Coarse-grained Material Research Articles

Soft Magnetic Properties of Ultra-Strong and Nanocrystalline Pearlitic Wires.

The paper describes the capability of magnetic softening of a coarse-grained bulk material by a severe deformation technique. Connecting the microstructure with magnetic properties, the coercive field decreases dramatically for grains smaller than the magnetic exchange length. This makes the investigation of soft magnetic properties of severely drawn pearlitic wires very interesting. With the help of the starting two-phase microstructure, it is possible to substantially refine the material, which allows the investigation of magnetic properties for nanocrystalline bulk material. Compared to the coarse-grained initial, pearlitic state, the coercivities of the highly deformed wires decrease while the saturation magnetization values increase—even beyond the value expectable from the individual constituents. The lowest coercivity in the drawn state is found to be 520 A m−1 for a wire of 24-µm thickness and an annealing treatment has a further positive effect on it. The decreasing coercivity is discussed in the framework of two opposing models: grain refinement on the one hand and dissolution of cementite on the other hand. Auxiliary measurements give a clear indication for the latter model, delivering a sufficient description of the observed evolution of magnetic properties.

The influence of gravity on granular impacts

Context. Impacts on small-body surfaces can occur naturally during cratering events or even strategically during carefully planned impact experiments, sampling maneuvers, and landing attempts. A proper interpretation of impact dynamics allows for a better understanding of the physical properties and the dynamical process of their regolith-covered surfaces and their general evolution. Aims. This work aims to first validate low-velocity, low-gravity impact simulations against experimental results, and then to discuss the observed collision behaviors in terms of a popular phenomenological collision model and a commonly referenced scaling relationship. Methods. We performed simulations using the soft-sphere discrete element method and two different codes, Chrono and pkdgrav. The simulations consist of a 10-cm-diameter spherical projectile impacting a bed of approximately 1-cm-diameter glass beads at collision velocities up to 1 m s−1. The impact simulations and experiments were conducted under terrestrial and low-gravity conditions, and the experimental results were used to calibrate the simulation parameters. Results. Both Chrono and pkdgrav succeed in replicating the terrestrial gravity impact experiments with high and comparable computational performance, allowing us to simulate impacts in other gravity conditions with confidence. Low-gravity impact simulations with Chrono show that the penetration depth and collision duration both increase when the gravity level decreases. However, the presented collision model and scaling relationship fail to describe the projectile’s behavior over the full range of impact cases. Conclusions. The impact simulations reveal that the penetration depth is a more reliable metric than the peak acceleration for assessing collision behavior in a coarse-grained material. This observation is important to consider when analyzing lander-regolith interactions using the accelerometer data from small-body missions. The objective of future work will be to determine the correct form and applicability of the cited collision models for different impact velocity and gravity regimes.

Understanding the Radiation Resistance Mechanisms of Nanocrystalline Metals from Atomistic Simulation

Metallic materials produce various structural defects in the radiation environment, resulting in serious degradation of material properties. An important way to improve the radiation-resistant ability of materials is to give the microstructure of materials a self-healing ability, to eliminate the structural defects. The research and development of new radiation-resistant materials with excellent self-healing ability, based on defects control, is one of the hot topics in materials science. Compared with conventional coarse-grained materials, nanocrystalline metals with a high density of grain boundary (GB) show a higher ability to resist radiation damage. However, the mechanism of GB’s absorption of structural defects under radiation is still unclear, and how to take advantage of the GB properties to improve the radiation resistance of metallic materials remains to be further investigated. In recent decades, atomistic simulation has been widely used to study the radiation responses of different metals and their underlying mechanisms. This paper briefly reviews the progress in studying radiation resistance mechanisms of nanocrystalline metals by employing computational simulation at the atomic scale.

Experimental Study on the Compaction Characteristics and Evaluation Method of Coarse-Grained Materials for Subgrade.

Coarse-grained materials are widely used in high-speed railway construction, and it is of great significance to research its compaction characteristics due to the high quality control requirements. In this regard, a field compaction experiment was conducted at a subgrade near Bazhou Station of Beijing-Xiong’an Intercity Railway. The test results of the compaction effect were presented in this study at first. The roller-integrated compaction measurements (i.e., compaction meter value, CMV) were compared with several traditional in-situ tests (i.e., plate load test, light falling weight deflectometer test, and shear wave velocity test). Then the stability of CMV was evaluated by the proposed δ criterion. The spatial uniformity of compaction was further investigated. Based on the analysis, the target value of CMV was preliminarily determined. It showed that Evd was more variable than CMV. The results convincingly indicated that the compaction parameters increased with the increasing number of roller passes at first. A further increase in compaction effort could result in the decompaction of material when the compaction number up to a certain value. The stability analysis method proposed in this study showed its potency of quantifying the percentage of areas with acceptable compaction. The geostatistical analysis could reflect the spatial uniformity of compaction. Overall, the conducted study could provide a useful reference for geo-material compaction control in the transportation engineering.

Incorporation of coarse-grained dredged material into marsh and shoreline restoration projects in coastal New Jersey

Millions of cubic yards of sediment are dredged every year in coastal New Jersey for the operation and maintenance of an extensive marine transportation system stretching from the New Jersey Harbor south along the Atlantic Coast from Sandy Hook to Cape May and north up the Delaware River. Dredged material from these public and private projects has been managed using a variety of placement approaches and technologies, from open-water disposal to landfilling to construction materials. For the past several decades, the State of New Jersey has advocated for and implemented a policy of beneficial use of dredged material rather than its disposal. The New Jersey Department of Transportation’s Office of Maritime Resources (NJDOT/OMR) is the lead state agency for research and implementation of beneficial use statewide. NJDOT/ OMR is also responsible for the recovery of the 200-mile network of shallow-draft navigation channels along the Atlantic coast of New Jersey that was damaged by a series of severe coastal storms, most notably Superstorm Sandy in 2012. For the past decade, considerable effort has been made to develop methods that use clean dredged material from the Atlantic region to rebuild and improve coastal features such as marshes, dunes, and beaches, thereby retaining the sediment in the ecosystem. Although there have been a number of successful beneficial use projects, concerns remain about the long-term sustainability of the program due to high cost, timelines, scalability, habitat sensitivity, resiliency, aesthetics, and other factors. This paper explores some of these issues and proposes solutions. It focuses on the use of available coarse-grained material as a way to provide resiliency to these restored features while increasing scale and efficiency, protecting aesthetics, and providing increased habitat value.

Microstructural aspects of new grade ODS alloy consolidated by rotary swaging

In the present paper, the authors have investigated the microstructural aspects of recrystallization of new ODS alloy (Fe-14Cr-10Al-4Y2O3) consolidated by hot rotary swaging. Microstructural characterization of samples was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). Insight of mechanical properties was performed by Vickers hardness testing and measurement of Young's modulus. A thorough analysis of microstructure concerning grains, oxide particles and dislocations was performed for two states of the material, i.e. in the as-received state after rotary swaging exhibiting the ultra-fine-grained microstructure and in the state after annealing provoking the desirable coarse-grained structure. Different conditions of rotary swaging followed by the same annealing conditions induced different structures, either coarse-grained or bimodal when secondary recrystallization did not happen in the entire sample's volume. The hardness measurements revealed no significant difference between the coarse-grained and the bimodal microstructures, however, the coarse-grained material exhibited systematically higher values of the temperature-dependent Young's modulus in comparison with the bimodal counterpart. Detailed microscopic analysis of the material helped to clarify and discuss the measured properties of the newly developed ODS alloy.

Flow characteristics and microstructural evolution in pulsed current assisted micro-scaled compression of stainless steel sheet

Electrically assisted (EA) microforming has pervasive benefits for the fabrication of high-performance microproducts. In this research, the coupled effect between the microstructural size effect and pulsed current on the flow characteristics of 304 stainless steel sheets along thickness direction was explored by using EA micro-compression tests. The results revealed that the strain hardening rate and the deformation stress of 304 stainless steel decreases during the EA deformation, especially when the current density exceeds 57.16 A/mm2. Besides, the effect of grain size on the micro-scaled compression is gradually weakened with the augment of current density and plastic strain. The electron backscatter diffraction (EBSD) results showed in the perspective of microstructure that the decrease of flow stress and strain hardening rate with the rise of pulsed current density is related to the reduction of dislocation density and texture strength due to the dynamic recrystallization during EA deformation. The pulsed current suppresses the grain refinement of fine-grained material and promotes that of coarse-grained material, and the recrystallization rate of EA deformation increases with the decrease of initial grain size. In addition, the recrystallization texture induced by the pulsed current can promote grain deflection and weakens the effect of twins in coarse-grained material. That can explain the reason for the weakening of the grain size effect. The findings in the research have important guiding significance for understanding the coupled mechanism of electroplastic and grain size effect on the flow characteristics of difficult-to-deform material, and further promoting the application of EA micro-rolling of high-strength materials.

Environmental drivers of taxonomic and phylogenetic diversity patterns of plant communities in semi-arid steppe rangelands of North Africa

Since phytoecological and biodiversity studies deepen our understanding on ecosystem functioning and habitat health status of rangelands, this study analyzed the composition and plant taxonomic and phylogenetic diversity of semi-arid steppe vegetation communities in rangelands of northeastern Algeria. Based on 80 floristic samples, vegetation was analyzed using various species diversity parameters (incidence- and abundance-based diversity and similarity indices, rarefaction and extrapolation estimations). Sampling totaled 75,197 plant individuals that were classified into 63 species, 55 genera and 21 families, with predominance of Asteraceae (33.3%) and Fabaceae (14.3%) species. Rarefaction and extrapolation curves applied for the whole steppe vegetation showed that the expected species richness was stable and no rare species could be found when increasing the sample size. Generalized linear models showed that the variation of plant diversity parameters (alpha-biodiversity) was significant among the phytoecological groups individualized. The multiple factor analysis demonstrated that inter-relationships between the phytoecological groups result from characteristics of soil surface, vegetation indicators, and dominant plant species that influenced plant diversity indices. The qualitative and quantitative analysis of similarity (beta-biodiversity) revealed high resemblances (>50%) between these groups, indicating a spatial homogenization of plant communities, which are dominated by annual species. The variation of phylogenetic diversity, estimated using taxonomic structures (i.e. genus/species and family/species ratios) was related to local environmental conditions. Phylogenetic diversity increased with the increase in total vegetation cover and the average height of Halfa grass (Stipa tenacissima), but it was negatively correlated with land degradation indicators such as sand deposit sheets, bedrock outcrop, coarse-grained materials, and plant necromass or vegetation litter). This study demonstrated that despite the recorded plant diversity, the quality of rangelands in the study area was of a therophytic character (substantial level of annuals), indicating a state of land and vegetation degradation in rangelands of northeastern Algeria.

A Simple Water Retention Model Based on Grain Size Distribution

The Hunter valley region in NSW Australia is an area with a heavy coal mining presence. As some mines come to their end of life, options are being investigated to improve the topsoil on post mining land for greater plant growth, which may allow economically beneficial farmland to be created. This research is part of an investigation into mixing a mine waste material, coal tailings, with topsoil in order to produce an improved soil for plant growth. Implementing such a solution requires estimation of the drying path of the water retention curves for the tailings and topsoil used. Instead of a lengthy laboratory measurement, a prediction of the drying curve is convenient in this context. No existing prediction models were found that were suitable for these mine materials, hence this paper proposes a simple and efficient model that can more accurately predict drying curves for these mine materials. The drying curves of two topsoils and two tailings from Australian coal mines were measured and compared with predictions using the proposed model, which performs favorably compared to several existing models in the literature. Additionally, the proposed model is assessed using data from a variety of fine- and coarse-grained materials in the literature. It is shown that the proposed model is overall more accurate than every other model assessed, indicating the model may be useful for various materials other than those considered in this study.

Dielectric Properties of Lunar Materials at the Chang’e-4 Landing Site

On January 3rd 2019, the Chang’e-4 mission successfully landed in the Von Kármán Crater inside the South Pole-Aitken (SPA) basin and achieved the first soft landing on the farside of the Moon. Lunar penetrating radar (LPR) equipped on the rover measured the shallow subsurface structure along the motion path for more than 700 m. LPR data could be used to obtain the dielectric properties of the materials beneath the exploration area, providing important clues as to the composition and source of the materials. Although the properties of the upper fine-grained regolith have been studied using various methods, the underlying coarse-grained materials still lack investigation. Therefore, this paper intends to estimate the loss tangent of the coarse-grained materials at depth ranges of ~12 and ~28 m. Stochastic media models with different rock distributions for the LPR finite-difference time-domain (FDTD) simulation are built to evaluate the feasibility of the estimation method. Our results show that the average loss tangent value of coarse-grained materials is 0.0104±0.0027, and the abundance of FeOT+TiO2 is 20.08 wt.%, which is much higher than the overlying fine-grained regolith, indicating different sources.

Experimental study on the strength and deformation characteristics of sandy pebble soil foundation based on the equivalent density method

With the rapid development of urban construction, many bridges and subways are built on sandy pebble soil foundation. As a special kind of soil, sandy pebble soil has the characteristics of large particle size, low compressibility, low cohesion, poor self-stability, large permeability coefficient, large friction coefficient, etc. The strength and deformation characteristics of the sandy pebble soil are one of the key concerns in engineering field. Due to the size limitation of the laboratory test equipment, scaling is necessary for sandy pebble soil. The equivalent density of coarse-grained material could be obtained by equivalent density method; large-scale triaxial and interface shear tests were performed to study the comprehensive mechanical characteristics. Furthermore, appropriate models were investigated to describe the stress-strain relationships of sandy pebble soil, and the corresponding model parameters were summarized. The tests results reveal that the saturated sand pebble soil show shear shrinkage characteristics under low confining pressure, conversely unsaturated samples show shear dilatancy characteristics under low confining pressure. Under high confining pressure, obvious shear shrinkage characteristics could be observed. The shear strength parameters of unsaturated samples are obviously larger than those of saturated samples. It shows a good hyperbolic relationship between shear stress and displacement on the interface of sandy pebble soil and concrete slab, and the shear strength and normal stress are in a good linear relationship. The research could provide strong support for engineering design in sandy pebble soil.

FG-LiquID

Contact-less liquid identification via wireless sensing has diverse potential applications in our daily life, such as identifying alcohol content in liquids, distinguishing spoiled and fresh milk, and even detecting water contamination. Recent works have verified the feasibility of utilizing mmWave radar to perform coarse-grained material identification, e.g., discriminating liquid and carpet. However, they do not fully exploit the sensing limits of mmWave in terms of fine-grained material classification. In this paper, we propose FG-LiquID, an accurate and robust system for fine-grained liquid identification. To achieve the desired fine granularity, FG-LiquID first focuses on the small but informative region of the mmWave spectrum, so as to extract the most discriminative features of liquids. Then we design a novel neural network, which uncovers and leverages the hidden signal patterns across multiple antennas on mmWave sensors. In this way, FG-LiquID learns to calibrate signals and finally eliminate the adverse effect of location interference caused by minor displacement/rotation of the liquid container, which ensures robust identification towards daily usage scenarios. Extensive experimental results using a custom-build prototype demonstrate that FG-LiquID can accurately distinguish 30 different liquids with an average accuracy of 97%, under 5 different scenarios. More importantly, it can discriminate quite similar liquids, such as liquors with the difference of only 1% alcohol concentration by volume.

Grain boundary segregation induced precipitation in a non equiatomic nanocrystalline CoCuFeMnNi compositionally complex alloy

Compositionally complex alloys (CCAs) in a nanocrystalline state often involve complex and poorly understood phase transformations which can consequently result in grain growth even at low temperatures. A detailed study of the microstructure and phase stability in CCAs is challenging due to the presence of multiple principal components. In view of these challenges the objective of the present study is to establish a systematic understanding of the phase evolution in a face centered cubic non equiatomic nanocrystalline CCA (CoCuFeMnNi). To accomplish this objective, we employed in-situ transmission electron microscope heating in combination with automated crystal orientation mapping (ACOM) and energy filtered transmission electron microscopy (EFTEM) to elucidate the sequence of phase decomposition of the high-pressure torsion (HPT) processed CoCuFeMnNi. Our analysis reveals a complex succession of grain boundary segregation and depletion steps leading to the formation of a FeCo-rich secondary phase. Our results show that prior to the formation of the secondary phase, Cu, Ni and Co segregate and Fe and Mn deplete at the grain boundaries. After the FeCo precipitation is triggered, Mn segregates to the grain boundaries along with Ni and Cu, whereas Fe and Co are depleted. The FeCo precipitates have a B2 crystal structure and typically exhibit a Kurdjumov-Sachs (K-S) and/or Nishyama-Wasserman (N-W) orientation relationships with adjacent fcc grains. Ex-situ heat treated CoCuFeMnNi analyzed by atom probe tomography (APT) revealed a highly heterogeneous segregation of the different elements to different grain boundaries. The FeCo-rich precipitates contain trace amounts of Ni, whereas Cu is rejected leading to the formation of a separate Cu rich phase. This complex segregation phenomenon is assisted by the high fraction of grain boundaries and triple junctions in the nanocrystalline material, which are critical for the phase evolution in this alloy, which is not frequently observed in the corresponding coarse-grained material.

Leaching of acid generating materials and elements from coarse- and fine-grained acid sulfate soil materials

In Finland, acid sulfate (AS) soils are regarded as a serious environmental threat towards the Baltic Sea and watersheds situated in land areas that have emerged from the sea since the last glaciation due to glacial isostasy. The aim of this study is to compare the behavior of coarse-grained AS soil materials to the behavior of fine-grained AS soils and coarse-grained non-AS soils in order to (1) assess the potential environmental threat of coarse-grained AS soils and (2) to assess the need to distinguish coarse-grained AS soils from fine-grained AS soils in future risk assessment of AS soils. The hypotheses are that (1) a coarser grain size enhances the rate of oxidation and pH decrease due to larger inherited pore size, enabling better initial aeration and less efficient buffering processes due to lower particle surface areas and different mineralogy (more weathering resistant quartz and feldspars), and that (2) the leaching of acid generating materials and elements from coarse grained AS soils is significantly lower as compared to fine-grained AS soils but significantly higher as compared to coarse grained non-AS soils.The study used an incubation based “let the soil speak for itself”-approach, which means that parameters such as pH, acidity, amount of elements leached, and the electric conductivity of the leachates were measured on arrays of sample aliquots before, during, and after a 16 week incubation (oxidation) period. Even though the coarse-grained AS soil materials contained one order of magnitude less sulfide than the fine-grained AS soil materials, a S mass fraction as low as 0.01%, the pH dropped well below 4.0 upon oxidation, thus being classified as AS soils. The amount of acid generating materials and elements leached from coarse-grained AS soil materials were at least one order of magnitude less, as compared to the fine-grained AS soil materials, except for Fe, which leached in similar or greater quantities from coarse-grained AS soil materials. The differences in the leaching of acid generating materials and elements suggest it would be beneficial to divide coarse-grained and fine-grained AS soils into separate subgroups for risk management purposes.

Study of Micro-Upsetting by Finite Element Simulation Based on Crystal Plasticity and Grain Boundary Strengthening Theories

The properties of individual grains affect the mechanical behaviors and response of materials in micro-scaled deformation, viz., microforming, and there are unknown phenomena and deformation behaviors existing and limiting the wide application of microforming due to size effect. In this paper, a composite model combining crystal plasticity and grain boundary strengthening theories was developed for numerical investigation into the effect of grain boundaries on the plastic deformation of copper micro-upsetting. By comparing the results with and without grain-boundary structure, it is revealed that grain boundaries, which act as the barriers of crystal slip, result in the enhanced flow stress and the discontinuous distribution of stress and strain. The grain size effect is also considered in this research, and the results show the coarse-grained material reduces the flow stress and enhances the inhomogeneous deformation.

A comparison of the corrosion behaviour of copper materials in dilute nitric acid

The corrosion of a number of coarse- and fine-grained copper materials has been studied in an aerated aqueous nitric acid (100 mM) solution. The materials properties and the consequences of corrosion were characterized by scanning electron microscopy, electron back scatter diffraction and confocal laser scanning microscopy. The corrosion of the coarse-grained materials was shown to be strongly influenced by the crystallographic orientations of grains. For fine-grained materials grain boundary etching at high angle grain boundaries and grain boundary pores (for cold sprayed copper) overrode the influences of texture on the corrosion rate.

Effects of slurry viscosity and particle additive size on filter cake formation in highly permeable sand

Filter cake is critical to maintaining the stability of the excavation face of an underwater shield tunnel in a high-permeability stratum. In a high-permeability formation, generating an effective filter cake on the excavation face is difficult with a pure bentonite slurry, which penetrates the ground and may not achieve the required suspension pressure. Determining how to efficiently and quickly form a thin and low-permeability filter cake on the tunnel working face has become a key engineering problem in the construction of slurry shield tunnels in high-permeability strata. In this study, the relationship between slurry viscosity and the slurry pressure gradient of pure bentonite was established by performing slurry permeability experiments. The influence of slurry viscosity on the formation of the filter cake in a high-permeability formation was studied under different pressure gradients. In addition, the effect of additive particle size on the slurry filter cake formation was analyzed by introducing additives with different particle sizes to pure bentonite slurries with different viscosities. The test results indicate that (1) for the pure bentonite slurry, the critical initial pressure gradient can be used as a rough indicator of the formation of the filter cake, and the relationship between the critical maximum pore diameter and the average pore diameter of the formation can be compared to establish and analyze the formation law of the slurry filter cake; (2) adding particles to the slurry can enhance the effect of the pure bentonite slurry; and (3) adding coarse-grained materials can effectively improve the film-forming effect. The slurry is more compact when the particle size is close to the average pore size of the formation.

Phase Transformations upon Ageing in Ti15Mo Alloy Subjected to Two Different Deformation Methods

Ti15Mo alloy was subjected to two techniques of intensive plastic deformation, namely high pressure torsion and rotary swaging at room temperature. The imposed strain resulted in the formation of an ultrafine-grained structure in both deformed conditions. Detailed inspection of the microstructure revealed the presence of grains with a size of around 100 nm in both conditions. The microstructure after rotary swaging also contained elongated grains with a length up to 1 µm. Isothermal ageing at 400 °C and 500 °C up to 16 h was applied to both conditions to investigate the kinetics of precipitation of the α phase and the recovery of lattice defects. Positron annihilation spectroscopy indicated that the recovery of lattice defects in the β matrix had already occurred at 400 °C and, in terms of positron trapping, was partly compensated by the precipitation of incoherent α particles. At 500 °C the recovery was fully offset by the formation of incoherent α/β interfaces. Contrary to common coarse-grained material, in which the α phase precipitates in the form of lamellae, precipitation of small and equiaxed α particles occurred in the deformed condition. A refined two-phase equiaxed microstructure with α particles and β grain sizes below 1 μm is achievable by simple rotary swaging followed by ageing.

Fatigue properties of UFG Ti grade 2 dental implant vs. conventionally tested smooth specimens

Complicated geometry in combination with surface treatment strongly deteriorates fatigue resistance of metallic dental implants. Mechanical properties of pure Ti grade 2, usually used for dental implant production, were shown to be significantly improved due to intensive grain refinement via Conform SPD. The increase of the tensile strength properties was accompanied by a significant increase in the fatigue resistance and fatigue endurance limit. However, the SLA treatment usually used for the implants' surface roughening, resulted in the fatigue properties and endurance limit decrease, while this effect was more pronounced for the ultrafine-grained comparing to the coarse-grained material when tested under tensile-tensile loading mode.The testing of the implants is usually provided under the bending mode. Even though different testing condition for the conventional specimens tests and implants testing was adopted, a numerical study revealed their comparable fatigue properties. The fatigue limit determined for the implants was 105% higher than the one for coarse-grained and only by 4 % lower than the one for ultrafine-grained Ti grade 2.Based on the obtained results, conventional specimens testing can be used for the prediction of the fatigue limit of the implants.

Determination of the Effect of Soil Particle Size Distribution on the Shear Behavior of Sand

Many geotechnical problems require the determination of soil engineering properties such as shear strength. Therefore, the determination of the reliable values for this parameter is essential. For this purpose, the direct shear test, as one of the oldest tests to examine the shear strength of soils, is the most common way in laboratories to determine the shear parameters of soil. There are far too many variables that influence the results of a direct shear test. In this paper, a series of 10 × 10 cm direct shear tests were carried out on four different poorly graded sands with different particle size distributions to determine their shear behaviors. Four different poorly graded sands with a different median diameter or medium value of particle size distribution (D50) (0.2, 0.53, 1.3, and 2.3 mm) has been selected, and about 40 direct shear tests were conducted. It was concluded that a soil’s friction angle is affected by coarse-grained material. Accordingly, sandy soils with bigger particle sizes record a higher friction angle than soils containing small particles. The investigations also showed that sand with bigger particle sizes has a higher dilation angle. In addition, a non-linear regression analysis was performed to establish the exact relationship between the friction angle of the soil and the characteristics of the soil particles. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.