matrix Interface ◽  
Pore Region ◽  
Soil Matrix ◽  
Soil Stiffness

<p>Biopore surface is often characterized by finer particles and increased concentration of polysaccharides from root and earthworm exudates, presenting physico-chemical properties different from those of the soil matrix. Such exudates controls not only the wettability or sorption properties but also the adhesive forces of the surrounding soil particles. Thus, increased mechanical stability may be expected on biopore-matrix interface affecting preferential flow and transport processes, as well.</p> <p>However, it is still unknown (i) to what extent the particle cohesion in the coated region is able to increase the resilience of the biopore to an external loading and (ii) how it affects the permeability of the biopore-matrix pore region.</p> <p>We created a discrete element model (DEM) model of a hollow cylindrical soil sample with a coated biopore in the center (i.e., 1 cm height, 1 cm outer and 0.6 cm inner diameter). The spherical particles in the model presented diameter of 0.13 mm for the coated material and 0.22 mm for the soil matrix. The cohesion among particles in the soil matrix was set to a constant value of 10.9 MPa while the cohesion among particles in the coated region varied between 10.9 and 50.9 MPa. The sample was subjected to axial compression and the force and cracks recorded. The permeability in the radial direction from the biopore to soil matrix was calculated using ImageJ and a 3D stokes solver (FDMMS).</p> <p>The increment in the coating cohesion increased the overall soil stiffness in terms of the Young’s modulus. Before axial compression, the calculated hydraulic permeability for the interface coating and matrix was 182 μm<sup>2</sup>. After compression, although the lower coating cohesion resulted in a larger number of cracks, permeability increased with coating cohesion. This suggests that with increasing soil stiffness, the cracks decrease in number but increase in length (i.e. improved connectivity).</p>

Structural characterization and permeability estimation for soil regions at the interface between biopore coating and soil matrix

2021 ◽  
Author(s):  
Luis Alfredo Pires Barbosa ◽  
Horst H. Gerke
Keyword(s):  
Size Distribution ◽  
Preferential Flow ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Crack Size ◽  
Structural Features ◽  
Coating Material ◽  
Hydraulic Permeability ◽  
Soil Matrix ◽  
Earthworm Burrows

<p>During preferential flow events, soil macropores such as cracks and biopores (decayed root channels and earthworm burrows) may allow water and solutes to bypass the lower permeable soil matrix. The biopore walls are inherently compacted by the locomotion mechanism employed by earthworms and roots. In addition, there are the excretion of biopolymers and the hydrophobicity of mucilage excreted by the roots of plants or mucus by earthworms. This gives to the biopore a coating with physicochemical properties distinct from the soil matrix, such as wettability, sorption and cation exchange capacity. Consequently, changes in the mechanical properties of the material in that region are also expected, ensuring greater mechanical stability.</p><p>However, micro structural features (i.e. crack size distribution) are still poorly explored. The objective is to analyze such features in detail, in order to better understand the effects of the coating material on soil macro mechanical behaviour (i.e. tensile strength) to explain the flow exchange between biopore and the soil matrix.</p><p>Therefore, soil samples were collected from Bt horizons of two Haplic Luvisols located in northern Bohemia (Hnevceves, near Hradec Kralove, Czech Republic; 50°18′47′′ N, 15°43′03′′ E). From these air dried samples, three earthworm burrows were identified and carefully separated from soil matrix.</p><p>The samples were scanned with X-ray microtomography (X-TEk XCT 225, Nikon Metrology), using 100 keV, 120μA and no filter. The reconstruction of three-dimensional images was done with the CT Pro 3D software package (version 3.1) at a spatial resolution of 10μm and 8-bit gray scale resolution. The permeability in each region was calculated along the biopore and perpendicularly to the biopore from matrix to coating using stokes solver.</p><p>The calculated hydraulic permeability for coating and matrix was 55 and 0.4 μm<sup>2</sup> along biopore direction and 11 and 3 μm<sup>2</sup> perpendicularly to the biopore. The results from image analysis show no differences in crack size distribution between the materials, but the number of cracks and connections were superior for the coating material, suggesting that the differences in the pore structure can strongly affect the macropore-matrix mass exchange.</p>

Mechanical Stability of PDMS-Based Micro/Nanotextured Flexible Superhydrophobic Surfaces under External Loading

2019 ◽  
Vol 11 (51) ◽  
pp. 48583-48593 ◽  
Author(s):  
Ning Wang ◽  
Qing Wang ◽  
Shuangshuang Xu ◽  
Xu Zheng
Keyword(s):  
Mechanical Stability ◽  
Superhydrophobic Surfaces ◽  
External Loading

scholarly journals Mechanical Integrity of Conductive Carbon-Black-Filled Aqueous Polymer Binder in Composite Electrode for Lithium-Ion Battery

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1460
Author(s):  
Kehua Peng ◽  
Yaolong He ◽  
Hongjiu Hu ◽  
Shufeng Li ◽  
Bao Tao
Keyword(s):  
Carbon Black ◽  
Composite Electrode ◽  
Mechanical Stability ◽  
Critical Role ◽  
Active Material ◽  
Mechanical Damage ◽  
Lithium Ion ◽  
Spherical Particles ◽  
Inorganic Filler ◽  
Composite Electrodes

The mechanical stability of aqueous binder and conductive composites (BCC) is the basis of the long-term service of composite electrodes in advanced secondary batteries. To evaluate the stress evolution of BCC in composite electrodes during electrochemical operation, we established an electrochemical–mechanical model for multilayer spherical particles that consists of an active material and a solid-electrolyte-interface (SEI)-enclosed BCC. The lithium-diffusion-induced stress distribution was studied in detail by coupling the influence of SEI and the viscoelasticity of inorganic-filler-doped polymeric bonding material. It was found that tensile hoop stress plays a critical role in determining whether a composite electrode is damaged or not—and circumferential cracks may primarily initiate in BCC, rather than in other electrode components. Further, the peak tensile stress of BCC is at the interface with SEI and does not occur at full lithiation due to the relaxation nature of polymer composite. Moreover, mechanical damage would be greatly misled if neglecting the existence of SEI. Finally, the structure integrity of the binder and conductive system can be effectively improved by (1) increasing the carbon black content as much as possible in the context of meeting cell capacity requirements—it is greater than 27% and 50% for sodium alginate and the mixtures of carboxy styrene butadiene latex and sodium carboxymethyl cellulose, respectively, for composite graphite anode; (2) reducing the elastic modulus of SEI to less than that of BCC; (3) decreasing the lithiation rate.

Mechanisms of soil matrix water replenishment in a sub-arctic till soil based on an isotope tracer experiment

2020 ◽  
Author(s):  
Filip Muhic ◽  
Pertti Ala-Aho ◽  
Matthias Sprenger ◽  
Hannu Marttila ◽  
Björn Klöve
Keyword(s):  
Soil Moisture ◽  
Soil Water ◽  
Field Data ◽  
Transport Processes ◽  
Average Intensity ◽  
Data Set ◽  
Soil Matrix ◽  
Water Mixing ◽  
Geophysical Surveys ◽  
Arctic Conditions

<p>Due to changes in the snowmelt timing and the potential shift towards less snowfall and more rainfall, infiltration patterns into the soil will increasingly be altered in a warming climate. Mixing and transport processes of water in the unsaturated topsoil layer regulate the subsurface transport and retention of solutes and contaminants, as well as the distribution of plant available water. Recent advances in soil isotope ecohydrology indicate that in some ecosystems, water in macropores largely bypasses soil matrix and rapidly percolates into the groundwater. Here we combine tracer experiments and geophysical surveys to explore soil water mixing in non-stratified till soil in the Pallas catchment located in sub-arctic conditions in Finnish Lapland. A 5x20 m plot at the Kenttärova hilltop was sprinkled with deuterated water (d<sup>2</sup>H 88‰) for two days (totally 200 mm at average intensity of 6.7 mm/h), until surface water ponding was observed on substantial share of the plot. Soil moisture dynamic were monitored by a network of soil moisture sensors and manual soil probe measurements. Soil water was sampled hourly with suction cup lysimeters at three (5 cm, 30 cm, 60 cm) depths and pan lysimeter at 35 cm depth in two soil profiles on the irrigation plot. Groundwater was sampled hourly, while xylem samples from spruce and birch trees in the plot were collected on each day of the experiment and on a weekly basis during the following month. Ground penetrating radar (GPR) survey and soil coring with window sampler down to 1 m depth were completed four times over the course of the experiment, and additional set of soil cores were taken two weeks after the experiment to inspect how natural precipitation events have infiltrated into the deuterium enriched zone. We investigate the mechanisms of soil matrix water replenishment by answering the following questions: i) Can all soil matrix water be displaced during high volume events and when does newly introduced soil matrix water become available to the plants?; ii) What is the extent of soil water mixing at different depths?; and iii) What is the effect of increased moisture content and groundwater table rise on soil water mixing? Due to paucity of field data sets and inability of most hydrological models to accurately simulate soil freezing and thawing effects, ecohydrologic partitioning has been barely studied in Northern regions with seasonal snow cover. We present a novel field data set that focuses on soil matrix water replenishment in glaciated till soil at sub-arctic conditions. Results support our understanding of ecohydrological processes in northern environments where hydrological cycle is dominated by intense infiltration events as it occurs during snowmelt.</p>

Macropore-matrix mass transfer: reactive solute transport as quantified with Fluorescence imaging

2020 ◽  
Author(s):  
Christoph Haas ◽  
Ruth Ellerbrock ◽  
Horst H. Gerke
Keyword(s):  
Mass Transfer ◽  
Soil Properties ◽  
Fluorescence Imaging ◽  
Mass Exchange ◽  
Soil Structure ◽  
Transport Processes ◽  
Hydraulic Transport ◽  
Soil Matrix ◽  
Adsorption Sites ◽  
Sorption Characteristics

<p>Preferential flow paths in soils play a major role for transport processes of heat, gas, water, and solutes and are important adsorption sites. For mass-exchange processes and water storage in soils, small-scaled soil properties, like the spatial distribution of adsorption sites and their accessibility, and the permeability are crucial. Interfaces between macropores (i.e., earthworm burrows, cracks, and root channels) and the soil matrix control the mass exchange. Water and solute transfer through the interface between bio-pores, aggregate or crack surfaces and the matrix was traced at the scale of small soil blocks (≤45 mm edge length) with Fluorescein (i.e., a reactive, fluorescent dye). The objectives were to visualize and quantify hydraulic transport, and sorption characteristics of earthworm-, root- and shrinkage-induced interfaces. Batch experiments were performed to calibrate the Na-Fluorescein tracer concentration versus fluorescence-intensity relationship and to derive parameters for two kinetic sorption models (i.e., Freundlich vs. Langmuir). Fluorescence imaging in the laboratory of small soil blocks was applied with a self-constructed spraying device, and with the help of the calibration, small-scaled dye-concentration maps were derived. Time- and interface-dependent positions of the wetting fronts in vertical direction were estimated with the help of the cumulative infiltration. Assuming equilibrated conditions between Na-Fluorescein in solution (calculated by multiplying the locale dye-concentration and the local water content) and Na-Fluorescein sorbed to soil, the total mass transfers as a function of macropore-type and spraying time were determined. The results of the mass transfer for water and reactive solutes were characteristic for the soil structure type and depending on the composition of the macropore-matrix interface. Differences were explained by alterations in soil structure and chemical composition of the coatings. Results suggest relations between mass exchange and observable soil properties. This can be helpful for improving the numerical simulation of macropore-matrix mass transfer and inverse simulations of small-scaled hydraulic, transport, and sorption characteristics of macropore walls.</p>

Deposition Fraction of Ellipsoidal Particles in a Fully Developed Laminar Pipe Flow: Application of New Correlations for Hydrodynamic Forces and Torques

2014 ◽  
Author(s):  
Mohammad Mehdi Tavakol ◽  
Omid Abouali ◽  
Mahmood Yaghoubi ◽  
Goodarz Ahmadi
Keyword(s):  
Pipe Flow ◽  
Deposition Efficiency ◽  
Hydrodynamic Forces ◽  
Transport Processes ◽  
Creeping Flow ◽  
Spherical Particles ◽  
Low Reynolds Number Flows ◽  
Ellipsoidal Particles ◽  
Deposition Fraction ◽  
Laminar Pipe Flow

The physics of transport, deposition, detachment and reentrainment re-entrainment of particles suspended in a fluid are of great interests in many practical fluid engineering problems. For spherical particles, analysis of their translational motions is sufficient for a complete description of their transport processes. Prediction of transport and deposition of non-spherical particles, however, is more complicated due to the coupling of particle translational and rotational motions. Most studies related to dispersion of ellipsoidal particles used the traditional creeping flow formulations for hydrodynamic forces and torques. These formulations are valid for very low Reynolds number flows. In this study, dispersion and deposition of ellipsoidal particles in a fully developed laminar pipe flow are analyzed numerically using new correlations for hydrodynamic forces and torques. The deposition efficiency of the ellipsoidal particles in laminar pipe flow are calculated and the results are compared with other theoretical and numerical studies and good agreement is observed.

scholarly journals COMPOSED COEFFICIENT TECHNIQUE FOR MODELLING BARRETTE GROUPS

2019 ◽  
Vol 31 (1) ◽  
Author(s):  
Mahmoud El Gendy ◽  
Hassan Ibrahim ◽  
Ibrahim El Arabi
Keyword(s):  
Finite Element ◽  
Soil Structure ◽  
Linear Equations ◽  
Large Section ◽  
Element Mesh ◽  
Soil Matrix ◽  
Soil Stiffness ◽  
Real Practice ◽  
Surrounding Soil ◽  
Coefficient Technique

Most of soil structure interaction methods for analyzing large-section supports such as barrette foundation modeling and the surrounding soil are using 3D finite element (FE) models. In which, the model leads to a large finite element mesh, and consequently a large system of linear equations to be solved. In this paper, Composed Coefficient Technique (CCT) is adapted for analyzing barrette group. The technique considers the 3D full interactions between barrettes and the surrounding soil. Due to the high rigidity of the barrettes relative to the surrounding soil, a uniform settlement for the barrettes can be considered. This is done to compose the stiffness coefficients of the soil matrix into composed coefficients, which consequently leads to a significant reduction in the soil stiffness matrix. An application for analyzing barrette group by CCT technique is carried out on a real subsoil. The application presents guidelines and diagrams for barrette group that may be used in real practice.

LITHIUM-ORTHOSILICATE SPHERICAL PARTICLES WITH HIGH DENSITY AND MECHANICAL STABILITY

1991 ◽  
pp. 822-826
Author(s):  
G. Schumacher ◽  
M. Dalle-Donne ◽  
R. Huber ◽  
J. Lebkücher ◽  
I. Schub
Keyword(s):  
Mechanical Stability ◽  
High Density ◽  
Spherical Particles ◽  
Lithium Orthosilicate

scholarly journals Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study

2016 ◽  
Vol 13 (119) ◽  
pp. 20160234 ◽  
Author(s):  
K. Y. Chooi ◽  
A. Comerford ◽  
S. J. Sherwin ◽  
P. D. Weinberg
Keyword(s):  
Hydraulic Resistance ◽  
Arterial Wall ◽  
Ex Vivo ◽  
Water Flux ◽  
Applied Pressure ◽  
Volumetric Strain ◽  
Transport Processes ◽  
Constitutive Law ◽  
Hydraulic Permeability ◽  
The Media

The hydraulic resistances of the intima and media determine water flux and the advection of macromolecules into and across the arterial wall. Despite several experimental and computational studies, these transport processes and their dependence on transmural pressure remain incompletely understood. Here, we use a combination of experimental and computational methods to ascertain how the hydraulic permeability of the rat abdominal aorta depends on these two layers and how it is affected by structural rearrangement of the media under pressure. Ex vivo experiments determined the conductance of the whole wall, the thickness of the media and the geometry of medial smooth muscle cells (SMCs) and extracellular matrix (ECM). Numerical methods were used to compute water flux through the media. Intimal values were obtained by subtraction. A mechanism was identified that modulates pressure-induced changes in medial transport properties: compaction of the ECM leading to spatial reorganization of SMCs. This is summarized in an empirical constitutive law for permeability and volumetric strain. It led to the physiologically interesting observation that, as a consequence of the changes in medial microstructure, the relative contributions of the intima and media to the hydraulic resistance of the wall depend on the applied pressure; medial resistance dominated at pressures above approximately 93 mmHg in this vessel.

Sign in / Sign up

Export Citation Format

Share Document