Movement Of Fine Particles Research Articles

The impact of Microbially Induced Calcite Precipitation (MICP) on sand internal erosion resistance: A microfluidic study

Fine particle internal erosion involves the detachment, transport, and deposition of fine particles within soil, significantly impacting agriculture, engineering, and environmental protection. Microbially induced calcite precipitation (MICP) has proven to be an effective method for controlling internal erosion. To optimize MICP protocols for effective erosion control, understanding the microscopic mechanisms by which MICP reduces fine particle erosion is essential but remains unclear. In this study, microfluidic chip experiments were conducted to observe the characteristics of calcium carbonate crystals and fine particles before and after MICP reinforcement and erosion. Through quantitative analysis of the calcium carbonate produced by MICP and eroded fine particles, the effects of bacterial density, concentration of cementation solution, and flow rate on the efficiency of MICP in resisting soil internal erosion were investigated. In addition, three primary mechanisms by which MICP reduces fine particle erosion were identified. Firstly, in situ sand stabilization occurs when calcium carbonate generated by MICP bonds and encapsulates fine particles, forming larger particles that remain stable under erosive flow conditions. Secondly, regional sand stabilization is achieved as MICP-produced calcium carbonate crystals narrow or block the flow channels, preventing extensive migration of fine particles. Lastly, adjacent particle stabilization is facilitated by calcium carbonate crystals, which remain stable during water flow erosion and alter the erosion flow lines, creating zones adjacent to the crystals where fine particle movement is minimized. These findings provide a deeper understanding of the role of MICP in erosion control and can inform the development of more effective erosion mitigation strategies.

Numerical Study of the Movement of Single Fine Particles in Porous Media Based on LBM-DEM

The fine particle liquid–solid flow in porous media is involved in many industrial processes such as oil exploitation, geothermal reinjection and particle filtration. Understanding the migration characteristics of single fine particles in liquid–solid flow in porous media can provide micro-detailed explanations for the fine particle liquid–solid flow in porous media. In this paper, an existing lattice Boltzmann method–discrete element method (LBM-DEM) is improved by introducing a new boundary thickening direct forcing (BTDF) immersed boundary method (IBM) to replace the classical IBM. The new method is used to investigate the migrations of one, two or three fine particles in a flow field in porous media and the reactions of one, two or three fine particles on the flow field. It is found that the movement distance of a fine particle in porous media does not show a linear correlation with the fine particle’s density. A fine particle with a higher density may move a shorter distance and then stagnates. Although a fine particle with a smaller diameter has a better following performance in a flow field, it is also likely to be stranded in a low-infiltration area in porous media. Under the same increase ratio, the increase in the diameter of a fine particle causes an increased pressure drop of the liquid–solid flow. In some cases, the increase in the quantity of fine particles can intensify the disturbance of fine particles on the flow field, improving the movement of fine particles.

Investigating the influence of excitation force on compaction behavior of gravel in granular blends through DEM simulation

During the construction of subgrades, the compaction of granular blends is typically achieved through vibrational techniques at varying the frequencies and excitation forces. This study investigates the impact of excitation forces, within the range of 300-600 kPa, on subgrade compaction by employing the discrete element method (DEM). Calibration tests were conducted to establish the contact parameters for the DEM models, and their reliability was verified via vibration compaction tests. The research further explores the evolution of settlement, particle motion, and contact interactions at both macroscopic and mesoscopic levels as influenced by the excitation forces. Furthermore, the influence of excitation force on the stability of skeleton frameworks was analyzed. The results indicated that the number of contacts in the final state increased consistently with the excitation force, leading to a more uniform distribution. This change contributes to a time-dependent stability within the skeleton framework, which effectively limits the movement of fine particles in the final stages and diminishes the sliding between the coarse particles. Conversely, in the initial phases, a rise in excitation force increases the stress concentration between the contacts, which increases the sliding damage to the skeleton frameworks and leads to greater compaction deformation.

Distribution and movement of fine particles injected in a gas–solid fluidized bed with hydrocarbon liquid spray

In a gas–solid fluidized bed with hydrocarbon liquid spray, a liquid-affected zone (cloudy zone) and a gas–solid zone (non-cloudy zone) coexist. Fine particles with different diameters are injected and shuttle between the two zones to simulate the motion of growing catalyst particles in an industrial fluidized bed reactor. The movement and distribution patterns of the fine particles are investigated via high-speed image and infrared image approaches developed. The probability density based on the coordinates of fine particles reflects clearly the distribution characteristics of fine particles in the bed at different times. Fine particles with smaller diameters are more easily enriched locally during the injection and diffusion process. Moreover, the proportion of fine particles in the cloudy zone to the total fine particles increases with the diameter of fine particles.

The effects of internal erosion on granular soils used in transport embankments

The flooding of embankments used for rail and other infrastructure has the potential to cause lasting weakening of slopes via the movement of fine particles induced by seepage. In laboratory experiments, internal erosion was induced in granular soil samples, with properties consistent with those used to construct transportation embankments, to assess how particle migration through, and out of, samples caused shear wave velocity, strength, stiffness and permeability changes. Shear wave velocity changes, measured using horizontal bender elements, of up to 19 % were observed following fine particle removal of up to 1 % of initial sample mass. Shear wave velocity change was found to be an indicator for identifying the development of permeability change during seepage-induced particle migration. Median measured permeability changes were +5 % and −34 % for samples containing 15 % and 30 % fines, respectively. The largest directly observed permeability and shear wave velocity changes occurred during the initial stages of seepage. Negative correlation was observed between mass of material removed from samples and peak friction angle. Following seepage, soils displayed a dual stiffness behaviour. Stiffness and strength changes were attributed to redistribution of fine particles and opening of pore spaces. Our results have implications for the monitoring of earthworks affected by flooding and seepage as the associated redistribution of fine particles may lead to large changes in slope properties.

Ignition behavior of a mixture of brown coal and biomass during the movement of fine particles in a hot air flow

The combustion of brown coal, biomass and their mixtures was studied experimentally and analytically. The experimental research was conducted using a laboratory setup that reproduced the conditions of combustion of pulverized solid fuel in a boiler furnace. Thermogravimetric analysis was employed as part of the analytical study to determine the key characteristics of combustion of solid fuels, such as temperatures at which the ignition and burnout occur, as well as the combustion index. Scanning electron microscopy was utilized to analyze the surfaces of coal and wood particles to detect pores, cracks and channels. To determine the tendency of the solid fuel mixture to slag heat exchangers in boiler furnaces, the ash residue characteristics (iron oxide deposits, active alkali, calcium sulfate compounds) were obtained. Biomass is more reactive than brown coal. Its ignition delay times at 500 °C and 750 °C are 57 % and 25 % lower, respectively, than those for coal. The higher the biomass content in the solid fuel mixture, the lower the ignition delay time. The heating source temperature at which the coal/biomass fuel mixture ignites corresponds to the temperature at which biomass ignites. With a larger proportion of biomass, the temperature during the fuel mixture combustion goes down, while the combustion index increases. On the basis of the findings of the conducted research, optimal proportions of solid fuel components were found (80 % brown coal, 20 % biomass). Also, fuel preparation and feeding systems for pulverized fuel combustion and fluidized bed combustion of optimal fuel mixtures in a coal-fired boiler furnace were proposed.

Soil processes in the Aeolian Litoral Sheet of Doñana National Park (Huelva, SW Spain): the catena of Colón small-lake ecosystem

The wetlands on the quartz sands aeolian sheet make up one of the ecosystems most recognized and important of the Doñana National Park and Doñana Biological Reserve (South Spain). More than 650 temporal small-lakes have been surveyed in the abundant sand depressions of the aeolian sheet, the most are a hydro-geomorphological dune-small-lake system. This paper studies the pedological processes around Colón small-lake ecosystem wetland (COL), one of the more interesting temporal small-lakes. The movement of fine particles through sand dunes ("sand washing") and their subsequent accumulation in depth is the process responsible for the formation of a large part of the small and medium small-lakes in the Eolian Litoral Sheet of Doñana. Their bodies of water are supported by these clay layers generated corresponding sometimes to ancient soil horizons formed under previous different ecological conditions. The vegetation, the soil morphology and the evolution of the physical-chemical processes studied in this geosystem small-lake of Colón allow understand this phenomenon of chronologies very recent.

Computer vision-aided DEM study on the compaction characteristics of graded subgrade filler considering realistic coarse particle shapes

The compaction quality of subgrade filler strongly affects subgrade settlement. The main objective of this research is to analyze the macro- and micro-mechanical compaction characteristics of subgrade filler based on the real shape of coarse particles. First, an improved Viola–Jones algorithm is employed to establish a digitalized 2D particle database for coarse particle shape evaluation and discrete modeling purposes of subgrade filler. Shape indexes of 2D subgrade filler are then computed and statistically analyzed. Finally, numerical simulations are performed to quantitatively investigate the effects of the aspect ratio (AR) and interparticle friction coefficient (μ) on the macro- and micro-mechanical compaction characteristics of subgrade filler based on the discrete element method (DEM). The results show that with the increasing AR, the coarse particles are narrower, leading to the increasing movement of fine particles during compaction, which indicates that it is difficult for slender coarse particles to inhibit the migration of fine particles. Moreover, the average displacement of particles is strongly influenced by the AR, indicating that their occlusion under power relies on particle shapes. The displacement and velocity of fine particles are much greater than those of the coarse particles, which shows that compaction is primarily a migration of fine particles. Under the cyclic load, the interparticle friction coefficient μ has little effect on the internal structure of the sample; under the quasi-static loads, however, the increase in μ will lead to a significant increase in the porosity of the sample. This study could not only provide a novel approach to investigate the compaction mechanism but also establish a new theoretical basis for the evaluation of intelligent subgrade compaction.

Effect of Gradation Characteristics and Particle Morphology on Internal Erosion of Sandy Gravels: A Large-Scale Experimental Study

Internal erosion refers to the seepage-induced fine particle migration phenomenon in soil. Deep alluviums in valleys usually contain cohesionless gap-graded sandy gravels with poor internal stability. The construction of embankment dams on such alluviums could pose a high risk of internal erosion. This study systematically investigated the internal erosion of cohesionless gap-graded sandy gravels with an emphasis on the effects of gradation characteristics and particle morphology. A series of large-scale internal erosion tests were conducted on gap-graded sandy gravels with different gap ratios, fines contents, and coarse particle morphologies under the surcharge pressure of 1 MPa. The internal erosion characteristics, including soil permeability, eroded soil mass, and soil deformation during the erosion process were comparatively analyzed in combination with a meso-mechanism interpretation. The results show that the increase of the gap ratio can reduce the internal stability of soil and promote the mechanical instability. Fines content affected the permeability and internal stability of soil by altering the filling state of inter-granular pores and the constraints on fine particles. Coarse particles with higher roundness, sphericity, and smoothness can facilitate the movement of fine particles and promote the mechanical instability of the soil matrix.

Evaluation of the impact of the intensive exploitation of groundwater and the mega-drought based on the hydrochemical and isotopic composition of the waters of the Chacabuco-Polpaico basin in central Chile

A hydrogeochemical and isotopic study has been carried out to understand the hydrogeological functioning of a small alluvial aquifer in central Chile in a context of mega-drought and intensive exploitation of its waters. Additionally, two mine tailings dams from porphyry copper mining are situated in the area. The prolonged mega-drought, which has lasted for over thirteen years, has resulted in a significant decrease in rainfall recharge and a drop of up to 50 m in piezometric levels, although no serious groundwater contamination problems have yet been detected, except for a rise in nitrate contents (ranging between 23 and 45 mg/L NO3) attributed to return irrigation. Groundwaters are calcium-bicarbonate and calcium-sodium-bicarbonate in composition. The values of δ18O and δ2H of the alluvial aquifer indicate fractionation by evaporation that would be explained by the recirculation of water that occurs in the agricultural areas of the basin, where the excess irrigation water that go back to the aquifer presents fractionation by evaporation. The δ34S and δ18O of dissolved sulfate point to pyrite oxidation, which could be related to the pyrite present in the copper porphyry and recognized in the Andes Cordillera. The 87Sr/86Sr isotopic values of the alluvial aquifer waters are close to the isotopic fingerprint of the volcanic rocks of the Abanico Formation. However, the water from the wells located further downstream in the basin and close to the tailing dams show δ34S and δ18O of dissolved sulfate and 87Sr/86Sr consistent with Miocene intrusive mineralogies of the copper porphyry type. The groundwater chemistry does not show water seepage from the tailings dam. Therefore, a minor contribution of minerals related to the intrusive rocks is proposed, which would originate from the movement of fine particles by the wind from the dams to the valley floor. The 14C activities indicate that groundwater is recent.

Numerical study on the effect of airflow on powder mixing in a container blender

Powder mixing is critical in many industries. Despite the wide variety of available mixers, the container blender is favored in industries due to easy manufacturing and convenient operation. As fine powders are frequently encountered in practical mixing, the presence of air during mixing may significantly impact the process. However, a scientific understanding of air–particle interactions in powder mixing has not been established so far. From a physical view, the air drag force on particles might be significant when the gas velocity is high and the particles are fine. Therefore, this novel study numerically investigates the effects of particle size and air presence on powder mixing under typical conditions, such that the relationship between particle–fluid dynamics and mixing performance is clarified for the first time. In the calculation, our advanced computational fluid dynamics–discrete element method, namely, the flexible Eulerian–Lagrangian method with an implicit algorithm, is utilized. To examine the effect of particle size on powder mixing, the coarse-grained discrete element method is employed for fine particle systems. Through the advanced numerical framework, the effect of airflow on powder mixing can be discussed in depth. The numerical results show that airflow accelerates the mixing of fine particles under the investigated rotation speeds. Based on the calculation results of the particle kinetics and fluid velocity distribution, it is clarified that the accelerated mixing results from the fine particle movement under air entrainment. How the movement of fine particles is developed is also elucidated by the continuously circulating gas flow and fluid drag force. Thus, this study provides a new understanding of the effects of airflow on powder mixing, which has not been scientifically clarified in previous studies.

EXPERIMENTAL STUDY OF THE INTERNAL EROSION BEHAVIORS OF GRANULAR SOILS IN HORIZONTAL SEEPAGE

Internal erosion is one of the most common failure mechanisms in hydraulic structures. The internal erosion is generally initiated by horizontal seepage in earth-filled embankments such as levees. With a newly developed apparatus we carried out a set of internal erosion experiments in horizontal seepage. The experiments used gap-graded granular soil to prepare the specimens. The experimental results revealed that, in a horizontal column, the upper part of the specimen is preferentially eroded, sequentially forming a dominant seepage area. When the erosion progresses, the dominant seepage area gradually expands from the upper part to the lower part of the column. At the particle scale, the localized fine-particle movement can be observed in the erosion process when the hydraulic gradient is relatively small, e.g., less than 0.62. During the early stage of erosion, the particles are rapidly eroded. With the erosion time increasing, the particle loss slows down and even ceases if there is sufficient time.

Factors affecting geotextile filter long-term behaviour and their relevance in design

Geotextile and granular filters are widely used in civil (e.g. earth dams, embankments, drainage trenches, etc.) and environmental (e.g. landfills, permeable reactive barriers, etc.) engineering works. Geotextile filters are considered to be an effective alternative to conventional granular filters whose function is to prevent the movement of fine particles from the base soil allowing the liquid to flow as freely as possible. The design of a geotextile filter requires the knowledge of the base soil–filter interaction that is a very complex process due to the large number of factors involved. In this paper, the complex cases of geotextile filter design in contact with internally unstable cohesionless soils and in critical/severe applications are analysed based on recent research also developed by the authors. Moreover, the influence of the main factors affecting geotextile/filter long-term behaviour which are generally neglected in current design criteria, such as vertical effective stress, partial clogging, flow conditions, type of contact at the interface and type of permeant, are examined. Furthermore, various performance tests to evaluate the long-term soil–geotextile filter behaviour and the reliability and limits of different design criteria for cohesionless soils are discussed.

INVESTIGATION OF THE EFFECT OF SEAWATER INJECTION ON OIL DISPLACEMENT FROM CARBONATE ROCK (ON THE EXAMPLE OF A FIELD IN KAZAKHSTAN)

Increasing oil recovery is one of the most pressing issues today. Since the last century, scientists have been actively researching to enhance oil recovery. A huge number of scientists have turned their attention to this issue by using low-mineralized water (LMW). Thus, since the 90s, both theoretical and experimental research has been actively studied. Increased oil recovery depends on rock wettability and surface tension. This approach was key to a significant amount of experimental work. But, despite a lot of research, scientists still have not come to a consensus on the mechanisms that contribute to increased oil recovery. One of the main mechanisms is considered to be the movement of fine particles (i.e., clay particles) during flooding with low-mineralized water (LMW). As shown by the study of the topic of LMW, experimental work was often carried out on light oil. Experimental work with light oil has been positive. However, the interaction of the LMW with high-viscosity oil has not been deeply studied, which is relevant to the fields of Kazakhstan.

Effect of Fine Particles and Soil Heterogeneity on the Initiation of Suffusion

Hydraulic backfill structures can be affected by internal erosion, which develops if 2 conditions are met: detachment and migration of particles due to hydraulic seepage. Suffusible soils involve an easy movement of fine particles within the matrix, and this process depends on the particle size distribution of the soil and hydraulic load. If suffusion in homogeneous soils has been widely studied, it has rarely been approached in heterogeneous soils. Cohesionless soils can involve many heterogeneities, due to gap grading or segregation, which can be a cause of internal erosion under severe seepage. In this study, attempts are made to evaluate the influence of fine particles type, rate and distribution of heterogeneity on the onset and development of suffusion. This process is investigated by using a soil sample within a column, submitted to a horizontal unidirectional flow. Different types of fines (kaolinite, illite, silt) and three configurations (central, downstream, and distributed) involving different rates are used by the introduction of coarse sand into a mixture of fine sand and fine particles. Two heterogeneity rates of 20% (weak heterogeneity) and 60% (high heterogeneity) were used and the results were matched with those obtained on the homogeneous soil. The results show that among the fine particles tested with the same configuration and heterogeneity rate, illite provides the highest resistance to suffusion. In addition, suffusion increases with the heterogeneity rate above a given threshold value. These results help us to assess a better understanding of the effect of heterogeneities on the transport and retention mechanisms of fines in granular soils.

Physical and numerical modelling of drainage and consolidation of tailings near a vertical waste rock inclusion

The use of waste rock inclusions in tailings impoundments is a recent technique that offers many advantages, but it also raises a few technical issues that must be addressed to optimize their design. A laboratory physical modelling study was conducted to assess the effect of waste rock inclusion on the behavior of initially saturated hard rock mine tailings in terms of drainage and consolidation. The evolution of pore-water pressures and settlements after hydraulic deposition of the fine-grained tailings (slurry), with and without a drainage inclusion, has been monitored and analysed. This investigation also focused on the evolution of the tailings void ratio and volumetric water content, the amount of water transferred to the waste rock, and the movement of fine particles at the interface between the two materials. The experimental results are used to demonstrate how such waste rock inclusion can affect tailings consolidation by reducing pore-water pressures with accelerated water drainage, for various imposed conditions. The experimental data are also analysed with numerical models to better understand the coupled processes involved. A discussion follows on practical implications of the use of waste rock inclusions in tailings impoundments.

Identifying the position of the compacted layer by measuring soil penetration resistance in a dryland farming region in Northeast China

AbstractTopsoil is disturbed by ploughing, the effects of infiltration, the movement of fine particles from the topsoil to the subsoil, and direct pressure from agriculture machinery, all creating an abrupt delineation in the form of a compacted layer with very low permeability. Spatial variability of soil properties, such as soil structure and penetration resistance (PR), can help identify the compacted layer. However, there are no quantitative methods to describe this layer. In this study,PRwas used to survey different soil types. A Mann–Kendall (M‐K) test ofPRdata was used to identify the presence and position of the compacted layer in a dryland farming region of Northeast China. Our results demonstrated thatPRwas mainly affected by bulk density and soil water content. Compared with the topsoil,PRwas more significantly affected by water content in deeper soil layers. An M‐K test of thePRcurve can provide a more reliable and objective assessment of the thickness of the plough layer and location of the compacted layer than field observation. Our data indicated that there was a compacted layer in the soil profile in the study areas and the spatial variability of the compacted layer was heterogeneous. The plough layer was shallow, and the compacted layer was thicker in areas with frequent use of agricultural machinery. Moreover, frequent use of agricultural machinery resulted in aPRof the plough and compacted layers that was greater than that in other areas. Information on identifying the position and thickness of the compacted layer and the factors influencing their spatial distribution can be used to create effective soil management options and improve conditions for the development of plant roots in dryland farming regions.

The Role of Flow Rate and Fluid Alkalanity on Fine Particles Movement and Influencing the Petrophysical Properties of Reservoir Sandstone

Permeability decline related with fine migration is one of the most widespread phenomenon that occurs in most oil reservoirs. Fine migration is intensive in sandstone reservoir, but frequently misinterpreted. Movement of fine particles might be problamatic to identify and even not easy to predict and interpret. The main goal of this study is to investigate the influence of flow rate and fluid alakalinity on petrophysical properties of selected reservoir sandstone. To determine the types of clay minerals with calculating the percentage of each types and the shape, position, and distribution within the rock matrix, first selected core samples were examined by X-ray diffraction and scanning electron microscopy. This is also to identify the bulk mineralogy and clay fraction.. The result of this study shows that higher alakalinity fluid flow through reservoir standtone might cause a significant reduction on permeability. While at low pH fluid, the degree of damage is less damage than high pH value. However, the reduction on permeability was estimated by conducting a series of core flood experiments by injecting alkaline solution (pH 9 and pH 11) with stepwise increasing flow rate (50, 100, 200 ml/ h). Furthermore, the basic petrophysical properties of such porosity and initial permability were measured prior to testing. Ultimately, a series of core flooding were also conducted to investigate the influence of clay mineral content, pH and flow rate on sandtone reservoir permeability. High pH solutions significant permeability reductions were recorded, during the flood of pH 11 alkaline solution reductions as high as 36- 50-% were obtained while, the degree of damage was observed less severe with (pH9). Hence, the magnitude of damage was more severe with high flow rate and higher pH. The result shows that the clay minerals present in the cores were characteristics to fine migration thus causing negative impact on reservoir characteristics.

Numerical investigation on urea particle removal in a spray scrubber using particle capture theory

The effective removal of particulate matters from the flue gas emitted from Urea Prilling Tower is very essential to conform to the environmental standards. Based on particle capture theory, the user-defined-function (UDF) codes were written to implement the simulation of particle removal. A novel numerical simulation method is carried out to study the flow field and the effects of gas-phase loading factor, spray density, particle size and droplet size on the particles removal efficiency. The results show that the removal efficiency of particles above 10 μm can reach 97%. But the removal efficiency of particles less than 10 μm deteriorates with decreasing particle diameter due to the randomness of a fine particle movement. In addition, the improved empirical correlations of the removal efficiency were obtained based on numerical simulation, which provides the guidance for optimum design of a spray scrubber in practical engineering applications.

Study on the movement and deposition of particles in supercritical water

The movement and deposition of fine particles in supercritical water is closely related to the safe operation of supercritical water reactors and supercritical thermal power units. When deposition of corrosion particles occurs, it will affect the heat exchange of the pipe wall and cause the wall temperature to rise rapidly. It will seriously threaten the safe and stable operation of supercritical water reactors or supercritical thermal power units. In this paper, the ANASYS numerical software was used to simulate the movement of fine particles in supercritical water. The effects of parameters such as heating power, inlet temperature, inlet velocity, average particle diameter, and asymmetry of heating on the influence of fine particles in the supercritical water were investigated. The results show that with the increase of inlet temperature, the peak value of particle deposition concentration gradually approaches the inlet section of the pipe. With the increase of inlet velocity, the peak value of particle concentration gradually moves to the outlet of the pipe. The heating of the pipe has a certain inhibitory effect on the concentration and deposition of particles. The simulation result of the particles deposition has been compared and verification with the existing experimental data. The verification results show that the particle deposition concentration distribution characteristics obtained by the simulation and the experimental data are consistent. It facilitates the mechanism analysis of the movement and deposition characteristics of the fine particles in the supercritical water. It is conducive to the safe design of supercritical water reactors.