Sand Particle Size Research Articles

Liquefaction Resistance of Sand-Kaolin Mixtures: Effect of Sand Sizes

Grading characteristics, particle sizes, particle shapes and fines content are the factors contributing to liquefaction incidents besides major factors such as earthquake magnitude. Recent publications and reports from incidents of liquefied or potential liquefied soils show some evidence that the size of sand particles, particle shapes and grading characteristics will increase or decrease the liquefaction resistance. However, to date the results are still disputed and need to be expanded. Hence, the aim of this paper is to investigate the effects of different sizes of sand in sand-kaolin mixtures on liquefaction resistance. The liquefaction resistance of sand mixtures with the application of different sizes of sand-coarse sand, medium sand and fine sand mixed with fines (kaolin) content (0%,10%, 20%, 30%, and 40%) are investigated through a cyclic triaxial test under undrained conditions. Each reconstituted sample was prepared with a target relative density of 15% (loose state) and 5% of initial moisture content for the triaxial test. Effective consolidation pressures of 100 kPa were applied on the cyclic triaxial tests. Microstructure analysis on the soil samples were carried out to explain the behaviour of the samples tested. The centrifuge test was carried out on selected samples so that the behaviour of the soils in actual conditions could be visualised. The results clearly show that the liquefaction resistance was reduced at reduced sand sizes. At a constant fines content for each parent sand, the liquefaction resistance decreased with an increase of fines content up to certain percentage, then increased thereafter. The fth decreased from 30% to 20% of fines content with a decrease in parent sand sizes. The outcomes of this study are useful to advance the understanding of the behaviour of sand mixtures with different sizes of sand for design purposes.

Suffusion of a sand–clay mixture: impact of the ionic-concentration gradient, clay type, sand-grain size and hydraulic gradient

Internal erosion by suffusion within a sand–clay mixture may occur as detachment of clay particles, which is induced by a decrease in ionic concentration (IC) along with application of a high hydraulic gradient. Through designed laboratory soil-column experiments, this study investigates the impact of the IC gradient (stepwise or gradual decrease), clay mineralogy, sand particle size and hydraulic gradient on the suffusion of a sand–clay mixture. The observed breakthrough concentration of clay particles revealed the substantial suffusion of a sand–clay mixture caused by a stepwise decrease in the IC for kaolinite and illite, while similar filtrated quantities of bentonite were observed for stepwise and gradual decreases in IC. In addition, the small-grained sand showed a relatively high susceptibility to suffusion by a stepwise decrease in IC, most likely because of the low reattachment of detached clay particles. The mass of filtrated clay particles evaluated from the area of the observed breakthrough curves in this study provides a clear insight into the need to incorporate the IC gradient when assessing the susceptibility to the suffusion of clay-containing soils.

Experimental investigations of soil fluidization by an upward water leak jet

ABSTRACT In this paper, a fluidized granular sand bed by a vertically upward water leak jet was studied experimentally. It was found that an increase in the size of sand particles decreases the height of the fluidized zone, and vice versa. By increasing the cover depth, the height and area of the fluidized and mobilized bed zones are reduced. Dimensions of the fluidized zone increase as the pressure increases. As the pressure inside the pipe increases 5-fold, the relative area of the fluidized zone increases approximately 3.5-fold, and the relative height increases 12-fold. By increasing ratio of the cover depth to mean particle size, the relative area and relative height of fluidization increases. New equations were obtained to determine the relative area and the relative height of the fluidized zone.

Study on the Erosion of Choke Valves in High-Pressure, High-Temperature Gas Wells

During the process of gas production in high-pressure, high-temperature (HPHT) gas wells, the choke valve, as the most vital component of the surface control equipment, plays a significant role in regulating the output and reducing the fluid pressure to ensure the safety of surface gathering and transportation equipment. High-pressure, high-velocity fluid flow and solid-phase particles cause deterioration of the choke valve. With the enhancement of intelligent and digital oilfields, conventional choke valves have been progressively replaced by electric choke valves. Due to the complex structure of the throttle valve, the flow path and the velocity state of the fluid in the throttle valve, and the distribution law of the erosion fraction are quite distinctive from those in the ordinary throttle valve, meriting further research. In this paper, a simulation of computational fluid dynamics (CFD) was conducted to determine the effects of the pressure distribution, fluid state, divergent particle sizes, and sand volume on the erosion rate of the choke valve. Under various valve openings, the fluid state and the location of high-risk points can be ascertained. The large particle size (diameter greater than 6 mm) of sand and gravel is convenient for causing concentrated erosion in the position of the valve hole, which induces the channel diameter to expand. Fine silt sand (diameter from 0.1 mm to 1 mm) gives rise to relatively uniform abrasion to the choke’s current-facing surface. This study can optimize the layout of the choke valve and reduce the cost and number of switching wells, thereby decreasing the frequency of maintenance and the pressure fluctuation’s effect on the formation.

The uplift resistance of submarine pipelines buried in medium dense sand

Buried submarine pipelines need to be operated under high temperature and high pressure, and ensuring sufficient buried depth is a necessary factor for safe operation. Based on the plane strain assumption, the purpose of this study is to study the evolutionary mechanism of pipe-soil interaction under the monotonic uplift of buried submarine pipelines through model tests and the Discrete Element Method (DEM) numerical simulation. The results show that the uplift resistance is affected by the embedment ratio and the pipe diameter; during the pipeline uplift process, the development of the uplift resistance is divided into three stages: the development stage, the softening stage, and the residual stabilization stage. The displacement at the peak uplift resistance increases with the increase of the embedment ratio, and the value is about 0.5–1.5%H, and the sand particle size has a great influence on the displacement of the peak uplift resistance and the post-peak softening behavior. According to the comparison of the test results, the prediction model of the load-displacement response of pipe-soil interaction is proposed.

Effects of sand and slurry characteristics on pressure infiltration of bentonite slurry into sand

Two series of experiments were carried out to examine pressurised bentonite slurry infiltration into saturated sand columns. Three types of sand were examined, and water–bentonite and water–bentonite–sand slurries were used in series 1 and 2, respectively. Series 1 investigated the effect of sand particle size and series 2 examined the effect of the fine-sand particle content in the slurry. Scanning electron microscopy (SEM) imaging was used to observe the morphological features of the dry slurry-infiltrated sand samples. A solution for the infiltration distance during mud spurt for water–bentonite–sand slurry infiltration was verified using the data from series 2. The infiltration test results showed that the hydraulic conductivity of the slurry-infiltrated coarse sand for slurry in series 2 was lower than that in series 1. Visual observations and the SEM images showed that sand particles were bound to a bentonite film, indicating that, during infiltration, the channels for fluid flow among the sand particles are blocked by the bentonite particles adhered to the sand particles. The solution for the infiltration distance during mud spurt for water–bentonite–sand slurry infiltration showed good agreement with the experimental results.

Parametric investigation of sand erosion rates in gas pipeline bends under typical industry conditions using simplified method

ABSTRACT The production and transport of sand from oil and gas wells into production and transport facilities results in flow assurance and structural problems. A critical operational issue is the erosion of oil and gas facilities by the suspended sand particles, particularly around flow diversions. This study investigated the effects of four key parameters, namely particle size, sand load, fluid velocity, and fluid density, on the rate of sand erosion in gas pipeline bends using DNV GL-RPO501 and Star CCM+ software package, a Computational Fluid Dynamics (CFD) tool developed by CD – adapco. Sand concentration and particle sizes both cause a linear increase in erosion rate. The particle sizes affected the location of maximum erosion. The single and mixture component gas densities showed an inverse linear and non-uniform relationship with erosion rate. The CFD models underpredicted erosion rates by about 90% compared to the experimental data. An exponential relation exists between the erosion rate and gas/sand velocity especially velocities above 10 m/s. The CFD method largely predicted more realistic values of erosion rate than the DNV GL-RPO501 due to some oversimplified assumptions made in the latter. The CFD tool however compared favorably with the DNV GL-RPO501 at high velocities. Both CFD and DNV GL-RPO501 models are recommended for erosion studies at higher fluid velocities, while the CFD modeling is better at lower velocities by incorporating drag and inertial forces which are important forces at low gas velocities. The particle and fluid velocity affected the sand erosion rate more than the other factors considered. However, future studies should consider modeling erosion rates under transient conditions and investigate the effects of various turbulence models. Different sand mixtures with various particle sizes and other gases such as CO2 should be considered.

Effect of coconut fiber on low-density polyethylene plastic-sand paver blocks

The experimental research object was low-density polyethene (LDPE) waste plastic as a binding material in the production of LDPE bonded sand paver blocks. The LDPE waste plastic was melted in the open air and mixed with sand to form paver blocks. LDPE to sand ratio, percentage of coconut fibers, and sand particle size was varied. The compressive strength, water absorption and density of paver blocks were measured. It was observed that the incorporation of coconut fiber proportion at 3% improved compressive strength by 18.4% and reduced water absorption by 54.1%. The best experimental results were observed at LDPE to sand ratio of 30:70, whereas the finest sand gives the highest compressive strength. The sustainable paver blocks developed in this research can be used in water-clogged areas.

Numerical simulation of cost-effective green high-ductility engineered cementitious composites based on meso-scale particle flow model

To promote the sustainable development of building materials and reduce their cost, the cost-effective green high-ductility engineered cementitious composites (ECC) was developed by using domestic low-cost polyvinyl alcohol (PVA) fibers, ordinary river sand and high-volume incorporation of fly ash (FA) and silica fume (SF). The effects of different river sand particle sizes, sand-binder ratio and water-binder ratio on the bending and tensile properties of ECC were studied. Meanwhile, the meso-scale particle flow model based on discrete element method (DEM) is used to simulate the multi cracking behavior of ECC under four-point bending load and uniaxial tensile load. This is a new application of particle flow model in ECC. Moreover, the distribution characteristics and temporal-spatial evolution law of the of micro-cracks in ECC are simulated by using the DEM. Further on, the distribution of the force chain of the ECC are analyzed, and the visualization of the force chain under bending and tensile load is realized for the first time. Simulation results show that the multi cracking behavior mainly occurs in the pure bending section under four-point bending load, and the micro-cracks under uniaxial tensile load is uniformly distributed on the sample surface. Meanwhile, the unstable fracture of the strong force chain arch is the essential reason for the ECC failure. The curves and failure patterns obtained by simulation is compared to experimental results to verify the effectiveness of the numerical model.

Investigations on methane hydrate formation, dissociation, and viscosity in gas-water-sand system

Understanding the kinetics and viscosity of hydrate slurry in gas-water-sand system is of great significance for the high-efficiency and high-safety development of natural gas hydrates. The effect of micron-sized sands with various concentrations and particle sizes on the hydrate formation, dissociation, and viscosity in gas-water-sand system are investigated in this work. The experimental results show that the hydrate induction time in the sandy system is slightly prolonged compared to the pure gas-water system, and the inhibition effect first strengthens and then weakens as the sand concentration increases from 0 wt% to 5 wt%. Besides, the difference of hydrate formation amount in various cases is not obvious. The concentration and particle size of sand have little effect on the kinetics of hydrate formation. Both promoting and inhibiting effects on hydrate formation have been found in the sandy multiphase fluid. For the viscosity characteristics, there are three variations of hydrate slurry viscosity during the formation process: Steep drop type, S-type and Fluctuation type. Moreover, appropriate sand size is helpful to reduce the randomness of slurry viscosity change. Meanwhile, even at the same hydrate volume fraction, the slurry viscosity in the formation process is significantly higher than that in dissociation process, which needs further research. This work provides further insights of hydrate formation, dissociation, and viscosity in gas-water-sand system, which is of great significance for safe and economic development of natural gas hydrates.

Sintering characteristics of environmentally friendly porous ceramics prepared by self-sintering of desert sand

Natural desert sand has particle shapes and a relatively high content of silica and other useful chemical compositions. Porous quartz ceramics were prepared by self-sintering of three kinds of screened desert sands, and the composition, particle size, phase transformation, microstructure and properties of the ceramics were investigated. Experimental results showed that the particle size of desert sand was dominant in sintering of ceramics and the gradation changed the ratio of silica to feldspar phases, which was increased with an increase in particle size. The low-melting feldspar phases were primary to generate self-sinterability. The obtained ceramics with open, open-closed and closed pores can be prepared from large, medium and small sand particles, respectively.

Effect of sand particle size on interface shear behaviour between bio-cemented sand by MICP treatment and steel structure

This study presents an experimental investigation of the effect of sand particle size on the shear behaviour of bio-cemented sand-steel structure interface, with sand treated by microbially induced calcite precipitation (MICP). Five sand groups were involved with different median particle sizes. The MICP treatment followed the surface percolation method featuring bacterial suspensions with a fixed optical density (linearly related to active cell concentration or urease activity). Scanning electron microscopy was used to identify the microstructure of the samples, while interface shear test was performed to observe the macroscale mechanical behaviour. The testing results indicated that smaller sand particle size was associated with a relatively larger effective calcium carbonate bonding area, providing a more significant bonding effect. Thus, smaller sand particle sizes in the treated samples were associated with higher values for the interface cohesion and a more pronounced increase in the interface friction angle at the peak state (compared to the corresponding untreated samples). By contrast, because the bonding effect broke close to the interface during shearing, the bottom of the treated samples became planar and smooth. Hence, a lower interface friction angle at the ultimate state was identified for a treated sample, compared to the corresponding untreated one.

Experimental Study of the Effect of Backfill Conditions on Soil Responses around a Pipeline under Wave–Current Load

Waves and currents coexist widely in the ocean, and the interaction of waves and currents plays an important role in the instability of submarine pipelines. So far, most studies have concentrated on discussing the dynamic reaction within the seabed around a pipeline under pure wave action, monotypic sediment, and an exposed or fully buried condition. In this study, the effect of current characteristics (e.g., current velocity and propagation direction) and backfilling conditions (e.g., backfill depth and sand property) on the dynamic response around the submarine pipeline is investigated by conducting laboratory experiments. Pipeline was buried in the excavated trench using three types of sand with the median size of 0.150 mm, 0.300 mm and 0.045 mm, respectively. Five relative backfilled depths, with the ratios of backfill depth over the pipeline diameter being 0, 1/2, 1, 3/2 and 2, were tested. The excess pore pressure was measured simultaneously by using the pore pressure sensors installed around the pipeline surface and beneath the pipeline. Results show that both the pore pressure amplitude and its descent rate gradually decrease with an increasing backfill depth, which decreases the soil liquefaction potential. Under the co-current actions, the decrease rate of the pore pressure along the vertical direction increases with an increasing current velocity. However, the increased current velocity leads to a decrease of the attenuation rate under the counter-current actions compared with the pure wave actions, and the counter-current effect on the pore pressure within the seabed is greater than the co-current. The results indicate that the dynamic response around the pipeline in coarse sand is close to that without the backfill scenario, even if the backfill depth reaches up to two times that of the pipeline diameter. It is found that the larger the median particle size of backfill sand, the smaller the impact on pore pressure within the seabed beneath the pipeline.

Effect of Saturation on Shear Behavior and Particle Breakage of Coral Sand

Coral sand is the main filling material for the island–reef foundation. Under tidal actions, the saturation (Sr) of coral sand layers varies with the specific depths in the reclaimed foundation. Studying the Sr effect of coral sand’s mechanical behaviors is crucial for the stability of the reclaimed foundation of island–reefs. In this study, a “quantitative injection method” was designed to prepare coral sand with saturation ranging from 90% to 100%, and unconsolidated–undrained (UU) triaxial shear tests were conducted on coral sand under different effective confining pressures (σ3′). The results indicated that the stress–strain curves of coral sand under various conditions were of the strain-softening type. When σ3′ = 200, 400, 600, and 800 kPa, the shear strength of coral sand decreased exponentially by 13.1, 9.1, 16.8, and 15.2%, respectively, with the increase in Sr from 90% to 100%. As Sr rose, the internal friction angle (φ) dropped by 3.77°. The cohesion (c) was not significantly affected by Sr compared to φ. In consideration of the physical susceptibility of coral sand to breakage, relative breakage ratio (Br) and modified relative breakage index (Br*) were introduced to evaluate the particle breakage behaviors of coral sand samples with different Sr levels in the triaxial shear process. It was found that Br and Br* increase linearly with increasing Sr; the effect of Sr on the particle breakage of coral sand weakens significantly when σ3′ is sufficiently large. The median particle size (d50) of coral sand decreases with increasing Sr, and presents a negative linear correlation with both Br and Br*. Based on comparing the strength and particle breakage characteristics of coral sand samples with varying Sr levels, this study suggests that 92.5% should be considered as the Sr value of coral sand available for testing.

Macro and Mesoscopic Study on the Mechanical Properties of Metakaolin-based Geopolymer Reinforced by Fine Sand

In order to improve the mechanical properties of geopolymer, experimental comparison groups (a) to (f) were set up to explore the influence of particle size and content of fine sand on the unconfined compressive strength of metakaolin-based geopolymers. The results showed that when the particle size of the fine sand decreased, the strength of the geopolymer increased more significantly. When the particle size of the fine sand was less than 0.15 mm and the content was 10% of the maximum mass fraction, the composite possessed the highest strength and reached 41.51 Mpa. The effect of fine sand content on the polymerization process was characterized by SEM. The particle flow software PFC3D was selected to simulate the unconfined compressive process of the specimens, and Fish functions were established to monitor the quantity of cracks, crack distribution status, particle failure mode and porosity changes of the specimens during the unconfined compressive test experiment. The effect of fine sand with different particle sizes and contents on the compressive strength of metakaolin-based geopolymer was revealed from the viewpoint of mesomechanics.

Palaeoclimatic Studies of the Late Quaternary Sediments from Chirakkara, Kollam District, Kerala, India

The Quaternary period is considered one of the most eventful periods of all geologic periods. The present study intends to understand the paleo-environmental conditions that prevailed in the southern part of the Kerala State, India, during the Late Quaternary period. The present study aims to understand the climatic variability of the Holocene epoch in the Chirakkara region, the easternmost part of Polachira wetland, Kollam district, South Kerala, by using granulometric data and geochemical proxies. A core of 2.5 m in length has been collected from the study area, and both textural and TOC/TN analyses were carried out. The variation in grain size is attributed to the variations in the energy level of the transporting medium and turn to the climatic conditions, especially rainfall. The sediments encountered in the core are dominated by sand-sized particles indicating dynamic high energy conditions and high precipitation events. The ternary plot of the sediment samples also suggests violent environmental conditions during the deposition of the sediments. The predominance of low values of TOC/TN ratio found at both ends of the core indicates an autochthonous source for organic carbon, possibly due to the aggravated aquatic phytoplankton activity, and increased lake bioproduction, and/or decline in the delivery of organic matter from the terrestrial environment. High values of the TOC/TN ratio noted at the middle portion of the core at depths from 120 cm to 210 cm indicate the allochthonous source for the organic carbon. Among allochthonous sources, the C3-type plant is dominant, indicating a cool and wet climate. At the same time, the extremely high TOC/TN values at 170 cm core depth indicate a short period of hot and sunny climatic conditions. The analysis of the granulometric data and organic matter proxies suggest that the study area has experienced wet climatic conditions with occasional dry spells during the Late Quaternary Period.

Numerical simulation method of a circulating fluidized bed reactor using a modified MP-PIC solver of OpenFOAM

There are some previous works for simulating a bubbling fluidized bed (BFB) reactor using OpenFOAM's MPPICFoam solver, but those for circulating fluidized bed (CFB) reactors are few. In this study, the MPPICFoam solver was verified with a BFB reactor by comparing the solver's simulation results with the experiment and simulation results from the literature. By introducing the inter-boundary particle circulation function and a new module for setting sand particle size distribution, simulations were performed for a 0.1 MW th pilot-scale CFB combustor under isothermal conditions. The modified solver for the CFB reactor gives similar results as the experiment and commercial computational fluid dynamics (CFD) tool, well-predicting the pressure distribution and solid volume fraction in the riser. • MPPICFoam solver reliability for lab-scale bubbling fluidized-bed reactor verified. • Accurate solver prediction of solid volume fraction (horizontal) distribution. • Model used for numerical simulation to study riser hydrodynamics of a CFB combustor. • Particle size distribution module and new circulating boundary conditions added. • Improved solver shows superior predicted experimental results in dense bed region.

Effect of Particle Character and Calcite Dissolution on the Hydraulic Conductivity and Longevity of Biosand Filters Treating Winery and Other Acidic Effluents

Acidic effluent such as winery wastewater is challenging to remediate. Biological sand reactors can simultaneously remove organics and neutralize winery wastewater via biotic and abiotic mechanisms. The systems have been shown to be suitable for treating the intermittent flow of wastewater at small wineries. It has been shown that dissolution of calcite is the most important abiotic mechanism for increasing the pH of the influent. In this study, sand column experiments were used to determine the effects of (i) sand particle size distribution on calcite dissolution kinetics, and (ii) the effects of calcite particle dissolution on the hydraulic conductivity. The results were then used to calculate the theoretical temporal abiotic neutralization capacity of biological sand reactors with differently sized sand fractions, including unfractionated (raw) sand. The results were compared with those determined from a pilot system treating winery wastewater over a period of 3 years. Sand fractions with larger particles contained lower amounts of calcite (using Ca as a proxy), but exhibited higher hydraulic conductivities (3.0 ± 0.05 %Ca and 2.57 to 2.75 mm·s−1, respectively) than those containing smaller particles and/or raw sand (4.8 ± 0.04 to 6.8 ± 0.03 %Ca and 0.19 to 1.25 mm·s−1, respectively). The theoretical abiotic neutralization capacity of biological sand reactors was compared with a pilot system with the same flow rates, and a temporal abiotic neutralization capacity of 37 years was calculated for biological sand reactors, which compared favorably with the theoretical results obtained for wastewater with pH values between 2 (8.2 years) and 3 (82 years). It was concluded that biological sand filters with around 10% calcite will be able to abiotically neutralize winery wastewater and other wastewaters with similar acidities for the projected life span of the system. Future work should focus on determining the effect of sand grain size on the bioremediation capacity, as well as the use of biological sand reactors for treating other acidic organic wastewaters such as fruit processing, food production and distillery wastewater.

Optimization of long-term fracture conductivity with quartz: An experimental investigation

For the purpose of cost management, many companies and research institutions have carried out technical research on the replacement of ceramic with quartz sand as proppant. However, few studies have systematically carried out short-term and long-term conductivity evaluation experiments for quartz sand proppants with different particle sizes. It is urgent to conduct experiments on the conductivity of quartz sand, and optimize the fracturing design based on the experimental results. The conductivity is the key indicator of the fracturing effect. The greater the conductivity, the better the hydraulic fracturing effect, and the longer the effective period, the higher the fracturing benefit. In this study, by evaluating the long-term conductivity of proppant, the influence of the type of quartz sand proppant, proppant particle size and sand paving concentration on the fracture conductivity are studied. Main results show that 1) the proppant performance of quartz sand produced in Chifeng is better than that of produced in Tongliao; 2) The long-term conductivity experiment results show that the conductivity of quartz sand proppant produced in Chifeng is better than that of TL, and under the same sanding concentration and closing pressure, the larger the particle size of the quartz sand, the higher the conductivity, and the greater the decrease in conductivity with the increase of the closing pressure; 3) In the influence of sand paving concentration, when the sand paving concentration is 5 and 7.5 kg/m2, the conductivity increase with the increase of the sand paving concentration.

Numerical Simulation of Viscosity Effects on Carbon Steel 90° Elbow Erosion due to Sand-Liquid Flow

Elbow pipes are important pipeline components in hydrocarbon transportation systems, and they were prone to erosive wear by the impact of abrasive particles. A discrete phase modeling (DPM) and numerical simulation of the liquid-sand transportation process was carried out focused on the investigation into the influence of carrier fluid viscosity on erosion distribution of carbon steel 90° elbows. The accuracy of the predicted results was validated by comparison with experimental data. CFD simulations have been carried out by combining DPM to predict the erosion rate and particle impaction regions in carbon steel 90° elbow with a diameter of 50.8 mm. The fluid viscosity is set for 1cP, 5cP, and 15 cP with an inlet velocity of 8 m/s, and the size of sand particles is 200 μm. While the maximum erosion rates enhance with an increase in fluid viscosity, the location of maximum particle impaction has been specified to be adjacent to the outlet for 1 cP and 5 cP carrier fluid viscosity. It is also found that increasing the viscosity does not considerably alter the average erosion rate. Moreover, the increase in carrier fluid viscosity with the same flow velocity influences maximum erosion rate and yields 1.45 times higher erosion rates at 15 cP compared to 5cP and 1cP. This is mainly due to severe sand impaction at the side of the elbow wall.