Sand Particle Size Research Articles

Experimental study of frictional resistance influences on tunnel face stability

In recent years, there have been several ground surface collapses due to tunnel excavation in Japan. Although such accident is caused by ground loosening and tunnel face collapses due to excavation, there is no accepted theory for estimating the face stability because this phenomenon is quite complicated and highly influenced by the supports and lining types. Specifically, the loosened area is relatively large for the urban NATM method, which applied in a shallow sedimentary rock layer. Therefore, a method to quantitatively evaluate the tunnel face stability by this kind of mechanical property is essential. In this study, 2D tunnel pull-out test was conducted to observe the influence of frictional resistance on tunnel face failure and loosening area by changing the shear resistance angle using three particle sizes of dry silica sand and different variation of earth covering. The result demonstrated that failure region doesn’t reach the ground surface when the shear resistance angle is 46.4° and covering thickness to tunnel height ratio H/D is over 5 or the angle is 55.8° and H/D is over 3. This study considered that there is an arch effect depending on frictional resistance and earth coverings occurred. Furthermore, even with the same earth covering, the smaller the shear resistance is, the earlier the ground surface collapses. Therefore, it could be said that the higher the frictional resistance is, the later the collapse proceeds.

Study the Affecting Factors on Free overfall Flow and Bed Roughness in Semi-Circular Channels by Artificial Neural Network

One of the significant problems facing the water resource engineer is calculating the coefficient of roughness for subsequent design calculations of the discharge amount of a channel or river. In this study, experiments were conducted in a semi-circular, straight channel to investigate the factors affecting bed roughness and flow discharge using Artificial Neural Network (ANN). For this purpose, three semi-circular channel models with free overfall were constructed and installed in a 6-meter-long laboratory flume. The length of these models was 2.50 m with three different diameters (D= 150, 187, and 237mm) and three bed slopes (S=0.004, 0.008, and 0.012). Three sand particle sizes (ds) were used for each semi-circular channel to roughen the bed. The results showed that the Manning roughness coefficient obtained using a rough bed surface was higher than the channel with a smooth bed surface. Also, the results revealed that the Manning roughness coefficient and the Froude number were inversely related. (ANN) analysis showed a good agreement between the experimental and predicted results of flow and roughness. The bring depth (yb) had an 85.8% impact percentage on the free overfall discharge for semi-circular channels, while the bottom slope (S) had only 1.1%.

Preliminary investigation on effects of size, polymer type, and surface behaviour on the vertical mobility of microplastics in a porous media

Due to the ubiquitous nature of microplastic (MP), knowledge of its fate and migration in subsurface environments like soil becomes extremely important to understand underlying ecological risk. The fate and migration of MP in subterranean settings like sand are governed by the retention/transport properties influenced by the interaction of sand and MPs. In this study, sand column experiments under simulated rainfall conditions were conducted for 180 days to assess the vertical migration of mixed MPs consisting of polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET). Sand column experiments were subjected to 60 wet-dry cycles over 180 days. The effects of polymer type, microplastic size, sand particle size, and surface roughness on the migration of MPs were evaluated. Results showed that the smallest-sized fragmented PE particles had the highest migration potential compared to PET and PE. The ratios of the diameters of MP particles and sand particles (dMP/dsand) played a significant role in determining the penetration depth of the various sizes of MPs. The MP particles with dMP/dsand 0.11 showed greater penetration depth in sand media and were detected in the column effluent water after 60 days of a column run. In addition, surface roughness, low ionic strength water, irregularly shaped particles, and wet and dry cycles contributed to the migration of MPs in the sand column. Three new absorbance peaks corresponding to the hydroxyl, CO stretch, and carbonyl groups evolved in the extracted PE MPs sample from different depths, as shown by FTIR analysis, suggesting that PE MPs had been oxidised. XPS analysis revealed changes in the surface properties of the MPs, indicating that oxidation occurred at the top layer, causing structural deterioration of the PE MPs. However, oxidation of the surface bonds was restricted in the layers underneath due to a lack of oxygen. The finding of the study suggests that in a natural environment, such accumulation and migration of MPs in sandy soil can increase the possibilities to the underlying groundwater contamination.

Removal of chlorine, microparticles and water from high-viscosity liquids by a sand filter coupling hydrocyclone

Separation energy consumption in industrial production accounts for 10–15 % of global energy consumption. Nonthermal separation represented by sand filtration can open a new door to separation energy savings. Traditional sand filters cannot be regenerated completely, which limits their efficiency. A sand filter coupling hydrocyclone (SFCH) was proposed to enhance regeneration. The performance of SFCHs with different separation particle sizes was systematically analyzed, as indicated by turbidity, water, and chlorine in a pilot-scale experiment. The larger the sand particle size of the SFCH was, the longer it took to reach saturation. The efficiency and cycle were balanced by combining SFCHs with particle sizes of 1–2 mm and 0.5–1 mm. The average turbidity, water and chlorine decreased from 793 NTU, 1439 mg/L, and 126 mg/L to 155 NTU, 389 mg/L, and 88 mg/L, respectively, with a cycle of 88 h. Under the same conditions, the effluent turbidity of the SFCH was half of that of the original disc centrifuge, which indicates that the life of the downstream alumina bed was doubled. Almost 260 t/year alumina consumption can be reduced in a 200,000 tons/year-capacity petroleum resin plant, saving 600,000 USD/year, mainly due to the extension of the service life of the alumina bed.

Experimental study of the critical sand starting velocity of gas-water-sand flow in an inclined pipe

The purpose of this paper is to study the critical sand starting velocity and transformation law of flow pattern based on gas–water–sand three-phase flow in an inclined pipe. Firstly, the indoor simulation experiment system of gas–water–sand three-phase flow was used to test the conversion law of flow pattern based upon the different gas void fraction. Secondly, the influence of slug bubbles on sand migration was investigated according to distinctive hole deviation angles, gas void fraction and sand concentration. Finally, the critical sand starting velocity was tested based on dissimilar hole deviation angles, gas void fraction, sand concentration and sand particle size, and then the influence of the above-mentioned key parameters on the sand starting velocity was debated based on the force analysis of the sand particles. The experimental results illustrated that when the gas void fraction was less than 5%, it was bubbly flow. When it increased from 5% to 30%, the bubbly flow and slug flow coexisted. When it was between 30% and 50%, the slug flow and agitated flow coexisted. When it reached 50%, it was agitated flow. Providing that the hole deviation angle was 90°, the phenomenon of overall migration and wave-like migration on the surface of sand bed was observed. On the contrary, the phenomenon of rolling and jumping migration was recognized. The critical sand starting velocity was positively correlated with the hole deviation angle and sand particle size, but negatively associated with the gas void fraction and sand concentration. This research can provide a certain reference for sand-starting production in the field of petroleum engineering.

Experimental Investigation for Free Overfall of Flow in Semi-circular Channels

In the present paper, the effects of diameter, bed slopes, and bed roughness on free overfall flow of semi-circular channels were investigated experimentally. For this purpose, three models of semi-circular channels with free overfall were built and installed in a 6m long laboratory flume. These three models were 250 cm long and had varying diameters 160, 200, and 250 mm. Four different bed slopes (S) were used in each of these models (0, 0.004, 0.008, and 0.012). For each bed slope, three sand particle sizes were used to roughen the bed (1.18mm, 2.36mm, and 4.75mm). For each model, the experimental testing program contained sixteen series of experiments. They were divided into two categories: four smooth beds and twelve rough beds. Different rates of discharge (Q) were examined in a total of 192 tests. According to the experimental results of all models, the Froude number (F r ) of flow decreases as the end depth ratio ( y b / y c ) increases for various bed roughnesses. For varying bed slopes and bottom roughness, a simple linear formula was developed to relate the brink depth ( y b ) with the critical depth ( y c ). For various bed slopes and roughness conditions, simple empirical equations for the flow over the free overfall in semi-circular channels were found. The results demonstrate a good level of agreement.

In depth review of the ecology of arenicolous marine fungi

As an ecotone, sandy beaches exist within a multi-dimensional mesh of environmental gradients, shaped by numerous parameters (e.g. temperature, humidity, wave action, sand particle size and salinity). These limit the proliferation of a narrow group of fungal species. Obligate arenicolous marine fungi are an ecological assemblage of sand-associated heterotrophs that inhabit sandy beaches. These organisms have evolved to cope with dynamic beach conditions, having a cosmopolitan distribution across tropical, subtropical and temperate regions. Herein we provide an overview of published works relating to the fungi of sandy beaches, focusing on the past half-century. We outline a broad range of topics in ecology including fungal adaptive traits to intertidal conditions at the morphological and genetic levels, temporal and spatial patterns in community structure, and species variations in substrate preference. Collectively, these concepts should encourage marine mycologists to embrace a holistic set of perspectives to shape the outlook for beach ecology.

Optimization of Red Sand Particle Size and Composition in Mixture with Ordinary Sand to Enhance Concrete Quality

Abstract In this study we determined the effect of variations in composition and particle size of Red Sand (RS) grains on the quality of concrete. Concrete was prepared as cubes of 15 cm3 with a composition of cement, sand and gravel in a ratio 1:2:3 and water to cement ratio of 0.5. Variations of RS (fine aggregate) composition are 0 %, 5 %, 10 %, 15 %, 20 % of the weight and red sand grain particle size were prepared as 80 mesh, 100 mesh, 120 mesh. Mechanical properties of the maximum concrete pressure strength test at a composition of 5 % along with a decrease in the size of the red sand grain size of 100 mesh and 120 mesh RS 100-5 and RS 120-5 with pressure forces of 35.4 MPa, and 35.5 MPa, respectively. On the other hand, the red sand with 80 mesh grain size have maximum pressure force in a composition 10 % RS 80-10 is 34.6 MPa. It is considered the addition of red sand fine aggregate has an impact on improving the quality of concrete.

Application of superabsorbent geotextiles to decontaminate and improve crude oil-contaminated soil

The contamination of soil by various oil products is a severe geo-environmental problem. In this study, some geotextiles were used as superabsorbent geotextiles to decontaminate soil polluted with crude oil. The ability of these geotextiles to absorb oil is better than that of absorbing water. The removal efficiency of the absorbent geotextile was first evaluated by placing the spacer fabrics in different arrangements in contaminated soil samples. Second, the shear strengths of the decontaminated soil samples were evaluated through a series of direct shear tests and compared with those of contaminated soil. The effects of crude oil content, vertical stress, and geotextile arrangement were thoroughly investigated to understand the vivid behavior of the specimen matrix. The results showed that the geometric properties of geotextile and sand, such as the mean size of sand particles, aperture size, fluffs, and piles of geotextile, geotextile roughness, and the two phases occurring in the specimens – wettability and saturation of absorbent layer – are vital in determining the sand-geotextile interface and the behavior of shear strength parameters of the matrix. Ultimately, the results confirmed the efficiency of absorbent geotextile as a potential method for controlling soil contamination and improving the shear strength parameters.

Particle characterization using optical measurements and neural networks

We present a novel optical particle sensor technique using artificial neural networks. This method relies on observations of light scattering and extinction by particles as input features to a trained neural network, which provides relevant particle distribution and representative shape for an integrated particle mass flow estimation. The models are trained on artificial data, generated for particles that the sensor is likely to encounter. The feasibility of our method is demonstrated through an experimental measurement of solid sand particles injected into a high-speed wind tunnel. The results show accurate estimations of the injected sand mass flow and particle size statistics, with a sand mass flow root-mean-square error of 0.28 g min−1 or 4.1 from the monitored rate using a precision scale. This measurement framework paves the way for sensor applications in harsh operating environments with limited optical access.

Biocementation of coral sand under seawater environment and an improved three-stage biogrouting approach

The Sporosarcina pasteurii (S. pasteurii)-DSM 33 was acclimated to grow and secrete urease under different salinity level conditions via direct evolution method, and ultimately the new acclimated species, S. pasteurii-DSM 33-ASW100, was of higher cell growth rate and ureolysis activity under seawater environment. Meanwhile, this study further revealed a fact that high concentration of calcium chloride (>0.25 mol/L) would inhibit the existing urease activity but hardly affect the urease secretion function of S. pasteurii-DSM 33-ASW100. The rising of urea concentration would not mitigate the inhibitory effect of calcium chloride on urease activity; by contrast, it could stimulate S. pasteurii-DSM 33-ASW100 to secrete more urease, ultimately conducting the microbially induced carbonate precipitation (MICP) reaction under a higher pH level (∼8.0). In the seawater environment, the optimal coral sand particle size for MICP reaction was about 0.5–1.0 mm. Moreover, the new designed three-stage biogrouting method significantly mitigate the issue of non-uniform distribution of cells and crystals in the column, thereby greatly increasing the unconfined compressive strength of MICP-treated coral sand column (>9.0 MPa) with a relatively high CaCO3 content (∼32 % by weight) as well as calcium ion utilization rate (∼85 %). Results also indicated that excessive input of CaCl2 (>0.5 mol/L) may result in less uniformity of crystallization and thus lead to a relative lower unconfined compressive strength (∼4.0 MPa). Excessive addition of urea (>1.0 mol/L) may lead to partial clogging issues due to too fast reaction of MICP, consequently column strength dropping down to around 2.0 MPa.

Image Segmentation Method on Quartz Particle-Size Detection by Deep Learning Networks

In the beneficiation of quartz sand, hydraulic classification is a primary way to obtain quartz production in various size fractions. It is essential for plants to measure the particle size of quartz sand during the classification, in time to evaluate the classification efficiency. However, the traditional manual-screening method consumes labor and time, while the particle-size analyzer is expensive. Thus, a size-detection method of quartz-sand particle is proposed in this paper, which is based on a deep learning semantic-segmentation network Fully Convolutional Networks (FCN)-ResNet50. The FCN-ResNet50 network sand segments images, and the average particle size of quartz sand is obtained after converting the pixel-particle size to physical-particle size. Using deep learning, the quartz sand with particle sizes of −40 + 70 (0.212–0.38 mm), −70 + 100 (0.15–0.212 mm), −100 + 140 (0.109–0.15 mm), and −140 + 400 (0.038–0.109 mm) meshes, can be measured directly. The results showed that the validation accuracy of the FCN-ResNet50 was over 97%, and the loss value was approximately 0.2. Compared with the UNet-Mobile and Deeplab-Xception, the average error of particle-size detection was approximately 0.01 mm, which was close to the manual calibration-software results. This method has the advantages of quick sampling and low equipment costs, increasing the hydraulic-classification efficiency of quartz sand and promoting automation in the concentrator.

Coarse-grained CFD-DEM simulation of coal and biomass co-gasification process in a fluidized bed reactor: Effects of particle size distribution and operating pressure

The co-gasification of coal and biomass through fluidized bed gasifier is a promising technology for the improvement of the utilization efficiency of fossil fuels and the development of renewable energy. In this work, a coarse-grained computational fluid dynamics-discrete element method (CFD-DEM) simulation is performed to investigate the co-gasification process in a bubbling fluidized bed gasifier. The effects of particle size distribution and operating pressure on the hydrodynamics, heat transfer, and co-gasification performance are analyzed. The results show that the increase of sand particle size distribution (PSD) width slightly affects the particle concentration distribution, particle residence time distribution, and co-gasification performance. The heat transfer rate of convection is an order of magnitude higher than those of conduction and radiation. At higher PSD width, the formation of the vertical solid temperature gradient at the bed bottom is attributed to the deteriorated solid mixing. As the operating pressure increases, the bed temperature decreases apparently. In addition, the variation of the convective heat transfer rate dominates the heat transfer efficiency as the operating pressure changes. The application of elevated operating pressure benefits to the thermal-chemical conversion of blend fuel since the char conversion reaction is accelerated.

Performance Comparison of Different Particle Size Distribution Models in the Prediction of Soil Particle Size Characteristics

Particle size distribution (PSD) is a rich source of information about soil properties, including soil gradation and soil particle size characteristics. This paper compared the PSD prediction ability of three types of mathematical model. We selected nine models that have been proven to accurately predict sample points in previous studies, and we fit 144 pieces of experimental data on 12 texture classes of soil samples from the UNSODA database. We compared the models’ capability for predicting non-sample points, which is important for predicting soil particle size characteristics. Each model’s ability to predict non-sample points of different texture classes of soil was studied using a comprehensive ranking method. The relative differences in the models’ prediction of non-sample points of different texture classes of soil were analyzed using the relative error method. The results showed no considerable correlation between the number of model parameters and the prediction accuracy. For the various texture classes of soil, the Skaggs model and Weipeng model had the highest accuracy in predicting non-sample points, and the Skaggs model had the widest range of application. The Zhongling model and the Weibull model were better in predicting only one texture class of soil, respectively. The Fredlund model, Kolve model, Rosin model, Van Genuchten model and Best model were not as successful as other models. The Weipeng model overestimated the solid particle mass proportion, while the Skaggs model underestimated it when the clay particle content was greater than 20%. Both the Weipeng model and the Skaggs model demonstrated good prediction accuracy when the particle size was within the silt particle size range. The Skaggs model overestimated the particle mass proportion, while the Weipeng model underestimated it when the particle size was within the sand particle size range.

An experimental study on hydrodynamic process, beach profile, and sand migration in swash zone under action of dam-break bore

This study makes an experimental study on hydrodynamics and sediment driven by dam-break waves in swash zones of three sandy beaches. The experiment adopts three beaches: a 1:10 uniform-sand beach, a 1:10 non-uniform-sand beach, and a 1:35 non-uniform-sand beach. This paper reports its measurements on swash water depth, morphology, bedload, and migration of sand particles. It also analyzes the hydraulic jump and sandbar, sorting and sedimentology characteristics, and fractal dimension of bedform. The analysis indicates that the uniformness of sand particle sizes plays an important role in hydrodynamic behaviors, bedform evolution, bedload transport, and migration of sand particles. The fractal dimension of beach profiles lies between 1.15 and 1.25 after swash action, despite changes in bed profiles.

Pre-wetting of sand for high speed oil-water separation

The search for a simple, affordable, and rapid separation method for oil-water mixtures is one of the most serious challenges that the world is facing today. Superhydrophobic, or superoleophilic, materials and surfaces are promising choices for these types of separations. In the present study, a high speed gravity-driven oil–water separation method has been realized by using pre-wetting of river sand, sea sand, and desert sand. The superoleophobicity properties of these pre-wetted sand materials have been found to be good, with a maximum oil contact angle of about 141.1° for desert sand and a minimum oil contact angel of 113.8° for sea sand. Also, the relationship between the porosity of the respective sand type and the water phase separation rate was, for the first time, obtained by using the LBM Shan-Chen model and micro-CT characterization. As a result of a simple particle size screening, the highest kerosene-water separation rate for sea sand was 24.3 ± 2.4 mm/s. In fact, this is the highest oil-water separation rate that has ever been achieved for a sand material. In addition to the effect of sand particle size, other factors affecting the rate of oil-water separation (such as number of separation cycles, thickness of sand layer, temperature, pH value, salt concentration, and different oil-water mixtures) have also been investigated.

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.