Coarse Sand Research Articles

Mineralogical and Grain Size Analysis of Bai Hassan Formation Terraces in Al-Teeb Area, SE Iraq

Bai Hassan Formation is exposed as remnants of beds from previous formations due to severe erosion that were removed. Results from grain size analysis revealed that most of the studied sediments were coarse-grained sediments ranging from coarse sand to gravel. The study shows that the sediments are poorly sorted. The values of skewed coefficients ranged from fine to strongly skewed, and the negative values indicate the occurrence of hard changes in the environment. Meanwhile, the kurtosis values for the studied sediment indicate that the differences in these values are due to changes in the flow and sediment sorted in a relatively high energy environment. Light minerals like quartz, and feldspars, and rock fragments are identified. Heavy minerals such as chlorite, amphibole, pyroxene, mica, epidote, zircon, garnet, tourmaline, rutile, kyanite, and staurolite can provide information about the geological processes and environments that occurred in a particular area. These minerals can be indicative of specific rock types, metamorphic or igneous formations, that are derived from high Zagros mountains. The collision between the Arabian Plate and the Eurasian Plate resulted in the formation of the Zagros Fold and Thrust Belt, leading to the uplift and deformation of the Zagros Mountains. The Bai Hassan Formation in Iraq originated during the Miocene epoch from fluvial and alluvial fan environments. Sediments carried by rivers and streams from the elevated mountains in Iraq and Iran were deposited, forming conglomerates, sandstones, and mudstones that reflect various depositional settings such as braided river channels and floodplains indicating a rapidly sinking basin with freshwater and lacustrine environments.

Applicability of Soybean Crude Urease-Calcite Precipitation Method in Various Liquefiable Sandy Soils

Liquefaction is a process in which pore-water pressure generated in the soil, usually by earthquake, is equal or almost equal to the total stress in the soil. This process reduces the effective stress to zero or near-zero, leading to reduction in shear strength and stiffness of soil. Hence, when liquefaction occurs, structures above and within the liquified soil, buildings, bridges, tunnels, docks, underground pipelines, and many other structures can get damaged. Soils which are susceptible to liquefaction are granular soil such as sand and silt. One of the methods that can be adopted to prevent liquefaction is soybean crude urease-calcite precipitation. This method uses urease enzyme in soybean crude as a biocatalyst to hydrolyze urea to produce carbonate ions and ammonium ions. In the presence of calcium ions, the carbonate ions react to produce calcium carbonate (calcite) precipitate. This research investigates the applicability of soybean crude urease-calcite precipitation method to improve various liquefiable sandy soil (fine, medium, coarse sand) at different relative density (40-60%). The soil strength after improvement was evaluated by using unconfined compressive strength (UCS) test, while calcite content was measured using acid leaching method. The results of the UCS test and calcite content analysis varies depending on the type of sand and relative density. The UCS value obtained from medium sand is higher than 50 kPa, potentially sufficient to prevent liquefaction. However, treatment on coarse sand failed to develop UCS, whereas treatment on fine sand produces limited UCS (< 10 kPa).

Particle Size Distribution and Composition of Soil Sample Analysis in a Single Pumping Well Using a Scanning Electron Microscope Coupled with an Energy Dispersive X-ray (SEM-EDX) and the Laser Diffraction Method (LDM)

Soil is a heterogeneous material, and its properties are vital from an agricultural perspective and for groundwater management. However, limited studies have been performed on the soil characteristics (soil texture, water-holding capacity, and soil compositions) of a single pumping well, especially in Malaysia. This article focuses on the soil characteristics and elemental analysis of a single borehole with 11 samples collected around Labu Kubong, Perak. The soil properties were analyzed in the context of particle size distribution (PSD) using the laser diffraction method (LDM), as well as soil composition for elemental analysis using a scanning electron microscope coupled with an energy dispersive X-ray (SEM-EDX). The LDM results revealed the average percentage of clay, silt, and sand to be 0%, 6%, and 94%, respectively, indicating most particles comprised sand particles which in percentages demonstrated a sandy texture with less silt content. Additionally, the water holding capacity is low because of major coarse sand particles in alluvial formations. Moreover, SEM-EDX outcomes displayed an average percentage of elemental composition reported as follows: C (40.77%), O (34.33%), Si (10.66%), Al (5.82%), Fe (1.10%), K (1.10%), As (0.05%), Na (0.04%), and Be (5.62%). Consequently, SEM-EDX outcomes showed these elements were derived from silicified quartz, feldspar, and iron-bearing minerals that originated from shale formations, and the presence of carbon indicates peat formation. Therefore, this study provides information on a single pumping well from an irrigation practice, and this study also recommends regional to global scale studies for supporting sustainable groundwater development worldwide.

Roles of Exposure Time and Geochemical Factors in the Characteristics of the Surface Sediments of the Hwangdo Tidal Flat, Taean, Cheonsu Bay, West Coast of Korea

The Hwangdo tidal flat is an intertidal landform located in Cheonsu Bay, Taean-gun, Chungcheongnam-do, on the west coast of Korea. The topographical characteristics of the semi-enclosed bay on the eastern side of the study area include waterways, sandbars, small islands, and tidal flats. In this study, data were acquired from tide gauges installed on the Hwangdo Bridge, and the height of the ellipsoid was measured using a real-time kinematics global positioning system (RTK-GPS). Digital elevation model (DEM) using Matrice 300 drone data were also acquired after processing. The geochemical sediment characteristics in the study area were analyzed, together with tidal-flat exposure-time characteristics based on environmental factors. Sediment data (n = 107) collected from October 25 to 28, 2022 (Korean local time) were used to classify sediment particles according to Folk and Ward (1957). Sedimentary facies ranged from coarse sand (sand:mud ratio = 9:1) to sandy silt (sZ) followed by muddy sand (mS) and slightly gravelly sandy mud ((g)sM). Total organic carbon (TOC) in the surface sediments was also characterized based on a particle-size analysis. The mean change in tidal height measured at Hwangdo Bridge during the sampling period was ~7.53 m (minimum: −3.86 m, maximum: +3.67 m). Based on the Boryeong’s sea level measurement tide data in 2022, the tidal area in the drone images ranged from 6.362 m2 (0.006 km2) at DEM +4.0 to 4,841,078 m2 (4.841 km2) at DEM −4.0 m, indicating an increase in the tidal-flat area according to the tidal level of up to ~800-fold. The daily average exposure time was 9.0 h (minimum: 1.5 h, maximum: 17.9 h). Based on the results of multivariate analysis using exposure times and a geochemical dataset, four groups were identified: upper, middle, and lower intertidal zones and regions with a relatively high organic-matter concentration. A determination of the main characteristics of the Hwangdo tidal flat according to their spatial distribution showed that, among various environmental factors, changes in the sand or clay sediment composition were determined by community factors. The results of this study demonstrate the four statistically processed groups of marine environmental characteristics in the Hwangdo tidal flats. Changes in sedimentary patterns, rather than in the exposure time, accounted for the differences in the sediment compositions of the upper, middle, and lower stations, a response that is expected to continue.

Analisa Pengaruh Kotoran Organik pada Pasir Kasar Sungai Batanghari terhadap Kuat Tekan Beton

The organic content contained in the sand can affect the quality and improvement of the concrete which will slow down the concrete process. Sand originating from the Batanghari watershed is pretty much inspected in the laboratory of the Faculty of Engineering. The design of the concrete shows that the organic content of sand originating from the Batanghari river basin is quite high. There are 2 variations of the concrete test object, unwashed sand and washed sand, The source of sand from the Batanghaari river Sembubuk village, Kec. Jambi Outer City District. Muaro Jambi which refers to the British standard and ASTM C-33. The aim is to get the levels of organic impurities contained in the coarse sand of the Batanghari river and to determine the effect of medium sand on the compressive strength of concrete. The implementation method refers to SNI 7656:2012 regarding the test method for the procedure for selecting mixtures for normal concrete, heavy concrete, and mass concrete. The concrete test object is in the form of a cylinder with a size of 15 cm x 30 cm. the results of the organic dirt test for coarse sand on the Batanghari Jambi river, namely the unwashed sand is number 4 and for washed sand it is number 2 on the organic plate. The results showed that the average compressive strength of concrete at the age of 28 days on unwashed sand with a compressive strength of 26.28 MPa and at the age of 28 on sand washed with a compressive strength of 29.15 MPa.

Effects of Fractal Dimension and Soil Erodibility on Soil Quality in an Erodible Region: A Case Study from Karst Mountainous Areas

Soil aggregate stability and soil erodibility (k) are crucial indicators of soil quality that exhibit high sensitivity to changes in soil function. Therefore, it is of great significance to explore the quantitative relationship between these indicators and soil quality for effective ecosystem monitoring and assessment. In this study, soil samples were collected from eight altitude gradients in a karst mountainous area; we analyzed 11 soil physical, chemical, and biological properties, and assessed soil quality using the minimum data set (MDS) method. The results revealed that soil aggregate stability, bulk density (BD), pH, and fungal community diversity exhibited a unimodal altitudinal pattern, whereas the soil organic carbon (SOC), total nitrogen (TN), and C:N ratio showed an increasing trend. Among the factors considered, SOC, BD, soil pH, mechanical composition, and fungal community diversity were found to explain the most variation in soil aggregate stability and soil erodibility (k). Principal component analysis (PCA) identified soil fungal community diversity, C:N ratio, coarse sand, and macro-aggregate (MA) content as highly weighted indicators for MDS. The integrated soil quality index (SQI) values, ranging from 0.30 to 0.62 across the eight altitude gradients, also exhibited a unimodal altitudinal pattern. The analysis indicated a significant linear relationship between the fractal dimension (D) and soil erodibility of the EPIC model (Kepic) with SQI, suggesting that D and Kepic can serve as alternative indicators for soil quality. These findings further enhance our understanding of the response of soil properties to altitude changes, and provide a novel method for assessing and monitoring soil quality in karst mountainous areas.

Hydrogeophysical Investigation in Parts of the Eastern Dahomey Basin, Southwestern Nigeria: Implications for Sustainable Groundwater Resources Development and Management

Geoelectrical resistivity measurements were conducted in five locations within the eastern portion of the Dahomey basin for the purpose of subsurface evaluation and detecting saturated zones. The locations are Covenant University (L1), Bells University (L2), Oju-Ore-Ilogbo Road (L3), Obasanjo-Ijagba Road (L4), and Iyana Iyesi (L5). The study was carried out to avert the common challenges of drilling low-yield groundwater boreholes in the area. A total of 30 Vertical Electrical Soundings (VES) and five two-dimensional Electrical Resistivity Tomography (ERT) data sets have been acquired along the study areas. The geoelectrical resistivity results were integrated with the borehole logs to generate the spatial distribution of the subsurface lithologies in the area. The delineated subsurface lithologies include the topsoil (lateritic clay), clayey sand, sandy clay, fine silty sand, coarse sand, and shale/clay units. The fine silty sand and coarse sand units were identified as the two main aquifer units within the area. The depths to the upper aquifer unit in the area include 31.7–96.7 m, 38.5–94.0 m, 30.7–57.5 m, 39.1–63.4 m, and 46.9–57.5 m for locations L1, L2, L3, L4, and L5, respectively. At the same time, the depths to the lower aquifer unit in the area include 43.4–112.7 m, 52.2–108.0 m, 44.2–72.5 m, 53.7–78.5 m, and 63.5–72.9 m for locations L1, L2, L3, L4, and L5, respectively. The estimated hydraulic parameters for both aquifers show they are highly productive with mean porosity, mean hydraulic conductivity, and mean transmissivity of 20–22%, 12.4–17.0 × 10−2 m/s, 1.56–2.18 m2/s for the upper aquifer, and 48–50%, 371–478 × 10−2 m/s, 50.00–62.14 m2/s for the lower aquifer. By focusing on these aquifer systems during exploration, sustainable groundwater resources can be secured, providing relief to homeowners within the study area who might otherwise face the frustration of drilling unproductive and low-yield boreholes. However, it is crucial to consider the presence of sub-vertical faults in the study area, as these faults can significantly impact groundwater development and management. These sub-vertical structural faults may lead to changes in the permeability, hydraulic conductivity, and transmissivity of the delineated aquifers, affecting their productivity across the divide and ultimately influencing the overall water availability in the area. Careful consideration of these geological factors is essential for effective aquifer management and sustainable groundwater utilisation.

Time Dependence of Viscosity of Alkali-Activated Fly Ash Based Geopolymer Mortar

FA was used as the raw material, and the net slurry of FA base Geopolymer was set as the control group to study the influence of sand content, gradation, reaction temperature and time on the time dependence of the viscosity of alkali-activated fly ash based geopolymer mortar. The experimental results show that the curing reaction of alkali-activated fly ash based geopolymer mortar was affected by the temperature dependence of fluid viscosity and the activation energy of the chemical reaction, which is relatively complex. This paper will divide the whole polymerization process into three stages to elaborate. The increase of sand cement ratio will increase the viscosity of FA base polymer mortar. If the sand is too coarse or too fine, the viscosity of FA base polymer mortar will increase significantly, and the fine sand has a greater impact on the viscosity of FA base polymer mortar than the coarse sand. Increasing temperature will significantly accelerate the reaction speed and increase the influence of chemical reaction activation energy on the viscosity of the system while the too high temperature will make the viscosity of the system decrease more significantly in the reaction. This study will reveal the intrinsic relationship between the viscosity of geopolymer and the reaction process, the reaction mechanism of the curing process so that the reaction stage can be represented by the viscosity state of the slurry.

Assessment of Different Growing Media on Cut Flower Performance of Two Gladiolus (Gladiolus grandiflorus) Cultivars

One of the most important problems encountered in the cultivation of cut flower gladiolus is soil-borne diseases and pests. This problem substantially reduces flower yield and quality. Soilless culture is very limited for gladiolus and it has not been studied extensively. The characteristics of the growing media used in soilless culture either directly or indirectly affect yield and quality. Therefore, it is quite essential to determine the appropriate growing media in cut flower cultivation. At the same time good flower production usually depends upon various factors including the type of growing media used. The present study was conducted to determine the effects of two different gladiolus varieties (Gladiolus grandiflorus L. cv. “Purple Flora” and “Ibadan”) and six different growing media (peat+pumice: 1:1, v/v; peat+perlite: 1:1, v/v; rice hull+pumice: 1:2, v/v; coarse sand+peat: 2:1, v/v; soil; and cocopeat) on the some quality parameters of gladiolus in in Batı Akdeniz Agricultural Research Institute (BATEM), Antalya, Türkiye. Quality parameters (stem length, flower stem diameter, stem weight, flowering time, number of florest) were significantly (p < 0.01) affected by the different growing media and cultivars. Among the growing media, the earliest flowering time (77.8 days) and the longest stem length (128.0 cm) were determined in peat+perlite, whereas the largest number of florets (15.0 florets spike-1) were recorded in peat+pumice. Regarding the varieties, Purple Flora (84.7 days) flowered earlier than Ibadan (102.7 days), while Ibadan displayed more superior characteristics in terms of the other parameters.

The Study of Mineral Composition and Free Iron Oxides in Sand Fraction for Tigris and Euphrates Rivers/Iraq

A study was carried out on the mineral composition and free Iron oxides of the sediments of the Tigris and Euphrates river. Two soils were selected representing the sediments of the Tigris (Al-Numaniyah) and Euphrates river (Al-Shamiya), and physical and chemical analyzes were conducted on them, the sand is separated by means of a sieve whose openings are (53 microns) in the presence and absence of oxides into sand separations (53-2000) micrometers, to prepare them for metallurgical examinations. The minerals of soil samples were examined by powder method using diffracted X-rays, and the results showed the following:The results of the diffracted X-ray examinations, the special results of the separated sand in the sediments of the Tigris river showed the presence of Quartz minerals (50.8 and 40.3%), Albite (13.3 and 10.3%) and Chlorite (3.3 and 8.3%) and Micas (5.4 and 6.4%) and Kaolinite (2.2 and 1.5%) for coarse and fine sand, respectively, and the percentage of free Iron oxides in coarse sand was (3.1%). and fine sand (2.9%), and the results of X-ray examinations of the sand separated in the sediments of the Euphrates river showed the presence of Quartz minerals (51.0 and 54.9%) and Albite (23.3 and 18.0%) and Chlorite (3.3 and 3.5%), and Mica (5.4 and 3.3%) and Kaolinite (2.2 and 1.1%) and the percentage of free Iron oxides separated by coarse and fine sand was (2.4 and 1.8) respectively.

Machine learning and RSM-CCD analysis of green concrete made from waste water plastic bottle caps: Towards performance and optimization

This study aims to serve as a performance indicator for the workability and strength of concrete when coarse aggregate, sand, cement, and water are partially substituted with waste plastic bottle caps. The significance of these alternative plastic water bottle caps is to reduce plastic trash that is difficult to lapse and to prevent waste that can be transformed to something that may be employed in the advancement of technology in the future. The principle of "Reduce, Reuse, and Recycle" is used, which not only lowers environmental pollution but also reduces costs. In the building industry, concrete is the most often utilized material. In order to preserve natural resources and minimize the number of materials that end up in landfills, green construction is becoming a more significant worldwide issue. Empty cans and bottle tops from drinking water bottle produce a lot of garbage. The difficulty of biodegrading plastic trash and the need for techniques for recycling or reuse make this a problem for the environment. Such problems are being investigated in this study in order to determine whether it could be possible to partially replace coarse aggregate with 0, 6 and 12% in the manufacturing of concrete using discarded bottle caps. To evaluate the compressive strength, split tensile, and flexural strength test characteristics in a laboratory setting; waste bottle caps were used as replacements for coarse aggregate at different percentages. The highest compressive strength was determined to be 28.80 MPa with 12% replacement of used plastic bottle caps with a water cement ratio of 0.55. Advanced statistical methods, including RSM-CCD (Response Surface Method-Central Composite Design) and machine learning models ANN-LM (Artificial Neural Network- Levenberg Marquardt), were applied in this study to predict concrete performances based on mix design variations. It was found that ANN-LM model displayed more accurate prediction relative to RSM-CCD method.

Eco-friendly soil stabilization method using fish bone as cement material

The method of soil improvement by calcium phosphate precipitation is a novel, environmentally friendly, and non-toxic technique. Such technology provides advantages over ureolytic induced calcite precipitation (UICP), the most popular and widely used method in the field of geotechnical engineering. In this paper, an investigation of the consolidation of fine and coarse sand samples by enzyme induced calcium phosphate precipitation (EICPP) was carried out. Tuna bones were used as an alternative source of calcium and phosphorus ions, as one of the most popular fish species in Japan and the main source of food industry waste. Unconfined compressive strength (UCS) of the samples after 21 days of daily injection of the solution showed an increase in strength up to 6,05 MPa in fine and up to 4,3 MPa in coarse sand samples. X-ray powder diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (SEM-EDS) analysis were performed to investigate the nature and type of deposition. Analyses confirmed that deposition is composed of brushite with needle-like crystals in the case of Toyoura sand and flower-like crystals in the case of Mikawa sand. SEM-EDS showed a presence of both, calcium, and phosphorus in the precipitate, indicating the presence of calcium phosphate compounds (CPCs). This study reveals that tuna bones are a rich source of calcium and phosphorus for EICPP, which results in a strengthening of silicate soil up to 3.4–6.05 MPa and is able to reduce ammonia emissions by 85.7 % - 97.5 % compared to UICP.

Moisture and soil type are primary drivers of Helicoverpa zea (Lepidoptera: Noctuidae) pupation.

Studies in the lab have demonstrated that evaluating the effect of soil moisture and other variables is essential for understanding the importance of environmental factors influencing the Heliothinae pupal stage, but simulated field studies are conducted infrequently. We compared the pupation of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) under saturated and unsaturated conditions across 3 distinct soil types (coarse sand, high organic muck, and fine-textured clay) and observed adult emergence, as well as pupal depth and weight. The interaction between soil type and moisture had a significant effect on adult emergence. Fewer adults emerged from dry fine-textured clay soil than from dry coarse sand and high organic muck. However, there was no effect of soil type and no interaction between soil and moisture on pupal depth. Soil moisture was the primary driver of pupal depth, suggesting prepupae use moisture to mediate their position within the pupal chamber. In addition, pupal weight was unrelated to soil type, moisture, or their interaction. Our study demonstrates that soil moisture can be a greater driver of H. zea pupation than soil type, but additional observations are necessary to understand the mechanism by which moisture impacts pupation.

The effects of suspended bivalve culture on benthic community structure and sediment fluxes in Saldanha Bay, South Africa

This study provides a follow-up to prior measurements of the impact of mussel Mytilus galloprovincialis farming on benthic macrofauna and biogeochemistry and includes the first measurements of the effect of oyster Crassostrea gigas farming in Saldanha Bay, South Africa. The Shannon–Wiener index was significantly lower for farm than for control sites, indicating reduced diversity at farm sites. The lowest values of the Warwick statistic were recorded at the established farm site (R-old). Nested PERMANOVA showed no significant difference in community composition between farm and control sites. Suspension feeders (the mudprawn Upogebia capensis, clam Venerupis corrugata, and holothurian Thyone aurea) dominated at control sites and were important contributors to dissimilarity. Deposit feeders and predatory/scavenging gastropods tended to be more abundant at the farm sites. nMDS ordination showed a clear separation of the more exposed Big Bay stations. The proportions of mud and very coarse sand were moderately associated with community structure. Biogeochemical fluxes showed insignificant differences in sediment oxygen demand between the farm and control sites. Ammonium (NH4) regeneration dominated nitrogen (N) fluxes and was greater at the farm (313 µmol N m−2 h−1) than at the control (187 µmol N m−2 h−1) sites, and maximum rates were restricted to the established mussel raft (R-old) during winter. In contrast, fluxes of oxidised N were less at farm sites relative to the controls. There was no significant difference in phosphate (PO4) regeneration at farm and control stations, leading to higher inorganic N to PO4 regeneration ratios at farm sites.

Density-Dependent Pore Water Pressure Evolution in a Simplified Cyclic Shear Test

When specimens of different sands are produced using the same preparation method and sheared under the same conditions (consolidation stress, loading, etc.), while simultaneously keeping the drainage closed, the resulting tendencies of these sands regarding the PWP build-up will be different. This research paper presents a simplified cyclic shear test, which is used to evaluate the accumulation of PWP in sands under defined specimen preparation procedure and testing conditions. In the proposed experiment, a comparison of different sands with this respect is easily achieved. The principle of this experimental method is based on the evolution of the PWP during cyclic shearing of a water-saturated sand sample. Undrained conditions during the experiment allow for the evolution of the PWP, which is quantified by the rate of the PWP build-up. The duration of a single cyclic shear test, including specimen preparation, is approximately 30 min. The evaluation of the rate of the PWP build-up for different densities resulted in an exponential dependence of the PWP build-up on the variation of the relative density. The results confirmed a higher generation of PWP in a fine sand compared to a coarse sand. A comparison with the results of undrained cyclic triaxial tests in the case of eight different sands demonstrated a good agreement between both experimental methods. The basis for the comparison was the density-dependent evolution of PWP in these methods. The presented method delivers a value (index) that quantifies the PWP build-up in sands under the defined testing conditions.

3D DEM Analysis of Particle Breakage Effect on Direct Shear Tests of Coarse Sand.

This paper explores the effect of particle breakage on the mechanical behavior of coarse sand through 3D Discrete Element Method (DEM) simulations of direct shear tests (DST). The objective is to gain insights into the macro- and micro-mechanical behaviors of crushable coarse sand, with a particular focus on the stress-strain relationship, volumetric deformation, and evolution of grain crushing. The simulations involve a comparison between non-crushable and crushable particle models, where the crushable particles are implemented in the shear zone of the DST subjected to different high normal stresses. The findings indicate that the crushable particles experience partial crushing at peak shear stress, with further particle crushing leading to the production of finer particles at the shearing plane during shearing at the critical state. The migration of these finer particles under pressure and gravity generates their accumulation predominantly in the lower section of the simulation box. Importantly, the presence of crushing in the DST induces a decrease in the shear stress and an increase in the volumetric strain leading to contractive behavior instead of dilation, which gradually stabilizes the volumetric deformation at higher normal stresses.

Constitutive modelling of a coarse sand under unfrozen and frozen states

Constitutive modelling of a coarse sand under unfrozen and frozen states

Low-Quality Irrigation Water Treated Using Waste Biofilters

Although in water-deficient regions, agricultural runoff, drainage water or surplus irrigation water is often used, there are constraints related to its quality to be considered (salinity, nutrients and pollutants). Thus, it is necessary to treat surplus irrigation water considering the low-energy supply systems available to farmers. This work focuses on a nature-based water treatment system consisting of two prototypes of anaerobic bioreactors with horizontal or vertical flow. To enhance the circular economy strategy, two different wastes (coarse sand and almond pruning) were used as bioreactor components. The aim of the research was to monitor the quality of the water (pH, electrical conductivity, suspended solids, chemical oxygen demand, alkalinity and bicarbonate, carbonate and nitrogen contents) before and after the treatment. All the parameters studied (except chemical oxygen demand) were reduced by the treatments, but with large variations. Furthermore, there was 100% nitrogen reduction in the horizontal water flow treatment with the filter bed formed by coarse sand and almond pruning. It was observed that the variation in the concentration of some parameters was associated with the type of filter bed (i.e., the C/N ratio of the residue) and with the design for water circulation flow. Although the findings are promising, further research is needed to achieve reductions in all studied parameters.

Influence of Sand Supply and Grain Size on Equilibrium Upper Regime Bedforms

AbstractNotwithstanding the large number of studies on bedforms such as dunes and antidunes, predicting equilibrium bedform type and geometry for a given flow regime, sediment supply and caliber remains an open problem. Here, we present results from laboratory experiments specifically designed to study how upper regime bedform type and geometry vary with sediment supply and caliber. Experiments were performed in a sediment feed flume with flow rates varying between 5 and 30 l/s and sand supply rates varying between 0.6 and 20 kg/min. We used both uniform and non‐uniform sands with geometric mean diameters varying between 0.22 and 0.87 mm. Analysis of our data and data available in the literature reveals that the ratio of total (bedload plus suspension) volume transport rate of sediment to water discharge Qs/Qw plays a prime control on upper regime equilibrium beds. Equilibrium bedforms transition from washed out dunes (lower regime) to downstream migrating antidunes (upper regime) for Qs/Qw between 0.0003 and 0.0007. For values of Qs/Qw greater than 0.0015, the bedform length increases with Qs/Qw. At these high values of Qs/Qw, equilibrium in fine sand is characterized by upstream migrating antidunes, cyclic steps, and significant suspended load. In experiments with coarse sand, equilibrium is characterized by plane bed with bedload transport in sheet flow mode. Standing waves form at the transition between downstream migrating antidunes and upstream migrating bedforms.

AGGREGATE AS A COMPONENT IN THE PROCESS OF CONCRETE MAKING

<p style="text-align: justify;">By modern design of the concrete system, proper selection of cement and aggregates with appropriate additives as well as other concrete production procedures, satisfactory properties of the finished concrete mass can be achieved. When making concrete, aggregate makes up approximately three-quarters of its volume, which has a great influence on the properties of fresh and hardened concrete. Due to its significantly greater stiffness than that of cement stone, large aggregate grains form the basis of concrete through which forces are transmitted. Small aggregate grains together with cement paste make up the mortar. Although the role of coarse grains and sand in fresh and hardened concrete is different, they are observed together in all tests. The choice of aggregate depends on several factors, where we would especially emphasize its availability. Its characteristics such as: plasticity, workability, strength, density, durability, permeability, texture and color largely depend on the type and quality of the aggregate used in the process of making concrete. It is available to everyone because it is actually a composite material whose basic ingredients are aggregate, cement, water and other necessary additives. This paper will deal with the division of aggregates as well as the most frequently investigated properties of aggregates. </p>