Behavior Of Sand Research Articles

Investigating Calcareous and Silica Sand Behavior at Material Interfaces: A Comprehensive Study

Abstract This study centers on the crucial determination of the mobilized friction angle between soil and various materials, including steel and concrete, to enhance the modeling of soil-structure interaction. The primary objective of the current investigation was to assess the interfacial friction between calcareous and silica sands when interacting with concrete or steel surfaces. To achieve this, direct shear tests were conducted to examine the impacts of relative density (Dr), surface roughness (Rn), and shearing direction. The test results reveal that the shear strength of calcareous sand surpasses that of silica sand when considering a specific Rn. Furthermore, the interface friction of both sand types escalates with an increase in normal stress and Rn, with higher values observed in interactions with steel plates. Notably, the friction angle ratio (the interaction friction angle over the pure sand friction angle) demonstrates minimal dependence on the sand type. The most pronounced divergence in the friction angle ratio is evident at the maximum Rn value, which increases alongside Rn values for both calcareous and siliceous sands. With increasing Rn values, the maximum shear strength, contingent on normal stress and relative density, also rises. The influence of relative density on the interaction friction angle diminishes with escalating surface roughness.

The role of incremental stress ratio in mechanical behavior and particle breakage of calcareous sand

The role of incremental stress ratio in mechanical behavior and particle breakage of calcareous sand

Study on monotonic direct shear characteristics of geosynthetics–calcareous sand interface

The investigation of shear behavior at the geosynthetics–calcareous sand interface is crucial for the internal stability design of reinforced revetment structures. A series of large-scale monotonic direct shear tests was conducted to examine the interface shear characteristics of geotextile–calcareous sand (GT–CS), geogrid–calcareous sand (GG–CS), and unreinforced calcareous sand (URCS). The interface shear behavior was investigated by considering the effects of interface types, including URCS, GT–CS, and GG–CS interfaces, and normal stresses ranging from 25 to 100 kPa. The interface interaction mechanism for different interface types is disclosed. The results indicate that embedding geotextiles and geogrids into calcareous sand filler alters the interface dilatancy behaviour of calcareous sand, which is significantly affected by normal stress. The dilatancy curves of GT–CS and GG–CS interfaces predominantly exhibit contraction–dilation and contraction, whereas the dilatancy curves of the URCS interface primarily display contraction–dilation–contraction and contraction. The shear softening behavior of GT–CS and GG–CS interfaces is primarily influenced by interface interaction mechanisms at the hardening stage and post-peak softening stage. The use of geogrid/geotextile has a reinforcing effect on calcareous sand fillers, leading to an increase of 1.22–1.44 times in interface peak cohesion. This increase falls within the range observed for geosynthetics–siliceous sand and geosynthetics–soil.

Study on micromechanical behavior and energy evolution of granular material generated by latent diffusion model under rotation of principal stresses

In this study, advanced image processing technology is used to analyze the three-dimensional sand composite image, and the topography features of sand particles are successfully extracted and saved as high-quality image files. These image files were then trained using the latent diffusion model (LDM) to generate a large number of sand particles with real morphology, which were then applied to numerical studies. The effects of particle morphology on the macroscopic mechanical behavior and microscopic energy evolution of sand under complex stress paths were studied in detail, combined with the circular and elliptical particles widely used in current tests. The results show that with the increase of the irregularity of the sample shape, the cycle period and radius of the closed circle formed by the partial strain curve gradually decrease, and the center of the circle gradually shifts. In addition, the volume strain and liquefaction strength of sand samples increase with the increase of particle shape irregularity. It is particularly noteworthy that obvious vortex structures exist in the positions near the center where deformation is severe in the samples of circular and elliptical particles. However, such structures are difficult to be directly observed in sample with irregular particles. This phenomenon reveals the influence of particle morphology on the complexity of the mechanical behavior of sand, providing us with new insights into the understanding of the response mechanism of sand soil under complex stress conditions.

Microstructural Analysis of the Effect of Using Nano-silica on the Mechanical Properties of Cement–Sand Mortar Under the Effect of Heat

The performance of cement-based materials depends on the characteristics of solid particles at the nano-scale or nanometer porosities in the interfacial transition zone between cement particles and aggregate. Heat significantly affects the properties of these particles and the connection between them. Accordingly, the present study seeks to investigate the effect of nano-silica on the strength parameters of sand–cement mortar at high temperatures. In this regard, the sand–cement mortar was prepared by replacing 5, 10, and 15 percent of cement with nano-silica. The specimens were subjected to temperatures of 25, 100, 200, 400, 600, and 800 °C after curing at the ages of 3, 28, and 90 days. The effect of high temperatures on the physical and mechanical properties of sand–cement mortar was analyzed using macro-structural tests of compressive strength, loss in weight, and water absorption, and microstructural tests of X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results revealed that the macro-structural behavior of sand–cement mortar highly depends on the microstructure and changes in cement nanostructures during heat treatment. Primary portlandite and C–S–H nanostructure were destroyed at 600 °C, and alite, belite, and β-wollastonite were formed at 800 °C. Adding nano-silica improved the strength properties of sand–cement mortar against heat, so the compressive strength of 28-day specimens containing 15% nano-silica increased from 13.9 to 19.2 MPa at a temperature of 800 °C.

Abrasive Wear Characteristics of 30MnB5 Steel for High-Speed Plough Tip of Agricultural Machinery in Southern Xinjiang Region

The high-speed plough tip is the core soil-touching component in southern Xinjiang field cultivation, but the interaction of the plough tip with the soil results in severe wear of the tip. The friction behaviour of sand and soil on plough tips was investigated with a homemade rotary abrasive wear tester in a one-factor multilevel test with three parameters: moisture content, velocity/rotational speed and friction distance. The objective was to study the friction behaviour of the sand soil and plough tip and analyse and characterise the wear amount, wear thickness and compressive stress distribution, three-dimensional wear morphology and microscopic wear morphology of the plough tips. The results show that with increasing speed, the wear amount changes more gently; with increasing soil water content, the soil adhesion force and lubricating water film increase so that the wear amount follows a second-order parabolic law; and with increasing friction distance, the wear amount gradually increases, and the wear rate also shows an upward trend when the plough tip is in the abrasive wear stage. The tip makes contact with the firmer soil with higher surface compressive stresses, causing the most wear. As the friction distance increases, sand particles become embedded in the contact surfaces, creating a groove effect along with spalling pits caused by fatigue wear. During the whole wear period, the groove effect is always accompanied by spalling pits appearing repeatedly. The analysis of the wear micromorphology of the plough tip shows that the number of flaking pits gradually decreases in the direction of soil movement, and the form of damage changes from impact wear to plough groove scratches. Abrasive wear interacts with corrosive wear to exacerbate plough tip wear.

Factors influencing static and cyclic behaviour of polymer-grouted sands

ABSTRACT In this study, thorough laboratory research was conducted in order to increase knowledge of the beneficial effect of water-soluble epoxy resin on the monotonic or cyclic triaxial strength of different sands. Seven sand fractions (with different particle sizes, uniformity coefficients and mineralogical compositions) were injected with solutions of epoxy resin and water, at ratios of 3.0, 2.0 and 1.5. To evaluate the influence of chemical treatment on the static strength behaviour of grouted sands, a series of monotonic triaxial tests on dry specimens and isotropically consolidated undrained (CIU) triaxial tests, were conducted on samples cured for 90 days. CIU cyclic triaxial compression tests were also performed, to assess improvements in the cyclic resistance of treated sands. The experiments showed that this resinous grouting resulted in an appreciable increase in cohesion values, particularly for fine sands and well-graded sands, ranging from 0.15 to 0.66 MPa. Despite the fact that friction angle values were reduced, the overall shear strength increased over a wide range of stresses. Moreover, all grouted sands exhibited a substantial improvement in cyclic properties, with failure occurring at significantly elevated stress levels and after enduring a larger number of loading cycles, compared to their untreated counterparts.

Undrained shear mechanical behaviors of dense gassy sand

Shallow gas can cause many disasters, and it is reported in many marine engineering constructions. For this, it is imperative to understand the impact of gas on the mechanical behaviors of soil. This study investigated the influence of undrained triaxial compression tests on dense gassy sand commonly encountered in coastal areas. Triaxial tests were performed on specimens with saturations of 100%, 99.8%, 95.9%, and 92.7% under confining pressures of 50 kPa and 200 kPa by a self-developed multi-purpose integrated triaxial apparatus (MITA) for gassy soil. The results are presented in terms of monotonic stress‒strain behavior, volumetric behavior, shear strength, and excess pore water pressure (EPWP). The occurrence of gas bubbles has different effects on loose and dense sands, augmenting the undrained shear strength of loose sand while concurrently diminishing that of dense sand. The deviatoric stress of dense sand increases during shear shrinkage, which is similar to the characteristics of loose sand under the influence of gas bubbles. However, following sand dilation, the effect of gas bubbles on deviatoric stress manifests in an antithetical manner. With elevated gas content, the shear strength of dense sand decreases, accompanied by a deceleration in the development of EPWP and a notable increase in volumetric changes. To this end, a microscopic explanation concerning the deformation and evolution of gas bubbles within sand during the shear process was presented to reveal the macroscopic laws governing the undrained shear attributes of dense gassy sand.

Effect of the particle shape on the shear mechanical behavior of coral sand

Abstract Coral sand particles exhibit a wide range of shapes, which can be divided into four shapes, e.g., blocky, dendritic and rodlike, flaky, and shell debris. The particle shape of these mixtures is defined by the sphericity, concavity, aspect ratio, flatness and overall regularity, which ranges from 0 to 1. The effect of particle shape on the strength, crushing characteristics, and critical state parameter is systematically investigated through a series of triaxial drainage shear tests under different confining pressures. And the relationship between critical state parameters and mechanical parameters is established. The test results demonstrate the existence of an evident strain-hardening phenomenon in the stress–strain curve of coral sand, accompanied by a strain-softening phenomenon when the bias stress reaches its peak value. The sample is initially subjected to shear shrinkage, followed by shear expansion. The volumetric deformation of the coral sand decreased with increasing peripheral pressure. The particles are transformed from rough irregular shapes to smooth spheres as evidenced by an increase in the shape parameter. The greater the degree of irregularity in the shape of the particles, the more pronounced the resulting change in size reduction. In addition, the critical state parameter was found to be influenced by the shape of the coral sand particles and the mode of particle accumulation. The overall shear resistance of coral sand particles was found to depend on particle rearrangement in addition to particle surface roughness and interparticle friction. It is proposed that the general regularity critical state parameter equation relates the particle shape of coral sand to its critical state mechanical properties, which is of great importance to the practical application and research of coral sand in engineering, and provides an effective means of predicting mechanical properties granular materials.

Multiscale simulation study for mechanical characteristics of coral sand influenced by particle breakage

This paper investigates the mechanical response of coral sand under particle breakage using a hierarchical multiscale model combining the discrete element method (DEM) and the finite element method (FEM). This DEM-FEM model links the microscopic interaction mechanisms to macroscopic phenomena such as strain localization and failure. A cohesive contact model was first utilized to simulate compaction bands in the DEM and construct a cohesive assembly with smaller particles distributed around a larger particle to better simulate the grinding and angular breakage of coral sand. A representative volume element (RVE) that includes particle breakage was then constructed and analyzed under periodic boundary conditions. DEM analysis was performed, and the results were compared with triaxial compression test data obtained from the literature, demonstrating that the constructed RVE effectively represents the mechanical properties of coral sand. The constructed RVE was used for hierarchical multiscale simulations, which showed good agreement with existing triaxial testing of coral sand. Finally, by setting a larger cohesive force, the constructed coral sand particles were prevented from breakage, and comparative analysis revealed that particle breakage weakens the mechanical properties of coral sand. Furthermore, different shapes of coral sand particles were constructed, and RVE and hierarchical multiscale simulations of triaxial tests were performed. The results indicated that the triaxial tests of long strip-shaped coral sand particles exhibit higher peak values compared to spherical coral sand particles. Additionally, a double porosity model of coral sand was constructed to analyze the impact of internal porosity on soil mechanical properties. The results showed that the presence of internal porosity significantly weakened the mechanical properties of coral sand. These findings highlight the significant impact of particle breakage and shape on the mechanical behavior of coral sand, offering important insights for engineering applications.

Influence of ground slag and dune sand behavior of binary and ternary cement

This study examines the effect of slag and dune sand replacement (binary and ternary) in cement production, focusing on key mechanical properties and chemical behavior, especially on fire loss and residual an insoluble examined at different curing times ranging from 2 to 210 days. The findings show that the addition of slag and dune sand powder significantly influences the mechanical and thermal properties of mortar mixtures replaced by slag the compressive strength increases up to 30% and a slight decrease up to 40 is observed %. Ternary mixes show improved long-term compressive strength, especially after 120, 210 days, although generally young strength is lower than control When binary and ternary are combined with high flexural strength, ternary mixes exhibit good long-term performance, especially in mixtures of 20-30% slag and 10% dune sand lime (ACHOURA, D and al. 2008). From a thermal perspective, the replacement of slag with dune sand lime reduces losses during combustion, indicating excellent thermal stability. The addition of dune sand lime increases the proportion of impervious residue, indicating stability and durability of the cement. Overall, the study concludes that the proper use of slag and dune sand lime especially in ternary mixes can significantly improve the long-term mechanical and thermal performance of cement mortars Thus these findings provide valuable insights for designing building materials with higher durability and strength to suit specific construction application applications.

INVESTIGATION OF THE SHEAR STRENGTH OF REINFORCED SILTY SAND

Introduction: This paper presents an experimental investigation that aims to study the influence of silt content, glass fiber content, and their combined effect on the shear behavior of silty sand. For this purpose, a series of tests using direct shear apparatus (as methods) were carried out on sand mixed with various silt and fiber contents. Samples were prepared with a relative density of 50 %, and each mixture was tested at three different normal stresses. The experimental results indicated an increase in shear strength at 10 % silt content, followed by a decrease in shear strength with increasing silt content from 10 % to 30 %. It was also found that 0.5 % is the optimal content that can be added to sand-silt mixtures to enhance their shear strength and friction angle, although the mixtures become more contractive.

Partial replacement of sand by fine-grained crushed waste glass along with fly ash stabilization for geotechnical applications in pavement

Natural sand (NS) is one of the most used engineering materials in almost all types of construction worldwide. Considering environmental sustainability, the replacement of natural sand with crushed glass waste (CWG) can provide a solution for both geo-environmental problems of natural sand depletion and waste glass disposal at a time, since sand and glass share almost similar chemical components. This research aimed to investigate the mechanical behaviors of natural sand replaced with fine CWG particles by 5 %, 10 %, 15 %, 20 %, 25 %, 30 %, and 35 % of dry weight. NS-CWG optimum composition was then stabilized by adding Class C fly ash (FA) from 5 to 35 % of NS-CWG to find out the optimum FA content to stabilize NS-CWG. The effects were analyzed through compaction, direct shear, and California Bearing Ratio (CBR) tests. Test results showed that maximum dry density increased, and optimum moisture content decreased due to adding CWG, and a contrasting effect was found after adding FA. 25 % FA significantly stabilized the NS-CWG mixture's strength parameters, such as increased cohesion, angle of internal friction, improved shear strength by 55.67 %, and increased CBR by 44 %. The decreased roundness index and scanning electronic microscopy (SEM) test results further evaluated and supported the improved geotechnical properties of NS + CWG + FA. The findings of the study can be useful in producing recycled materials for constructing road pavements of sustainable transport network development.

Behaviour of sand under the constant shear drained stress path: the role of fines

This paper presents a specifically designed experimental study aimed at exploring the role of fines in altering the behaviour of sand under the constant shear drained (CSD) stress path. The novelty of this study includes that the interplay of several key factors (fines shape, fines content, void ratio) was investigated systematically and the true constant shear stress condition was fulfilled by means of an advanced servo system which allowed the entire loading response to be captured. One of the marked findings is that the presence of fines not only alters the onset of instability of loose sand but also affects the deformation development thereafter. Drained instability can be triggered more easily in loose sand mixed with silica fines compared with the sand on its own. At the same quantity of fines, instability can be triggered more easily for sand mixed with rounded fines. However, the effect of fines appears to be marginal for sand at dense state. For all tested specimens, values of the axial strain rate at instability fall in a narrow range (0.008%/min–0.016%/min), meaning that the axial strain rate can be potentially a useful guide for quantitatively determining the inception of instability under the CSD conditions. The stress ratio q/p′ at onset of instability under the CSD conditions is also state dependent as under the undrained conditions.

Cemented sand under hollow cylinder multiaxial loading

Improvement of granular soils mechanical properties can be achieved by the addition of bonding agents. In this research, low amount of Portland cement was added to a sand and its beneficial shear strengthening effects were evaluated under a range of multiaxial stress paths. The influence of the orientation of the principal axes of stress and strain on the stress-strain response and failure of cemented sand has only been scarcely investigated. Therefore, this experimental investigation reports the results of a series of consolidated drained hollow cylinder torsional tests with constant principal stress path direction, ασ, varying from 0° to 90° Results were compared with the shear behaviour of the uncemented sand tested under similar loading conditions. Results show that the addition of cement to the sand matrix increases the soil strength for all multiaxial stress path directions. The suitability of two multiaxial strength criteria for reproducing the shape of the failure envelope as a function of the orientation of principal stress axis ασ has also been analysed.

Flow-Slip Stability Behavior of Calcareous Sand Treated by Microbially Induced Carbonate Precipitation Technology

Flow-Slip Stability Behavior of Calcareous Sand Treated by Microbially Induced Carbonate Precipitation Technology

Microstructure and dynamic behaviours of polyurethane-cured sea sand under traffic–load–induced stress path

Employing sea sand as fill material for roadbeds presents significant challenges due to its naturally high dispersibility and low bearing capacity, which contribute to substantial settlement deformations under traffic load impacts. In this investigation, a two-component polyurethane was applied to enhance mechanical properties of sea sand. Alterations in the microstructure and dynamic behaviours of the polyurethane-cured sea sand were observed via Scanning Electron Microscopy (SEM) and hollow cylindrical torsional shear testing. It was found that polyurethane is incorporated into the sea sand as adhesives between particles, attachments on the particles and floating adhesives. With an increase in polyurethane content, a transition from a granular to a solid state in the sand was noted, accompanied by a progressive improvement in structural integrity. This resulted in an enhanced bonding effect at interparticle contacts with diminishing relative particle movements during shearing, leading to an increase in the critical dynamic stress ratio and a decrease in the maximum damping ratio, with both ratios being higher in cured sea sand with lower polyurethane content compared to that with higher content. Additionally, high polyurethane content induced strain hardening in the cured sea sand, resulting in a higher maximum dynamic shear modulus in low-content cured sea sand compared to high-content. Furthermore, the dynamic shear modulus ratio in sea sand with high polyurethane content was found to increase with the number of vibrations.

Liquefaction behavior and shear strain-based pore pressure model of fiber reinforced calcareous sand

The generation mechanism of pore pressure plays an essential role in understanding the liquefaction behavior of sand under cyclic loading. Extensive undrained simple shear tests were undertaken to study the pore pressure and shear strain development characteristics of calcareous sand reinforced by fibers. The results show that the deformation patterns of the tested calcareous sand gradually shift from brittle to ductile failure as fiber content increases. The mechanism of pore pressure generation in calcareous sand subjected to cyclic loading is quite distinct from that of siliceous sand, exhibiting more pronounced accumulation in the initial stage of cyclic loading. Fiber reinforced calcareous sand exhibits reverse shear contraction behavior when liquefaction is imminent. A remarkable finding is the establishment of a unique correlation between pore pressure ratio and shear strain, irrespective of the fiber reinforcement. Consequently, a shear strain-based pore pressure generation model of reinforced calcareous sand is then developed to predict the pore pressure built-up trend under varying fiber content and length conditions. This model is also applicable to various testing conditions and soil types.

Exploring the Effects of Initial Fabric Anisotropy due to Preshearing Stress History in Different Directions on the Undrained Behavior of Loose Sands

Exploring the Effects of Initial Fabric Anisotropy due to Preshearing Stress History in Different Directions on the Undrained Behavior of Loose Sands

Experimental study on shear behavior of marine sands subjected to acidic conditions

Experimental study on shear behavior of marine sands subjected to acidic conditions