Dry Silica Sand Research Articles

Erosion Resistance of Slip Cast Composite Al2O3-ZrO2 Ceramics

In this paper, erosion resistance of slip cast monolithic (Al2O3) and composite (Al2O3–t-ZrO2) ceramics was investigated by dry silica sand (SiO2) erodent. The amount of t-ZrO2 in powder mixture of Al2O3–t-ZrO2 was 5wt. % and 10wt. %. The erosive wear behaviour was studied at following impact angles of erodent: 30°, 60° and 90°. Erosion mechanisms of all prepared ceramic samples were evaluated by measuring the roughness parameters (Ra, Rz, Rmax) and weight loss, as well as analysis of surface morphology by means of scanning electron microscope (SEM).Obtained results showed that tribological properties of monolithic Al2O3 can be improved with the addition of t-ZrO2. It was also found that erosion resistance increases with the increasing amount of t-ZrO2 in the powder mixture. Generally, for all investigated ceramic samples erosion resistance decreases by the increasing erodent impact angle.

Experimental investigation on seismic behavior of scoured bridge pier with pile foundation

SummaryThis study investigated the seismic performance and soil‐structure interaction of a scoured bridge models with pile foundation by shaking table tests using a biaxial laminar shear box. The bridge pier model with pile foundation comprised a lumped mass representing the superstructure, a steel pier, and a footing supported by a single aluminum pile within dry silica sand. End of the pile was fixed at the bottom of the shear box to simulate the scenario that the pile was embedded in a firm stratum of rock. The bridge pier model was subjected to one‐directional shakes, including white noise and earthquake records. The performance of the bridge pier model with pile foundation was discussed for different scoured conditions. It is found that the moment demand of pile increases with the increase of scoured depth whereas the moment demand of the bridge pier decreases, and this transition may induce the bridge failure mechanism transform from pier to pile. The seismic demand on scoured pile foundations may be underestimated and misinterpreted to a certain degree. When evaluating the system damping ratio with SSI, the system response may not be significantly changed even if the soil viscous damping contribution is varied. Copyright © 2014 John Wiley & Sons, Ltd.

Centrifuge tests investigating the influence of pile cross-section on pile driving resistance of open-ended piles

Soil plugging in open-ended piles not only leads to an increase in compressive bearing capacity but also influences pile driving resistance. Numerous factors affect the tendency for soil plugging, for example pile geometry, penetration depth and installation method. In this study, the influence of the cross-sectional geometry of different open-ended piles (tubular, U- and sheet-piles) on the internal and external stress state at the pile toe is investigated. The underlying data were obtained from tests of pile installation (pile jacking) into dry silica sand conducted using a geotechnical beam centrifuge. During pile penetration the internal and external horizontal stresses at the pile toe were recorded to obtain the stress state inside the open-ended piles. The results are discussed with respect to the influence of the pile's geometrical properties (diameter of tubular piles, base width of U-piles and opening angle of sheet-piles) on the plugging tendency or the pile driving resistance. To conclude, a simple analytical approach based on equilibrium analyses is presented to predict the pile's bearing capacity.

Solid Particle Erosion of Short Glass Fiber Reinforced Polyester Composite

This paper investigates the physical, impact behaviour and erosive wear properties of polyester composite materials reinforced with five different glass fibre loading (10, 20, 30, 40 and 50 wt.-%). Erosive wear property is studied under different impingement angles (30° to 90°), different impact velocities (43 m/s to 65 m/s) and dry silica sand particle (350 µm) is used as an erodent material. The results indicates that in case of erosive wear composite with 30 wt.-% of glass fiber contents shows better erosion resistance both in impingement angle and impact velocity effect as compare to the other composites. The physical properties and impact strength of the investigated composites found to be improving with fiber loading. At last the morphologies of eroded surface are examined by the scanning electron microscopy to investigate the nature of wear and material damage mode.

Tunnels in sands: the effect of size, depth and volume loss on greenfield displacements

This paper examines the effect that tunnel size, depth and volume loss have on greenfield soil displacements above tunnels in sandy ground. The results of a series of plane-strain centrifuge tests performed on tunnels in a dry silica sand are examined. The cover-to-diameter ratio, C/D, of the tunnels ranged from 1·3 to 4·4. Features of greenfield settlement trough shape, both surface and subsurface, are illustrated by examining soil displacement data obtained using an image-based deformation measurement technique. The effects of tunnel size, depth and volume loss are demonstrated, and the suitability of typical fitting curves is discussed. The complex volumetric behaviour of drained soil is illustrated by comparing tunnel volume loss with the volume loss experienced by the soil. A set of equations is developed that provide a method of evaluating the change of settlement trough shape with tunnel size, depth and volume loss.

Depth profiling 137Cs and 60Co non-intrusively for a suite of industrial shielding materials and at depths beyond 50 mm

A phantom has been used to position two radiation sources, separately, when buried under dry-silica sand at depths between 5 and 50mm. A γ-ray energy spectrum was then measured at every 1mm depth. Principal component analysis has been conducted, which has led to a non-linear fit being established, allowing the depth of entrainment to be accurately inferred. The technique has been expanded for additional shielding media: water, aggregate and both wet and dry soil. The technique has also been expanded beyond the previous depth constraint of 50mm.

Experimental and Numerical Studies on Push-Up Load Tests for Sand Plugs in a Steel Pipe Pile

This paper focuses on the bearing capacity of soil plugs (internal shaft resistance) through fundamental research on the bearing mechanism of dry silica sand plugs. Push-up load tests on the dry silica sand plugs inside a model pipe pile and DEM simulations were carried out to investigate the plugging behaviour. The influences of the packing state of the soil plugs (the relative density), and the height of the plugs on the bearing capacity were investigated. Prior to the push-up load tests, element tests on the silica sand and DEM analyses were performed to characterise the silica sand and to determine suitable DEM analysis parameters. The experimental and DEM results clearly show that the push-up force increases significantly with the increase in the aspect ratio of the soil plug, H / D , and with the relative density of the soil plug. The DEM analyses show a good agreement with the experimental results when the push-up force is small. Furthermore, the DEM results reveal that only the density of the soil plug in the lower portion, adjacent to the pile tip, increases gradually with the increase in the push-up displacement as well as the increase in H / D . Hence, it is the lower portion of the soil plug that mainly controls the capacity of the soil plug.

Impact of grain-coating iron minerals on dielectric response of quartz sand and implications for ground-penetrating radar

An unexpected result of ground-penetrating radar (GPR) surveys in the Great Victoria Desert (South Australia) was the lack of returning signal in what appeared to be a favorable environment for GPR, with dry silica sand and calcrete aggregates in the near surface. We found that the dielectric response of the dry sand samples had much higher dielectric losses than comparable sands from Western Australia and that the dielectric losses are controlled by the presence of iron oxide minerals, although iron concentrations themselves are only around 0.4%. The samples contained over 90% quartz, with subsidiary amounts of carbonates, kaolin, and smectite occurring with the iron oxide minerals as a coating on the quartz grains. An acid washing procedure removed the reducible iron oxide minerals from the clay coating but left the clays substantially unaltered. Subsequent dielectric and magnetic analysis of the samples indicates that the iron oxide minerals removed during the washing process are responsible for the reduction of GPR penetration at 250 MHz from approximately 10 m to only 1 m.

Experimental assessment of 3D particle-to-particle interaction within sheared sand using synchrotron microtomography

The paper presents a quantitative assessment of particle orientation, contacts and spatial variation of void ratio in a sand specimen loaded under plane-strain conditions. The specimen has a prismatic shape, and measures 57 mm wide × 121 mm long × 180 mm high. It was prepared using a dry natural silica sand known as F-75 Ottawa sand at a dense packing, and was sheared until failure. The specimen failed along a well-defined single shear band. It was then stabilised by slowly percolating a low-viscosity epoxy. Cylindrical subsamples 8 mm in diameter and 50 mm high were cored from the stabilised specimen at regions of interest for further investigation. A synchrotron X-ray microtomography technique was used to acquire high-resolution three-dimensional images of the cores. The scans have a voxel size of 15·06 μm, which is high enough to visualise individual sand particles. Post-scanning analyses included mapping the spatial distribution of void ratio and particle contacts inside and outside the shear band. A good correlation was found between void ratio and particle contacts. Statistical distributions of particle orientation within and outside the shear band were calculated: they show that most particles inside the shear band orient in the x–y plane towards the y-axis, which is perpendicular to the shear band with angle λ in the range 70–90°. Particles outside the shear band have no preferred orientation in the x–y plane, and form chains with preferred angles of 30–60° from the direction of the applied major principal stress.

Neural network analysis for erosion wear of nickel-aluminide coatings on steel by plasma spraying

In the present investigation plasma spray inter metallic coating of Nickel-aluminide was deposited on mild steel substrates. The response of plasma sprayed nickel-aluminide coatings to the impingement of such solid particles has been presented in this work. Nickel pre-mixed with alumina powder is deposited on mild steel substances by atmospheric plasma spraying at various operating power level. The coatings are subjected to erosion wear test. An erosion test setup developed in our laboratory is used to simulate real time erosive situations. Dry silica sand of average particle size 400 micron is used as the erodent. The erosion rate is calculated on the basis of 'coating mass losses. The erosion studies are made and different velocities and impingement angles. A computational technique (ANN analysis) is used to predict the rate of erosion wear under various operational conditions. This technique involves database training to predict property parameter evolutions in process having large number of interdependent variables. This paper presents the database construction, implementation protocol and also the set of predicted results related to the erosion wear rate of nickel-aluminide coating. It is shown that the erosion wear is strongly influenced by the angle of impact. The test is conducted at room temperature i.e.27°C and 60% RH. Ni3Al coatings deposited at different power levels (10, 12, 16, 20, 24 kW) are found to exhibit different wear rate under similar test conditions.

Erosion Wear Analysis of Plasma Sprayed Ceramic Coating Using the Taguchi Technique

Erosion wear behavior of fly ash–illmenite coating was studied using dry silica sand as an erodent. A plan of experiments based on the Taguchi technique was used to acquire the data in a controlled way. An orthogonal array and signal-to-noise ratio was employed to investigate the influence of the impact angle, the velocity, the size of the erodent, and the standoff distance (SOD) on erosion wear. The objective was to investigate which design parameter significantly affects the erosion wear. It was found that the impact angle is the most powerful factor influencing the erosion wear rate of the coating. Further, when erosive wear behavior of fly ash–illmenite coating was investigated at three impact angles (i.e., at 30°, 60°, 90°), it was revealed that the impact angle is the prime factor and maximum erosion takes place at α= 90°.

Testing of Intrinsic Sorptivity for Liquid Infiltration into Initially Dry, Miller‐ Similar Silica Sands

The sorptivity (S) of a porous medium quantifies the effect of capillarity and surface forces on liquid infiltration. For infiltration into initially dry soil, S is dependent on three system attributes: the infiltrating liquid properties, the soil properties, and the maximum liquid content behind the infiltration front, θm Through the use of scaling analyses, a singular, dimensionless value of intrinsic sorptivity (S*) and an accompanying dimensionless Boltzmann transformation (Φ*) were previously derived that are independent of these system attributes for Miller‐similar materials. The existence of S* for different infiltrating liquid properties alone were tested by performing a series of experiments that examined the infiltration of either water or the aliphatic oil Soltrol 220 into an initially dry silica sand. This study extended that work to include testing of intrinsic sorptivity for different values of θm and different Miller‐similar soils. A series of 57 experiments examined the infiltration of water or Soltrol 220 into two Miller‐similar dry silica sands across a range of θm values. The results of these experiments, together with the previous ones, support the existence of S* for the experimental conditions investigated. A singular value of S* can be used to estimate sorptivity values for Miller‐similar media for a range of conditions. Likewise, Φ* can be used to generate a similarity profile for normalized liquid content in Miller‐similar media for different liquid types and θm values.

Wear Characteristics of Plasma Sprayed Nickel—Aluminum Composite Coatings

In the present investigation plasma spray intermetallic coating of nickel—aluminide was deposited on mild steel substrates. The response of plasma sprayed nickel—aluminide coatings to the impingement of solid particles has been presented in this study. Nickel pre-mixed with alumina powder is deposited on mild steel substances by atmospheric plasma spraying at various operating power level. The coatings are subjected to erosion wear test. Dry silica sand of average particle size 400 μm is used as the erodent. The erosion rate is calculated on the basis of coating mass loss. The erosion studies are made at different velocities and impingement angles. It is observed that, the erosion wear is strongly influenced by the angle of impact. The test is conducted at room temperature, i.e., at 27°C and 60% RH. Coatings deposited at different power levels are found to exhibit different wear rates under similar test conditions. Microstructure of the coating is analyzed with SEM.

Sorption of Trichloroethylene in Hydrophobic Micropores of Dealuminated Y Zeolites and Natural Minerals

Sorption of volatile organic compounds (VOCs) in low organic carbon (<0.1%) geosorbents is difficult to predict because the sorption capacity of the mineral matrix is poorly understood. This research demonstrates hydrophobic micropores can be important sorption sites for VOCs. We studied the sorption of water and TCE on three dealuminated Y zeolites ranging from hydrophilic (CBV-300) to hydrophobic (CBV-720 and CBV-780), with the surface cation density decreasing from 2.07 to 0.42 and 0.16 sites/ nm2, respectively. Water sorption and dehydration data indicate water affinity of the zeolite micropores decreases with micropore hydrophobicity. TCE sorption on the wet zeolites decreased with increasing surface cation density. At a relative pressure (P/P0) of 0.136, TCE filled only 0.034% of the micropore volume in wet CBV-300, but 16.9% and 18.6% in wet CBV-720 and CBV-780, respectively. TCE desorption data from dry and wet silica sand (Min-U-Sil 30), kaolinite (KGa-1), and smectite (SWy-1) confirmed VOC sorption in wet microporous minerals is controlled by both the micropore volume and hydrophobicity. Results suggestTCE adsorbs in hydrophobic micropores by displacing loosely bound water, consistent with the theoretical considerations indicating the process of transferring loosely bound water from hydrophobic micropores to the bulk phase is energetically favorable.

Investigating six-degree-of-freedom loading of shallow foundations on sand

Laboratory studies of the response of shallow foundations have previously considered only planar loading. This paper describes experimental work carried out using a loading device that applies general loading onto model shallow foundations. The loading, involving all six degrees of freedom [vertical (V), horizontal (H2, H3), torsion (Q) and overturning moment (M2, M3)], has been applied to a 150 mm diameter circular flat rough foundation on a loose dry silica sand. Aspects of the loading rig design are briefly described, but the main focus is the presentation of the experimental results. These provide evidence for the generalisation of existing work-hardening plasticity models from planar loading to general loading conditions. This evidence is used to extend an existing numerical model to the six-degree-of-freedom case, and the simulation results are compared with the experimental results.

Deformation Behavior of Cold Upset Forming of Sintered Al-Fe Composite Preforms

Cold upsetting experiments were carried out on sintered Al–Fe preforms in order to evaluate their deformation characteristics. The effects of iron content and initial fractional density of the preforms on deformation behavior have been investigated thoroughly by using graphite as a lubricant. Cylindrical preforms with different initial theoretical density and aspect ratio (0.75) were prepared using a suitable die, a punch and a die bottom insert on a 1.0 MN capacity Universal testing machine. The preforms were well covered with dry fine silica sand and sintered in an electric muffle furnace at 550±10°C for a period of 1 h and then furnace cooled. Cold deformation experiments were carried out in several steps. Dimensions such as height, contact, and bulged diameters and densities were measured for each test. In general, each compact was subjected to an incremental compressive loading in steps of 0.005 MN until fine cracks appeared on its free surface. Analysis of the experimental data has shown that the power law relationship between fractional theoretical density ρf/ρth and eεz−εθ has been established. This remained valid for 0–8% iron content and all initial preform densities. Further it was found that the preforms of higher iron content shows higher values of deformation properties like the axial stress and the Poisson’s ratio than less/without iron preforms provided that the initial fractional density taken is kept constant.

Some Aspects of Cold Upset Forming of Sintered Aluminum Preforms Using Different Lubricants

Cold upset forming and densification features in sintered aluminum preforms using different lubricants were investigated. Cylindrical preforms with initial density 91% of the theoretical one and aspect radio 0.75 were prepared on a 0.1 MN capacity universal testing machine. The preforms were covered with dry fine silica sand and sintered at 520±10°C for 1 h. Cold deformation experiments were carried out in several steps. In general, each compact was subjected to compressive loading in steps of 0.01 MN until fine cracks appeared on its free surface. The experimental data showed that grease exhibits enhanced densification compared to that for MoS2 or graphite lubricants, provided that the initial preform density and aspect ratio are kept constant. The instantaneous strain hardening exponent and strength coefficient of the preforms were calculated and found to reach a peak value when the deformation or packing density were low. Further, they decreased and became constant. The initial geometry of the P/M preforms was shown to play a predominant role in influencing them.

Some aspects of cold upset forming of sintered aluminium preforms using different lubricants

Cold upset forming and densification features in sintered aluminium preforms using different lubricants were investigated. Cylindrical preforms with an initial theoretical density of 91% and 0.75 aspect ratio were prepared using a suitable die, a punch and a die bottom insert on a 1.0 MN capacity universal testing machine. The preforms were well covered with dry fine silica sand and sintered in an electric muffle furnace at 520 ± 10°C for a period of 1 h and then furnace cooled. Cold deformation experiments were carried out in several steps. Dimensions such as height, contact and bulged diameters and densities were measured for each test. In general, each compact was subjected to compressive loading in steps of 0.01 MN until fine cracks appeared on its free surface. Analysis of the experimental data showed an increasing trend in the value of exp(ϵz-ϵθ). Further, it was found that preform lubricated with lithium grease exhibited enhanced densification compared to that for MoS2 or graphite lubricant, provided that the initial preform density and aspect ratio were kept constant. The instantaneous strain hardening exponent ni and strength coefficient ki of the aluminium preforms were calculated and found to reach the peak value when the deformation or packing density was at low value. Further, it was observed that the value of ni and ki decreased and was found to be constant for both the lubricant preforms tested. It was established that the initial geometry of the PM preforms played a predominant role in influencing both ni and ki.

Some aspects of cold upset forming of sintered aluminium preforms using graphite lubricant

Cold upset forming and densification features in sintered aluminium preforms were investigated. Cylindrical preforms with four initial theoretical densities of 81, 85, 88 and 90% possessing three different aspect ratios of 0.50, 0.75 and 1.0 were prepared using a die and punch assembly with a 1.0 MN capacity hydraulic press. The preforms were packed in covered dry fine silica sand before the sintering operation was carried out in an electric muffle furnace at 525 ± 10 °C for a period of 1 h, and subsequently they were furnace cooled. Cold deformation experiments were conducted in incremental deformation steps. The experimental data showed that the ratio of the density of the preform after deformation/theoretical density of the fully dense material ρf/ρth value demonstrated an increasing trend with increasing value of exp (ϵz - ϵθ), where ϵ z is the true strain in the axial direction ϵθ is that in the hoop direction. It was established that a lower aspect ratio preform exhibited enhanced densification compared with the higher aspect ratio preforms, for any given initial preform density. Moreover, the applied stress had the tendency to increase rapidly during the initial stage of densification, thereafter continuing to increase at a low rate, as the densification was enhanced. The increase in applied stress was found to be associated with the combined effects of densification on the geometric and general work hardening parameters.

Potassium ferrate [Fe(VI)] does not mediate self-sterilization of a surrogate mars soil

BackgroundMartian soil is thought to be enriched with strong oxidants such as peroxides and/or iron in high oxidation states that might destroy biological materials. There is also a high flux of ultraviolet radiation at the surface of Mars. Thus, Mars may be inhospitable to life as we know it on Earth. We examined the hypothesis that if the soil of Mars contains ferrates [Fe(VI)], the strongest of the proposed oxidizing species, and also is exposed to high fluxes of UV radiation, it will be self-sterilizing.ResultsUnder ambient conditions (25°C, oxygen and water present) K2FeO4 mixed into sand mineralized some reactive organic molecules to CO2, while less reactive compounds were not degraded. Dried endospores of Bacillus subtilis incubated in a Mars surrogate soil comprised of dry silica sand containing 20% by weight K2FeO4 and under conditions similar to those now on Mars (extreme desiccation, cold, and a CO2-dominated atmosphere) were resistant to killing by the ferrate-enriched sand. Similar results were observed with permanganate. Spores in oxidant-enriched sand exposed to high fluxes of UV light were protected from the sporocidal activity of the radiation below about 5 mm depths.ConclusionBased on our data and previously published descriptions of ancient but dormant life forms on Earth, we suggest that if entities resembling bacterial endospores were produced at some point by life forms on Mars, they might still be present and viable, given appropriate germination conditions. Endospores delivered to Mars on spacecraft would possibly survive and potentially compromise life detection experiments.