Pure Sand Research Articles

Experimental characterization of artificial turf infill mixtures and implementation in smoothed particle hydrodynamics numerical model

Quantifying the response of infill used to construct contemporary artificial turf is critical to the development of computational models and providing insights to reduce sports injury associated with artificial turf. In the current study, confined compression and direct shear tests were performed on typical infill materials (sand, SBR and two mixtures (33%: 67%) by-weight). The experimental tests exhibited a progression from high strength and stiffness (sand) to low strength and stiffness (SBR) with the mixtures having intermediate values. Increasing particle size, particularly sand, tended to increase the resistance of the infill to deformation. The experimental results were implemented into a soil constitutive material model and the experimental tests were simulated using a smoothed particle hydrodynamics (SPH) method to verify the implementation in a commercial explicit finite element solver. The SPH method successfully captured the initial loading up to yield, material flow and post-yield behavior, enabling large-scale particle flow that will be necessary to simulate artificial turf. The simulation results predicted the test force-displacement response well for SBR and mixture infills. The proposed methodology demonstrated the ability to measure properties of contemporary artificial turf infills in both compression and shear for pure sand, pure SBR and mixtures of the two, and use these properties to accurately represent the infill in a computational environment. The resulting model can be extended to large-scale turf models, to investigate athlete performance and injury risk when interacting with artificial turf.

Artificial Neural Network model to predict the dynamic properties of sand-polyurethane composite materials for GSI applications

This study shows the modelling of the dynamic properties of sand-polyurethane composite materials through the Artificial Neural Network method (ANN). Such properties are relevant to assess the effectiveness of polyurethane injected into the foundation soil as Geotechnical Seismic Isolation (GSI) system. Three FeedForward Neural Network (FFN) models are developed for the prediction of the shear modulus decay, the normalised shear modulus decay and the damping ratio curve. Four inputs are considered, namely the dynamic properties of pure sand and pure polyurethane, the volumetric percentage of polyurethane and the isotropic confining stress. Each model is trained and tested on a database including previous experimental results of Resonant Column (RC) tests performed on layered sand-polyurethane specimens, with polyurethane volumetric percentages varying from 10% to 30%. In all cases, the network architecture is found to be optimal with a single hidden layer and the number of hidden neurons from 4 to 6 according to the complexity of the data to be fitted. By comparing the predicted properties with the experimental results, a good prediction quality of the models is shown both in terms of the coefficient of correlation R2 and the Mean Squared Error MSE. A relative importance analysis finally reveals that polyurethane mainly affects the properties of the composite materials with its volumetric percentage, rather than its dynamic properties especially in terms of shear modulus.

Evaluation of shear strength parameters of sustainable utilization of scrap tires derived geo-materials for civil engineering applications

The devastation caused by the illegal dumping and burning of tires has been staggering. In civil engineering, using tires engineering properties has become a major concern. For this investigation, the research used locally sourced tire chips and sand. Using tire chips sand as an alternative backfill material requires less pressure and has more improved properties than traditional backfill. Four specimens were utilized in this experiment: pure sand and sand mixtures containing 20%, 30%, and 40% tire chips, respectively. Both the Direct Shear and Triaxial Apparatus, two of the most important geotechnical tools, were used to compare and evaluate the shear properties of soil and sand tire chips. 50, 100, and 150 kPa Confining pressure and normal stress have been utilized to maintain a consistent stress level. Direct shear apparatus had a circular shape with an area of 16.62 cm2 and Triaxial shear apparatus had a height of 7.2 cm and a diameter of 3.2 cm. The stress-strain behavior of both apparatuses under ordinary loading and deviatoric stress was reported. The angles of internal friction (Φ′) and cohesion (c′) were measured for both equipment and specimens with and without tire chips, and the failure planes for direct shear and triaxial tests were reported. In both the direct and triaxial shear tests, 30% of the tire chips sand exhibit the best results, respectively. The addition of tire chips may significantly improve the toughness of the soil.

The influence of polymer content on the shear wave velocities in fine sand

The usage of various polymers as an alternative in ground improvement problems is steadily gaining popularity. However, certain aspects of the usage of polymers are still not properly addressed. In this research, an experimental programme was undertaken to study the influence of various polymer contents on the shear wave velocities in granular soils. Different polymer concentrations were mixed with a uniform sand to obtain various concentrations. Resonant column tests were carried out under three different mean effective stresses considering various densities. The results suggest a significant influence of the polymer under low stress values due to the coating that reduces normal contact forces between sand grains. The influence of the coating is further seen to decrease since under higher stresses, the coatings are significantly damaged, leading to an increase in the stiffness of the specimens, the values of which are closer to that measured for pure sand.

Application and improvement of a stress partition framework-based methane hydrate-bearing sediment constitutive model for wide range confining stress

A constitutive model of methane hydrate-bearing sediment (MHBS) was recently proposed based on a stress partition framework (SPF-MHBS). To capture the mechanical behavior of MHBS under a wide range of effective confining pressures, this study introduces the equivalent granular void ratio (e*) and the particle breakage index (Br) associated with critical state variables into the original SPF-MHBS model. A comprehensive set of triaxial tests on MHBS under 0.2–20 MPa effective confining stress were simulated. The simulation results indicate that based on appropriate parameter calibration, the response of specimens under low effective confining stress can be acceptably represented using the original SPF-MHBS model. However, at high confining stress, the simulated strength of pure sand was overestimated, while that of the hydrate-bearing specimen was and underestimated. Dilatancy was also significantly overestimated at high confining stress. After introducing the e* into the original model, the performance under relatively low pressure is improved and three model parameters are reduced from the original model. After introduction of Br, the model performance is further improved at high confining stress. The improvements allow the SPF-MHBS model to provide a unified description of MHBS behavior under a wide range of confining stress.

Damping Ratio of Sand Containing Fine Particles in Cyclic Triaxial Liquefaction Tests

Sand liquefaction triggered by earthquakes is a devastating geological disaster and has emerged as an engaging topic in earthquake engineering. With an enhanced understanding of pure sand liquefaction promoted by laboratory research, there is a growing concern, following filed investigations, over the influence of fine particles on the liquefaction potential of sand containing inclusions. Efforts have been devoted to clarifying the significance of certain physical indicators (e.g., plasticity index, particle shape and gradation characteristics), and fruitful conclusions can be found in the published literature. However, the relationship between the content of fine particles and the cyclic degradation in liquefaction process seems still unclear. To fill this knowledge gap, three sets of cyclic triaxial tests were performed on various sand–fines mixtures with the dry tamping method. The experimental results revealed that (i) fine particles provided a negative contribution to the global soil structure; (ii) however, the damping ratio measured from the obtained stress–strain loops manifested its independence from the fines content during cyclic degradation. In this paper, we propose a shearing mechanism on the microscopic scale to explain the above contrasting observations. For a given soil fabric, the fine particles around sand-to-sand contact points probably break strong force chains, intensifying the threat of liquefaction. By contrast, these fines play the same role in favouring relative sliding between sand grains during both the loading and unloading stages. As the maximum stored energy and the energy loss per cycle are amplified with the same scaling factor, the damping ratio, defined as the ratio between them, should display a macroscopic invariance in triaxial tests.

Numerical study of biomass gasification combined with CO2 absorption in a bubbling fluidized bed

AbstractBiomass gasification combined with CO2 absorption‐enhanced reforming (AER) in a bubbling fluidized bed (BFB) reactor is numerically studied via the multiphase particle‐in‐cell (MP‐PIC) method featuring thermochemical and polydispersity sub‐models. A novel bubble detection algorithm is proposed for efficiently characterizing bubble morphology. The effects of several crucial operating parameters on the microscale particle behaviors, mesoscale bubble dynamics, and macroscale reactor performance of the AER gasification process are analyzed. Compared with conventional gasification, AER gasification reduces the CO2 concentration by 33.58% but elevates the H2 concentration by 32.13%. Higher operating temperature and steam‐to‐biomass (S/B) ratio promote H2 generation but deteriorate gasification performance. A lower operating pressure improves gas–solid contact efficiency and gasification performance as the increased operating pressure inhibits bubble dynamics and particle kinematics. Compared with pure sand as bed material, the mixed bed material (CaO:sand = 1:1) significantly improves gasification performance by enhancing H2 generation and CO2 removal.

Long-term feeding of sand rice (Agriophyllum squarrosum seed) can improve the antioxidant capacity of mice

Unhealthy eating habits with sugar-rich and high-fat foods can bring nutritional imbalance and other chronic diseases. At present, there is an increasing demand in regulating human sub-health through functional foods. Agriophyllum squarrosum (L.) Moq., a pioneer plant native to sand dunes with ecological restoration function, is a traditional food plant of sand regions and Mongolian folk medicine. Numerous studies have confirmed that A. squarrosum seed, also called sand rice, has high nutritional value. However, the long-term health effects of eating sand rice remain unclear. To better explore and evaluate its long-term effects, hereby, ICR mice were fed with sand rice flour at different ratios (control, 60% and 95%) for 100 days. Results show that the growth and blood glucose level curve of these experimental mice were lower and more stable than that of the control. In addition, mice fed pure sand rice ingredient (95%) gained more stable body weight and blood glucose after 28 days, which revealed that sand rice is a food with comprehensive nutritional value and rarely negatively impacts the body growth performance. Our data also demonstrates that, the content of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) provided the lowest level in the blood of mice with a diet of pure sand rice ingredient, 0.48, 4.14, 0.91, 3.03 mmol/L, respectively. Also, T-SOD and GSH-PX activity provided a high level in mice with pure sand rice gradient, which significantly increased by 36% (T-SOD) and 19% (GSH-PX) compared to the control. These results suggest that long term intake of the pure sand rice ingredients is more helpful for stabilizing blood lipid and improve antioxidant capacity and beneficial to people suffering from chronic disease. This study supplies the first animal evidence to support the claim that sand rice is a promising functional food with comprehensive nutrition in the future. We are confident that, with increasing demands of daily sand rice usage, planting A. squarrosum in the vast desert regions will further increase the local economy and ecological restoration when coping with global warming.

Effects of Soil Types and Mango (Mangifera indica L.) Humus on Growth and Survival of some Tree Seedlings in the Nursery

This study aimed to assess the effects of various soil types andorganic growing media on the growth of some tree seedlings. It wasconducted in the nursery of the Faculty of Forestry, University ofKhartoum, Shambat, during March-November 2006. Soil growing growthmedia consisted of sand, silt and clay, while the organic matter consistedof decomposed mango humus. Seeds of Tamarindus indica L., Albizialebbeck (L.) Benth. and Acacia senegal (L.) Wild. were directly sown inpolyethylene bags (10x20 cm). Seedlings shoot height, diameter, shootand root biomasses of all the species were positively significantly affectedby clay and silt media. Root growth was significantly greater in sand thanother media. Mango humus had negatively (P < 0.05) affected seedlings'growth of all the tested species. Nonetheless, seedlings' survival rate wasfar better in the sand than in the other media. Silt and clay can be used assuitable growing media; pure sand may be used if production of seedlingswith well developed root system is envisaged. However, type and sourceof organic matter should be cautiously chosen before it can be confidentlyused as a suitable growing medium

Mechanical Analysis of Palm-Fiber-Reinforced Sand through Triaxial Tests

Triaxial tests were employed to investigate palm-fiber-reinforced sand under consolidated drained conditions in this study. Sixteen series of triaxial tests were carried out to investigate the properties of palm-fiber-reinforced sand. One series of pure sand was also employed for comparison. The deviator stress, stress path, shear strength, volume change, void ratio, and enhanced coefficient of fiber-reinforced sand were studied with different fiber lengths varying from 8 mm to 20 mm and fiber contents varying in mass from 0.3% to 0.9%. The test results indicate that palm fibers were beneficial for enhancing the shear strength of the sand. Compared to the peak shear strength increase of about 10% to 20%, the critical shear strength increased much more, by a little over 100%. Therefore, the fibers played a key role in enhancing the critical shear strength of the sand but not the peak shear strength of the sand. The addition of fiber to sand resulted in prolongation of the axial strain required to reach the critical void ratio and improved the sand’s ability to resist larger deformations, enhancing its toughness. Furthermore, the critical shear strength of the sand was positively correlated with both fiber content and fiber length, and the axial strain required to reach the critical shear strength increased with increasing fiber content and length. This study provides valuable experimental data and serves as a reference for temporary reinforcement in geotechnical engineering.

Investigation of the effect of frequency on shear strength and damping of pure sand and sand stabilised with rice husk ash using cyclic triaxial tests

Rice husk ash (RHA), owing to its pozzolanic properties and wide abundance, is an additive that can be used as an alternative to cement to improve a variety of soils. Damping and shear modulus are two important soil dynamic parameters used to predict soil behaviour under dynamic loading. Therefore, in this study, materials were prepared and their specifications were determined. A cyclic triaxial device was used to determine the dynamic parameters (stress control). Subsequently, the results related to shear modulus and damping calculated for pure sand before and after stabilisation were analysed according to different percentages of stabilisers for two frequencies of 0.5 and 1 Hz. The results revealed the effect of different frequencies on the damping of pure sand, which differed for stabilised sand. In all stabilised specimens, the shear modulus decreased with increasing frequency. Additionally, the damping decreased with increasing frequency in the stabilised samples. The shear modulus increases with the increase in the amount of stabilisers. The results also showed the positive effect of partially replacing cement with RHA.

Preliminary Work on Generative Seedling Production and Clone Selection of European Black Poplar (Populus nigra L.)

European black poplar (Populus nigra L.) is a pioneer species that belongs to the Salicaceae family and occurs in riparian ecosystems. It is one of the most endangered forest species in its entire distribution area. In Croatia, black poplars are considered an economically important forest species, but mostly clones originate from crossing combinations with American and European black poplar (Populus × canadensis Moench), while a small number of clones are native black poplar. Studies on native black poplar are quite rare and the generative propagation has not been used. The aim of this study was to gain knowledge on the production of high-quality black poplar seedlings and to carry out the selection of genotypes with the aim of establishing a base for future breeding. The female black poplar tree was selected on phenotypic characteristics in the area of Forest Administration Osijek, Forest Office Valpovo. The tree was cut down in April 2019, and branches with half-open seed capsules on catkins were collected. The branches were transferred to the Croatian Forest Research Institute’s greenhouse, where the catkins opened under the influence of the high temperature. Sowing was done in different substrates to test their effectiveness. Black poplar seedlings were selected and transplanted with regard to development and height growth. The results showed differences in height growth between plants sown in two different substrates and the occurrence of fungal diseases only on plants sown in pure sand. With subsequent multiple propagation using cuttings and selection by genotype, it is expected that it will be possible to identify several clones of native black poplar that will be introduced for use in forestry in Croatia. The use of quality plants grown from seeds will increase the genetic diversity and preserve the native black poplar gene pool.

Analyzing Physical-Mechanical and Hydrophysical Properties of Sandy Soils Exposed to Long-Term Hydrocarbon Contamination

This paper aims to investigate the issue of sandy soil contamination by oil hydrocarbons. Laboratory procedures used to study conditionally pure and contaminated sands include grain-size measurements and evaluation of physical-mechanical and hydrophysical properties. The results of the analysis of sand samples using visual and microscopic studies and sieve analysis show that, unlike in conditionally pure sands, in contaminated samples, the surface of mineral particles is covered by hydrocarbon film. The presence of the latter enables micro- and macroaggregates to be formed. Studies of the physical and hydrophysical properties of sands using a technique with pre-weighed glass containers, as well as a filtering device, SPETSGEO pipes, showed that, in comparison with conditionally pure samples, contaminated specimens of sandy soils have lower densities and higher permeabilities and water yields. Testing the mechanical properties of contaminated sands on the GPP-30 direct shear apparatus using the consolidated dried shear strength method revealed an increase in the angle of internal friction with a decrease in specific adhesion compared to conditionally clean sands.

Cyclic and Postcyclic Interface Characteristics of Geotextile-Embedded Sand-Rubber Composites

A set of 48 cyclic and 12 monotonic large-scale direct shear tests was performed to assess the interface properties of sand–rubber composite along a nonwoven geotextile layer. Rubber content, semiamplitude of the shear displacement, and applied normal stress all were varied to determine the cyclic, postcyclic, and monotonic interface response of the composite system under shear loading. The test results show that adding 40% granulated rubber to pure sand caused approximately 50% reduction in the maximum mobilized interface shear stress as the loading cycles progressed. The addition of granulated rubber to the sand decreased both the damping and the shear stiffness of the interface for all values of displacement amplitude and normal stress; in particular, for the energy dissipation, the observations were associated with the higher linearity of the stress–strain relationship when adding rubber, thereby reversing the typical trend of higher damping at smaller strains or displacements. In addition, an increase in the displacement amplitude value yielded a reduction in the secant shear stiffness, but contrarily increased the damping ratio of the geotextile–composite soil interface. An increasing trend of the hardening factor was observed through the initial cycles of loading for the samples containing 40% granulated rubber, which was ascribed to the increased densification capability of the sand–rubber mixture with the progression of the loading cycles; however, this response was not captured for the pure sand–geotextile interface.

Stress-Dilatancy Behaviourof Fibre-Reinforced Sand.

This paper analyses the stress-strain behaviour of fibre-reinforced sand using the results obtained by drained triaxial compression tests presented in the literature. The general stress-plastic dilatancy equation of the Frictional State Concept has been used to describe the behaviour of fibre-reinforced sand for different shear phases. The behaviour of pure sand is taken as a reference for the behaviour of sand with added fibres. It is shown that the characteristic shear phases can only be determined when the η-Dp relationships are used, which are very rarely demonstrated in the results of shear tests presented in the literature. It has been shown that tensile strains must occur in order to achieve the strengthening effect of fibre reinforcement. A reduction in the stiffness of the fibre-sand composite is observed in the absence of tensile strains below certain threshold values.

Does Euphrates softshell turtle nest in unfavourable substratum? Description of nests from Euphrates River, Türkiye

Nest site selection differs among species based on a characteristic crucial to the embryo's survival. The identified nest-site characteristics of the Euphrates softshell turtle highlight that these turtles, like their other soft-shelled relatives, highly prefer the sandy substrate, even pure sand, to nest. However, alteration and loss of natural habitats for many decades limited the suitable oviposition sites along the Euphrates River. This study presents the uncharacteristic nest-site choice and the nesting time of Euphrates softshell turtle for the first time. I discovered four nests, as well as six unhatched eggs in a nest on 20 August 2017. This discovery extends the known nesting season-end from early June to at least mid-August for the Euphrates River. The eggs were spherical, and their size was 28.38 (±0.2, 28.1-28.6) mm on average. The nesting substrate, consisting of only 51.8% sand, was substantially dissimilar to what was previously reported. Apart from the soil texture, the nest and its site characteristics concerning nest dimension, clutch size, egg size, and distance to the shoreline concord with what was formerly reported. I conclude that many anthropogenic alterations, such as sand mining and damming and hence the scarcity of suitable oviposition sites, may have caused location and time shift of breeding and forced the turtles to nest in these uncommon soil textures.

Water retention curve of clayey sands determined from pore structure by using various methods

Besides standard approaches, the soil water retention curve (SWRC) can be estimated either from pore size distribution obtained by mercury intrusion porosimetry or from the soil freezing characteristic curve. These methods are based on simplified laws such as Young-Laplace for capillary suction or ClausiusClapeyron for cryo-suction. These laws might not be valid for clayey sands where the presence of clay particles would induce other water retention mechanisms. This study aims to assess the clay content's effect on the validity of these two methods in determining the SWRC of clayey sands. Clay sands were prepared at different clay contents by mixing pure sand with kaolin clay prior to compaction at the Proctor maximum dry density. Five clay contents (dry mass of clay divided by dry mass of soil) were considered (0, 5, 10, 15, and 20%). The reference SWRC was obtained by standard suction measurements. The results show that SWRCs estimated from mercury intrusion porosimetry and soil freezing characteristic curve are generally in agreement with the reference SWRC. However, the results obtained by the soil freezing characteristic curve are limited in terms of suction range (500 to 5 MPa) which is not appropriate for clayey sands, while those from mercury intrusion porosimetry show significant discrepancy because of the structure heterogeneity obtained by Proctor compaction.

Electrical properties of hematite and pure sand synthetic homogeneous mixture

Substances' electrical properties react promptly to minor alterations in the specimens (texture). This electrical characteristics response depends on pH and, hence, on the surface charge. In this article, we attempt to keep the synthetic specimens homogeneous. Sand and pure hematite is smashed independently and aggregated (hematite were collected from Eastern Desert, Cairo, Egypt). Electrical parameters were examined at frequencies ranging from 0.1 to 105 Hz (dry, 21 °C). The electrical range of the measured data varies considerably depending on the frequency spectrum, specimens' concentration, constitution, and/or arrangement of the components (texture). There are two conduction areas relying on frequency-dependent conductivity (two slopes). Dielectric permittivity increases linearly with concentration. Dielectric permittivity is rapidly decreasing as the spectrum expands. Jonscher's law is applicable to all electrical characteristics. The hematite conductor concentration changes in the synthetic specimens and accordingly the texture of the specimens. The study of these electrical characteristics may assist in the modeling and simulation of rock electrical properties. The relationships between the ore's nature, mineral compositions, and electrical properties are valuable for exploration methods.

FEM analysis of wasted tire chip and sand as construction material for piles

The pile foundation can be easily damaged in the earthquake event and there is a need to reinforce the foundation to protect the superstructure. The aim of this study is to propose a material for pile foundation by using wasted tire chips mixed with sand (i.e. sand-tire mixture) and study its effectiveness in an earthquake incident. This idea is learned from many sand-tire mixtures investigations. Laboratory monotonic triaxial tests were conducted based on the pure Nevada sand and sand-tire mixture (i.e. volume of sand to volume of tire was 6:4 in this study) as the input parameters for the subsequent numerical simulation. The numerical simulation was based on a centrifuge experimental results, which was also validated in this study. The simulation results show that the proposed method has a good effectiveness for a pile foundation, since the reduction in terms of the bending moment acting on the pile foundation is significant. In addition, even in the earthquake incident, the pile foundation still has the lateral support contributed from the adjacent sand-tire mixture, which is able to protect the pile foundation from buckling and fractured. This pile foundation behavior is different from that supported by the pure sand (i.e. without sand-tire mixture), which has zero lateral support to the pile foundation in the earthquake incident. However, there is an optimal reinforced length for the sand-tire mixture, where the effectiveness becomes insignificant.

Granular limestone amended sand filters for enhanced removal of nanoplastics from water: Performance and mechanisms

Effluent from wastewater treatment plants (WWTPs) has been regarded as one of the major contributors of nanoplastics (NPs) in the environment. Improving the performance of rapid sand filter (RSF) systems in WWTPs is thus in urgent need. In this study, granular limestone, a low-cost and abundant natural material, was integrated into RSF systems to enhance NP removal from water. Laboratory filtration columns packed with pure sand and limestone-amended sand were applied to remove polystyrene nanospheres (100 nm) from deionized water (DIW) and artificial wastewater (AWW) under different grain size and flow velocity conditions. Pure sand filter showed neglectable NP removal from DIW but much higher NP removal from AWW, especially when fine sand was employed. Limestone amended RSF had a significant improvement in the removal of NPs for all the tested conditions and the removal efficiency of NPs became greater with increasing amount of limestone in columns. The sensitivity of NP immobilization to flow velocity changed significantly with different combinations of filter and background solutions. Coupled effects of physical straining, electrostatic interaction, cation screening and bridging, and surface roughness controlled the retention behaviors of NPs in the columns. The higher removal efficiency of NPs by limestone can be mainly attributed to its chemical composition as well as its surface heterogeneity and roughness. Results of this study demonstrate that limestone can offer extensive application potential for enhancing the performance of RSF systems in WWTPs to remove NPs from wastewater.