Behavior Of Sand Research Articles

A chelation process by an amino alcohol electrolyte additive to capture Zn2+ and realize parallel Zn deposition for aqueous Zn batteries

Zn anode experiences dendrite issues in aqueous Zn batteries. They result from uneven Zn2+ flux and Sand behavior depending on the current density. Herein, the amino alcohol of 2,2′,2′′-nitrilotriethanol (NTE) additive with chelation ability is introduced to achieve stable and parallel Zn deposition. NTE preferentially adsorbs on Zn surface, which chelates with Zn2+ at interface upon geometry transformation. It not only homogenizes Zn2+ flux to inhibit dendrites at low current densities, but also supply sufficient Zn2+ to delay Sand behavior at high current densities. Parallel growth of Zn hexagonal plates is realized. Thus, Zn plating/stripping in symmetric cells at 10 mA cm−2 reaches >1600 h cycle life with the addition of 2.5% NTE in the ZnSO4 electrolyte, corresponding to a high cumulative plated capacity of 8.5 Ah cm−2. At the conditions of 5 °C or 70% depth of discharge, the lifespans of symmetric cells also extend to 6977 h and 230 h, respectively. In anode free full cells, a Zn2+ pre-inserted V6O13·H2O cathode retains 250 mAh g−1 capacity after 300 cycles at 6 A g−1, superior to 83 mAh g−1 with NTE free electrolyte.

Modification of the Reloading Plastic Modulus in Generalized Plasticity Models for Soil by Introducing a New Equation for the Memory Parameter in Cyclic Loadings

Nowadays, with the widespread supply of very powerful laboratory and computer equipment, it is expected that the analyses conducted for geotechnical problems are carried out with very high precision. Precise analyses lead to better knowledge of structures’ behavior, which, in turn, reduces the costs related to uncertainty of materials’ behavior. A precise analysis necessitates a precise knowledge and definition of the behavior of the constituent materials, which itself requires applying an appropriate constitutive model to show the behavior of materials. Constitutive models used in the generalized plasticity framework are very powerful constitutive models for the simulation of sand behavior. However, the simulation of a cyclic behavior in these models, especially the simulation of the undrained cyclic behavior, is not well-recognized. In this study, in order to eliminate the weakness of generalized constitutive models under cyclic loading, a new equation is presented to substitute the so-called coefficient of the discrete memory factor to consider the loading history in such a way that the plastic modulus is modified during reloading and, as a result, more appropriate predictions of sand behavior are obtained. The performance accuracy of the proposed coefficient was evaluated in accordance with the experimental data. Finally, the results show that after using the modification of the loading history coefficient, predictions of the constitutive model are significantly improved.

Behaviour of the aeolian sands under true-triaxial conditions

Behaviour of the aeolian sands under true-triaxial conditions

Enhancing Mechanical Behavior of Silica and Calcareous Sand through Polyurethane Foam, Nanomaterial, and Fiber

Enhancing Mechanical Behavior of Silica and Calcareous Sand through Polyurethane Foam, Nanomaterial, and Fiber

Seismic response of combined piled raft foundation using advanced liquefaction model

The design of earthquake resistant structures founded on combined piled raft foundation (CPRF) mainly depends on raft-pile-soil interaction (RPSI). This interaction become more complex for these heavy structures, if founded on the liquefiable soil. The CPRF is considered to be useful foundation in practice to support such heavy structure; in which both raft and pile increase the bearing capacity of the soil. Where raft reduces the liquefaction induced settlement and piles help to transfer the load of the structure to the non-liquefiable soil layer. The aim of this paper is to carry out the 3D nonlinear finite difference analysis of CPRF considering the RPSI. A recently developed constitutive model i.e. CycLiq for the liquefaction modelling of the soil is utilized to represent the behaviour of sand in inelastic range which consider the cyclic behaviour and large post-liquefaction shear deformation of sand. The validation of the model is carried out with the centrifuge data. The effect of CPRF over the raft and pile group is carried out for harmonic excitation with varying frequency and earthquake motion with varying PGA. The study provides important observations and insights that were not previously evident. The findings emphasize the need to consider frequency effects, geometrical nonlinearity, and material nonlinearity in the design of NPP structures. Additionally, the study introduces the application of the CycLiq liquefaction model and the development of a user-defined material for FLAC3D. Further, the outcome shows the useful conclusion on the importance of CPRF foundation over the conventional foundation i.e. raft and pile group in the liquefiable soil. It is found that excitation frequency, ground motion PGA, porosity of sand and pile spacing of CPRF have great effects on the response.

Triaxial behavior of unreinforced and geogrid-reinforced calcareous gravelly sand: Experiment and discrete element modelling

Geogrid reinforcement is a feasible technique for improving the mechanical and deformation behaviors of calcareous gravelly sand that is predominantly distributed in reclaimed foundations as construction materials. However, the shear behavior of geogrid-reinforced calcareous gravelly sand still remains unclear. In this paper, a series of large-scale drained consolidated triaxial compression tests (the specimen 300 mm in diameter by 600 mm in height) were conducted to investigate the effects of confining pressure, moisture content and geogrid inclusion on the mechanical and deformation behaviors of calcareous gravelly sand. The dilation effect, strain-softening behavior, reinforcing effect and particle breakage characteristics of unreinforced and geogrid-reinforced calcareous gravelly sand were comprehensively analyzed and discussed. Additional analysis was also performed from a microscopic perspective using the three-dimensional discrete numerical modelling. The experimental results indicate that calcareous gravelly sand exhibited a greater resistance to strain-softening tendency, and produced a higher susceptibility to crushing under the same input energy than calcareous coarse sand. Geogrid inclusion can effectively mitigate the susceptibility of calcareous gravelly sand to volumetric dilation through constraining the lateral expansion within the reinforced zone, and thus substantially increased the peak shear strength. Moreover, particle breakage appeared to be insensitive to geogrid reinforcement and water content, but increased significantly with increasing confining pressures. The numerical results further indicate that the mechanical response of geogrids was regulated by axial strain and confining pressure. As axial strain was greater than 10%, increased confining pressure resulted in a wider area of stress concentration within the geogrid meshes, and the upper geogrid sustained a greater contact force and tensile strain. The findings in this study are of practical significance for the design and construction of structures in calcareous gravelly sand reinforced with geogrids.

Improvement of a hypoplastic model for sand under undrained loading conditions

An important drawback of the hypoplastic model is the inaccurate prediction of the sand behavior under undrained monotonic loading conditions. The model is not able to reproduce the limited liquefaction type response widely observed in undrained tests on loose sand, and it often underestimates the initial stiffness and hardening rate of sand during the shearing. To address these issues, three novel modifications are introduced into a basic hypoplastic model to enhance its undrained predictive capability. Firstly, a new factor is added to the nonlinear term of the model, allowing the simulation of a purely elastic response at the beginning of loading. By doing so, the model can accurately capture the initial stiffness and undrained effective stress path of sand. Secondly, the characterized void ratios are related to an evolving state variable, enabling the model to reasonably reproduce the limited flow response and quasi-steady state. Furthermore, a new term is incorporated into the deviatoric part of the strain rate to adjust the hardening rate of the model. The model performance for undrained loading is significantly improved through the above modifications, as evidenced by the good agreement between simulation results and experimental data for tests with varying densities and confining pressures.

Ground Tire Rubber as a Sustainable Additive: Transforming Desert Sand Behavior

Managing waste tires presents a significant challenge globally, particularly in regions experiencing high temperatures and shortage of landfill sites. This issue is affecting countries like Kuwait, where the abundance of waste tires is a major source of environmental and safety risks, particularly during the intensely hot summer months. This extreme heat has sparked numerous fires, leading to substantial air pollution due to thick black smoke. Given the limited disposal options, recycling waste tires and finding practical applications for ground tire rubber (GTR) is essential. To address the challenge, a comprehensive laboratory testing program was conducted, using locally produced rubber aggregates as an additive to Kuwait's local surface sands. Two new variables were examined namely the size and gradation of the GTR, and the density of the compacted mixes. For this purpose, two different sizes of rubber aggregates, fine and coarse produced locally, were utilized, and the impact of relative compaction on the strength and compressibility of the mixtures was investigated by testing samples compacted to the maximum density and to 95% of the maximum density. The results suggest that combining local surface sands with rubber tire additives results in a lighter, more permeable, and compressible material, contributing significantly to sustainable waste management. With 20% rubber additive the maximum dry density decreased by nearly 20%, and the permeability increased by 1.74–3.11 times and the compression index increased by 6.15 and 3.8 times with fine and coarse rubber respectively. The angle of friction remained unchanged at 36° with the addition of coarse rubber and decreased by 3°–4° with fine rubber. The change in behavior although not an increase in the strength and stiffness, offers a range of suitable practical applications in civil engineering and environmental management, including use as a drainage layer, embankment construction on soft ground, earth fill around retaining walls, an additive in asphalt mixes, and in manufacturing compressible tiles for sports facilities.

Stress stress-strain behavior of hydraulic filled coral sand subjected to internal erosion

Coral sand foundations lose fine particles under the action of groundwater infiltration. As the soil skeleton structure deteriorates, the foundation becomes uneven and may even collapse. In this study, a triaxial drainage shear test of coral sand is used as a quantitative control method for the loss of fine particulate soil, and the effect of internal erosion on the mechanical behavior of coral sand is evaluated. An experiment is used to demonstrate that erosion leads to a decrease in the peak shear strength and residual strength of coral sand. Erosion has different effects on coral sand with different fine particle contents, and the effects on the friction angles of coral and terrestrial sand are also different. The secant modulus E50 and peak secant modulus Ep gradually decrease as the loss of fine particles increases. The effect of fine particle loss on the peak secant modulus Ep is significant at fine-particle losses exceeding 10% for a fine-particle content of 20%. The loss of fine particles creates new pore spaces in the coral sand, which, in turn, affects the stability of the original soil skeleton. Erosion has been shown to have an effect on the gradational features of coral sand, leading to the phenomenon that the dilatancy effect increases as a function of the amount of erosion that takes place. To prevent uneven foundation settlement caused by subsurface erosion in engineering designs, it is important to consider the gradation characteristics and fine particulate content of coral sand, which affect the stability of coral reef foundations.

Model test and numerical analysis of shield tunnel face instability in sandy soil with strain-softening properties

During excavation of a shield tunnel in a sandy stratum, variations in the state of the sand affect the stratum stability of the shield tunnel face. When dense sand is loaded, its strength decreases gradually owing to dilatancy and it exhibits strain-softening behavior. Model tests and finite element numerical simulations were performed to clarify the failure characteristics of the tunnel face induced by strain-softening. In the model tests, a dense sand stratum was constructed; the movement of the supporting plate of the excavation face was controlled to simulate the progressive failure of the shield tunnel face. Based on a material state-dependent plasticity model, a numerical analysis model of the tunnel face was established to capture the strain-softening behavior of dense sand by including a nonlocal regularization technique. Comparing the model test and numerical simulation results, the evolution of the material state of the sand with progressive failure of the tunnel face was analyzed, and the failure characteristics caused by the strain-softening of sand were revealed.

Evaluation of large axial strain of granular sand in post-liquefaction stage using DEM simulation

Field investigations in recent studies have revealed that significant damage to foundations often occurs in the post-liquefaction stage, during which sand undergoes substantial deformation. As a result, numerous researchers have dedicated considerable effort to studying the evolution of the axial strain at this stage. However, the accurate measurement of the exact value of this strain is challenging mainly owing to the limitations of the triaxial apparatus. In this study, the numerical method of discrete element method (DEM) is used to simulate undrained cyclic triaxial loading tests according to a large number of loading cycles. The mechanical behaviour of granular sand under different cell pressures was reproduced using the DEM method, wherein the liquefaction resistance increased with the cell pressure. The post-liquefaction axial strain exhibited a similar pattern of variation among the calculated cases at different cell pressures. The value of the double amplitude of the axial strain stabilised at a maximum value after a certain loading cycle. The microscopic characteristics derived from the DEM calculations, including the contact number and force chain network, were analysed to provide reasonable explanations. The sand fabric was re-established after a large number of loading cycles and controlled by cyclic loading, which helped stabilise the accumulated axial strain.

Investigation of particle size effect on particle breakage of carbonate sand under one-dimensional compression

Previous studies on the particle-size effect have indicated that larger particles tend to exhibit lower strength under equivalent loading conditions; however, the underlying mechanism remains unclear. This study investigated the influence of particle size on the macrocompression behavior of carbonate sand by performing one-dimensional compression tests on various uniformly graded samples. The variations in particle size and shape resulting from particle breakage during compression were quantitatively analyzed. In addition, X-ray micro-tomography (μCT) is employed to obtain microstructural insights into the intra-particle porosity of carbonate sand particles, and its role in the particle size effect was further discussed.

Anchor chain profiles in sand based on centrifuge model tests

The rapid development of floating wind turbines (FWTs) has brought new challenges to their mooring systems in shallow water of 50-200 m. The sand seabed, which is widely distributed in offshore regions, is often encountered in the service of FWTs and influences the anchor and mooring line design. The anchor chain is primarily adopted as the part interacting with the seabed, and its configuration in the seabed is vital for anchor design. However, a complete understanding of the chain configuration in sand is yet to be achieved. To address this, a group of centrifuge model tests using a model chain were conducted to simulate the chain embedment behavior in carbonate sand. During the tests, the chain position and soil deformation were captured using the Particle Image Velocimetry (PIV) method. A calculation model was adopted to predict the chain configuration in the sand, compare it with the centrifuge test results, and then analyze the differences between them. Finally, suggestions for model improvement were discussed.

Modified SANISAND‐F model for simple shear path

AbstractSimple shear behavior of sand is representative in geotechnical engineering with potential failure occurred along a thin shear zone. The strength and deformation of sand under simple shear are accompanied with principal stress rotation (PSR). This study proposes a modified SANISAND‐F model to capture the simple shear behavior of sand with PSR. A new plastic flow rule along with a kinematic hardening modulus is proposed to consider the evolution of the PSR and intermediate stress ratio. The developed model, with thirteen parameters, can reasonably the capture the stress‐strain and PSR of sand under simple shear.

Lateral loading response of monopiles in sand considering installation effect

The effect of pile installation is a critical issue in the analysis and design of pile foundations but it is commonly ignored due to various numerical difficulties. In this paper, the installation process of an open-ended pipe pile into a sand deposit is simulated by using the zipper technique combined with the Arbitrary Lagrangian-Eulerian (ALE) method in the framework of three-dimensional (3D) finite element modeling. The subsequent lateral load response of the pile is also simulated and compared with that without consideration of the pile installation. The state dependent behavior of sand in associated with the pile installation and the subsequent lateral load is described using an advanced constitutive model. The study shows that for a relatively loose sand deposit, the sand surrounding the pile exhibits contraction and the disturbance zone takes the form of a trapezoid, whereas for a dense sand deposit, the sand near the pile will dilate and the disturbance zone takes the form of an inversed trapezoid. Furthermore, the deformation mode of the surrounding sand under the lateral load differs to some extent from that without consideration of the installation effect. Particularly, the location of the rotation point for the laterally loaded pile tends to move downwards when the pile installation process is considered.

Effect of cementation on the mechanical response of sands using acoustic emission technique

This study investigates the impact of cementation on the mechanical behavior of sands with various cement content (CSR) in drained triaxial compression, employing both Acoustic Emission (AE) and Environmental Scanning Electron Microscopy (ESEM) measurements. The experimental findings, encompassing quantitative statistics of stress-strain relations, microstructure variations, and AE characteristics, demonstrate that: the addition of CSR from 1% to 20% leads to an exponential rise in peak strength and stiffness, marking a transition from ductile to brittle mechanical failure, which is pinpointed between CSR levels of 5% to 10%. AE characteristics unveil an upward-opening parabola of normalized AE hits with CSR, a clear transition zone identification, and three distinct types of AE rate evolutions corresponding to failure patterns of ductile bulging, shear banding, and brittle fracturing, respectively. It suggests an intimate correlation with the intrinsic differences in micro-mechanical behaviors and AE propagation properties of cemented sands with varying CSRs. Notably, the bulging and shear banding processes are divided by AE into three stages, whereas fracturing is characterized into five stages. Two precursory AE anomalies associated with incipient failure and complex failure modes are observed, emphasizing the advantage of using AE to reflect the internal micro-mechanical behavior of cemented sands over conventional stress-strain manifestations.

Influences of the Decomposition Atmosphere and Heating Rate on the Pyrolysis Behaviors of Resin Sand

The pouring of sand casting is accompanied by severe heat conduction, and there is an urgent need to investigate the pyrolysis properties of foundry sand. The main purpose of this study was to investigate the pyrolysis behaviors of resin sand, including precoated sand (PCS), hot box sand (HBS), and warm box sand (WBS), at heating rates of 20 °C/min, 30 °C/min, and 40 °C/min in nitrogen and air atmospheres. The mass loss of the resin sand was monitored continuously with a simultaneous thermal analyzer, and the kinetic parameters of the resin sand were calculated based on the Coats–Redfern method and thermal data. The average mass loss of the resin sand during pyrolysis was 3.03%, which was much smaller than that of the other sands. The volatile release characteristic index of resin sand could not be calculated based on this concept. To solve this issue, the term Tstv/mloss was established, and its value was determined. With increasing heating rates from 20 °C/min to 30 °C/min and from 30 °C/min to 40 °C/min, the mass losses of the resin sand increased by 0.79% and 0.64%, respectively, and the volatile release characteristic indices of the resin sand increased by 3.8 × 10−10 and 1.06 × 10−9, respectively. In addition, the mass losses and volatile release characteristic indices of resin sand in an air atmosphere were greater than those in a nitrogen atmosphere. With increasing heating rate, the activation energy of the resin sand decreased in a nitrogen atmosphere. The findings concerning the thermal decomposition behaviors of resin sand provided a theoretical basis for the pouring step of the sand casting process.

Experimental Study on the Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand

In this investigation, coral sand is presented as a sustainable substitute for conventional river and machine-manufactured sand. This study comprehensively investigated the macro-scale strength, deformation, and permeability characteristics of coral sand, alongside analyzing the mechanical behavior, deformation, and permeability under various conditions and in relation to distinct particle characteristics. It revealed that coral sand primarily consists of biotite and high-Mg calcite, featuring abundant internal pore space. Its compressive properties resemble clayey soils, displaying minimal unloading rebound and predominant plastic deformation during compression. In direct shear tests, the stress–strain relationship follows an approximate hyperbola, with no pronounced strain softening. Describing particle fragmentation in the process proves challenging, making indicators like internal friction angle less applicable in engineering. Triaxial tests indicate a rapid initial bias stress increase, followed by a gradual decrease post-stress peak, suggesting a strain softening phenomenon. As surrounding pressure rises, the axial strain needed to reach peak strength also increases. The permeability coefficient of coral sand correlates linearly with pore ratio increase, represented by 10e. The complex interaction of multiple factors influences the strength, deformation, and permeability of coral sand blown fill mixes, with specimen porosity having the greatest impact. The design and construction of high-weight foundation elements in coral sand blown fill projects should consider porosity effects.

Revisiting the effect of relative density on cyclic liquefaction of clean and silty sands: the crossing effect

Liquefaction of clean and silty sands remains to be an important problem during earthquakes. Even though many factors are known to influence liquefaction behavior, the influence of density index parameter and fines content (FC) are among the most important parameters. In this study, the effect of relative density (Dr) on liquefaction behavior of clean and silty sands was investigated by cyclic direct simple shear tests on two different silty sands at various FC. Several different relationships affected from Dr are revisited or investigated including number of cycles to liquefaction (NL) and cyclic resistance ratio (CRR). It was found that liquefaction resistance-fines content-relative density relationship is much more complex than previously thought. This is because CRR-Dr lines of clean and/or silty sands may cross each other at specific relative densities, which may cause the liquefaction resistance of a clean sand to be either smaller, equal or greater than the liquefaction resistance of a silty sand with the same base sand dependent on the magnitude of relative density. The mentioned behavior is also confirmed on different clean and silty sands tested in literature.

Influence of non-plastic fines and density state on stress-dilatancy behavior of coral sand: an experimental investigation

Influence of non-plastic fines and density state on stress-dilatancy behavior of coral sand: an experimental investigation