Silt Size Research Articles

Monitoring of suspended matter in the Dnipro River within Zaporizhzhia city, the main trends of 2022

The article presents the results of monitoring observations on the temporal distribution of the qualitative and quantitative components of the Dnipro River suspended matter within Zaporizhzhia city. The research on the territory of this powerful industrial center of Ukraine with a developed metallurgical complex was carried out from 2015 up to 2019 and from the end of 2021 to the present time. The main task of the research was determining the distribution of iron and a group of heavy metals of anthropogenic origin in the composition of the river suspension, and identifying the connections of their concentrations and forms with the natural conditions of the region. Sedimentary matter from the water flows of Dnipro River within research area was sampled once per month using sedimentary traps developed by authors. The methods of electron microscopy (with microprobe analysis) and laser diffraction analysis were used to study the suspension granulometric and chemical composition in the Center for Shared Use of Scientific Equipment of the IGS NASU. SEM studies were carried using scanning electron microscope SEM JEOL-6490 LV (Jeol Ltd., Japan) with an energy dispersive spectrometer of the X-ray microanalysis system INCA Energy+ (Oxford Instruments plc., Great Britain). Particle size analysis was determined using the laser particle size analyzer Mastersizer 2000 with a Hydro 2000S wet dispersion module (Malvern Ins. Ltd, UK).The study results of the samples taken in the first year of hostilities in Ukraine revealed a number of features which were not observed in the previous series of studies. Those peculiarities are the following ones: reduction in the intensity of sedimentary matter accumulation; decrease of technogenic components in the suspension content (in particular, the amount of ferrous metals, changes in the ratio of condensed and dispersed iron particles of silt size, as well as the component composition of fragments of alloys of non-ferrous and ferrous metals). The obtained results may indicate the sensitivity of the component composition of the suspension to changes in the external environment in general, as well as the significant impact of the anthropogenic component on the distribution of iron in suspended matter.

Influence of operating parameters on the silt erosion performance of bare and coated SS304 steel

Purpose The purpose of this paper is to investigate the silt erosion performance of Bare, 75%Cr2O3 + 25%Al2O3 and 85%Cr2O3 + 15Al2O3-coated SS304 under various control parameters such as rotation speed, concentration of silt and particle size of silt used for making slurry. This can provide insight for using chromia and alumina-based coatings for hydro-turbines. Design/methodology/approach Taguchi approach was used to identify the effect of three input parameters on the bare and coated alloys. L16 orthogonal array is used for determining the signal-to-noise (S/N) ratio for each process parameter. For each level of parameters taken into consideration about the erosion wear, the arithmetic mean of the S/N ratio is calculated. On the essence of the results of S/N ratios, it is possible to determine the effect of the most dominating parameters of the erosion wear. Findings Results show that the erosion increases with an increase in silt concentration (Wt.%). It has been analyzed that the rotational speed has the most significant effect followed by the particle size and concentration on erosion wear for all uncoated and coated SS-304 samples. Maximum resistance to erosion is provided by 85%Cr2O3 + 15%Al2O3. The least erosion wear for process parameters has occurred at the optimal parametric combination of rotational speed (N) = 415 rev/min, concentration (C) = 15 Wt.% and particle size range as <53 µm for uncoated and coated stainless steel. Originality/value The study clearly shows the silt erosion performance of chromia and alumina coatings of different compositions at different input parameters. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0028/

Early Holocene occurrence of loess in Folldal, east-central southern Norway: Identification, origin and palaeoclimatic significance

Identified for the first time in Norway, windblown yellowish-brown dust in Folldal, east-central southern Norway, fulfils physical and geochemical criteria for sensu stricto loess, including a high carbonate content. Two extant and one relict marl pond located on low-carbonate rocks are investigated. An allochthonous origin for the marl ponds is suggested and explained by the deposition of suspended clastic carbonate as loess by aeolian processes. The scattered geographical distribution of loess and the need for a calcareous source area suggest a W-SW provenance from a relict valley sandur/existing flood plain in upper Grimsdalen. The mean grain size (~22.4 µm) of the aeolian silt is in the finer range of average loess, explained by the up to 25–30 km long transport and approximately 250–300 m airborne uphill move from the suggested source area to the marl ponds. Based on age-depth modelling using 9 AMS radiocarbon dates, loess deposition occurred from ca. 10,390 to 9780 cal. yr BP (610 years). Two prominent periods of loess accumulation occurred from ca. 10,390 to 10,190 (200 years) and ca. 10,020–9950 (70 years) cal. yr BP. Loess deposition results from W-SW wintertime winds in a dry to semi-arid climate. In southern Norway, W-SW winds in winter are associated with a positive mode of the North Atlantic Oscillation (NAO). From source to deposition, the response time to erode, transport and accumulate loess is suggested to be seasonal to 1 year. An immediate increase in organic production followed loess deposition as early initiation of a warmer and wetter Holocene climatic optimum.

Distribution and Characteristic Sediment Material of Watershed Deli River-Sumatera, Indonesia

Rivers are a source of surface water and bring benefits to human life. River water quality changes along with the development of the river environment which is influenced by various activities and human life. Deli River is one of the rivers used by the people of Medan-North Sumatra as a provider of clean water and various other daily activities and is also used as a transportation route for fishermen. This study aims to determine the flooding conditions that often occur in the Deli River, this is caused by the shallowness and narrowness of the river body. In this study, the quantitative method was taking sediment samples at several points along the river starting from upstream, middle, and downstream with research time on 7 July 2023. The results obtained from this study were river sediment material along the Deli River from upstream to downstream generally has a grain size of 65% sand, a grain size of 26% clay, a grain size of silt 6.3%, and a grain size of gravel 3.7%. The upstream sediments are dominated by sand-sized sediments and in the middle (between the upstream and downstream) the sediments are dominated by clay-sand-sized sediments, while the downstream sediments are predominantly sandy loam. The flooding of the Deli River is caused by the reduced capacity of the river, high intensity of rainfall in the upper reaches, and narrowing of the river and high sediment deposits in the middle to lower reaches so flooding often occurs along the Deli River.

Model studies for desilting basin for Teesta-VI H.E. project, Sikkim – a case study

Desilting basins play an important role in run-of-river hydro power projects on Himalayan Rivers. These rivers carry huge amount of sediment with them, due to steep slopes and fragile geology of the region. The suspended sediment enters through the power intake and ultimately the power house. This causes heavy damage to the turbines and other under water parts. Therefore, desilting basins are provided to eliminate suspended sediment from the water conductor system. The design of desilting basin is verified on a physical model for 90% removal of suspended sediment coarser than 0.2 or 0.3 mm and efficacy of flushing tunnel below in transporting the settled sediment. Central Water and Power Research Station, Pune has conducted physical model studies for desilting basin for various hydro power projects in India and neighbouring countries. One such study, Hydraulic model studies for desilting basin for 500 MW Teesta-VI Hydro Electric Project, Sikkim is presented in this paper. Various design parameters such as length of desilting basin, length and bed slope of inlet transition, outlet transition, size of silt flushing tunnel, size and spacing of openings connecting main basin with silt flushing tunnel etc. were tested during the model studies. The results in terms of settling efficiency for 0.3 mm size particles were obtained.

Diatoms microfossils and their microstructural effects on the sensitivity of metastable silty-clayey soils

In 2013, an accident occurred in Port of Santana, located at the mouth of the Amazon River, in the State of Amapa, Brazil, comprising a large volume of soft silty-clay soil flowing very fast, for a great distance, towards the bottom of the river. Field tests performed afterwards identified the occurrence of sensitive soil layers at the site. Subsequent laboratory tests verified the presence of diatom microfossils in layers with highest liquidity indices. Owing to peculiarities of the accident, a large research programme started at PUC-Rio, aiming to investigate the role of these biomineral grains on soil behaviour. Thus, based on physical-chemical-mineralogical tests performed on samples from the site, higher sensitivity natural soils from Port of Santana were reconstituted. Chemical, mineralogical and grain size reconstitution was carried out using manufactured soils containing equal proportions of minerals as in the natural soils, but with a difference in the portion of non-plastic siliceous grains: a reconstituted soil used quartz, in silt size, and the other used diatomaceous earth. This article presents and discuss results of undrained shear strength data obtained through laboratory fall cone and vane tests, as well as microstructure analyses - including scanning electron microscopy, mercury intrusion porosimetry and X-ray microtomography - in high sensitivity natural diatomaceous soils and reconstituted soils, in the liquidity index range of 1.0 ≤ LI ≤ 1.6. It is shown the fundamental role of the diatom microfossils in microstructural metastability, impacting the high sensitivity measured in soil reconstituted with diatoms and in natural diatomaceous soils.

Evaluation of soil texture classification from orthodox interpolation and machine learning techniques

The current investigation examines the effectiveness of various approaches in predicting the soil texture class (clay, silt, and sand contents) of the Rawalpindi district, Punjab province, Pakistan. The employed techniques included artificial neural networks (ANNs), kriging, co-kriging, and inverse distance weighting (IDW). A total of 44 soil specimens from depths of 10–15 cm were gathered, and then the hydrometer method was adopted to measure their texture. The map of soil grain sets was formulated in the ArcGIS environment, utilizing distinct interpolation approaches. The MATLAB software was used to evaluate soil texture. The gradient fraction, latitude and longitude, elevation, and soil texture fragments of points were proposed to an ANN. Several statistical values, such as correlation coefficient (R), geometric mean error ratios (GMER), and root mean square error (RMSE), were utilized to evaluate the precision of the intended techniques. In assessing grain size and spatial dissemination of clay, silt, and sand, the effectiveness and precision of ANN were superior compared to kriging, co-kriging, and inverse distance weighting. Still, less than a 50% correlation was observed using the ANN. In this examination, the IDW had inferior precision compared to the other approaches. The results demonstrated that the practices produced acceptable results and can be used for future research. Soil texture is among the most central variables that can manipulate agriculture plans. The prepared maps exhibiting the soil texture groups are imperative for crop yield and pastoral scheduling.

Study of Geotechnical Properties of Clays in the Laylan Region and their Suitability in the Brick Industry in Northeastern Kirkuk, Northern Iraq

The research dealt with the study and evaluation of geotechnical characteristics, which included tests of the specific gravity, grain-size analysis, and Atterberg Limits, chemical and mineralogical analyses of samples from the Laylan region, northeast of Kirkuk and the possibility of using them as raw materials in the brick industry. The samples have 31.5% clay, 46.25% silt, and 22.25% sand. From this, it turns out that all samples consist mainly of grains the size of clay and silt and small amounts of sand, and thus the deposits of the region are of a nature (Sandy mud ) according to Folk classification. The results of the soil consistency showed that the soil is of a low to medium plasticity type depending on the plasticity scheme within the standard classification of soils and that it can be formed and take suitable plasticity for the brick industry. Chemical analyses revealed that SiO2 and CaO are the clay deposits main components, indicating the high content of quartz and calcium carbonate, The mineralogical analysis by X-ray diffraction techniques indicated that quartz, calcite, feldspar, gypsum, and dolomite are the non clay minerals; Kaolinite, illite, palygorskite and chlorite are the most clay mineral .

Correlation development of erosive wear and silt erosion failure mechanisms for pump as turbine

One of the factors contributing to the gradual decline in the performance as well as the failure of hydropower plants over the years is silt erosion. Several researchers have developed empirical correlations for the prediction of erosive wear of hydro turbines, but these correlations are not directly applicable in practice as the materials examined for the impeller blades were different from the actual impeller material. In this study, an effort has been made to experimentally evaluate the silt erosion of the Pump as Turbine (PAT). The novelty of the study is to use the same material (SS304) for the specimens used for the analysis as well as for the impeller. The experiments were performed with three silt sizes of 100–350 μm, 350–700 μm, and 700–1000 μm; with three different silt concentrations of 0.75 %, 1 %, and 1.25 % for the duration of 18 hrs, 36 hrs, and 54 hrs. An empirical correlation is established for the assessment of normalized wear of the PAT impeller in terms of silt size, concentration, and operating time based on the experimental data. This correlation can be utilized to estimate normalized erosive wear of PAT impeller made up of SS304 material with an inaccuracy of ±15 %. According to the analysis, silt concentration was found to be a more significant parameter in causing erosion than silt size. Additionally, scanning electron microscopy was used to conduct a thorough analysis of the erosive failure mechanism of SS304 specimens. According to the analysis, silt size was observed to be an important factor in producing various types of erosive failures. The material removal from the substrate’s surface was found to be caused by plastic deformation and surface ploughing.

Sedimentological, Mineralogical, and Geochemical characters of the Tigris River floodplain sediment in the Al-Alam area-Tikrit, Northern Iraq

The mineralogical investigation, geochemical analysis, and grain size calculation were carried out for floodplain sediment in the Tigris River to identify the properties of the sediment. The average values of the three main sediment classes, very fine sand, silt, and clay are 9.67, 62.53 and 27.80%, respectively. The silt size fraction was predominant. The classification and nomenclature of surface sediment types from the floodplain of the Tigris River are sandy-silt and mud, and they are the dominant sediment. Statistical parameters of grain size analysis refer to the average of the median values 3.74 Φ very fine sand; mean in average 6.16 Φ coarse silt; standard deviation evident by average 1.30 Φ poorly sorted, skewed; in average -0.14 negatively skewed, and the average of Kurtosis 2.80 very leptokurtic. The samples analysed by the XRD technique revealed clay minerals (chlorite, illite, montmorillonite, and kaolinite) and non-clay minerals (quartz, feldspar, calcite, and dolomite). The heavy minerals identified as species were zircon, tourmaline, rutile, garnet, olivine, hornblende, pyroxene, kyanite, and magnetic particles. The concentration of major oxides by geochemical analysis indicates a high content of SiO2 and CaO in the floodplain of the Tigris river.

Temporal and Seasonal Variations of Silicate Svratka River and Sediment Characterization, Czech Republic: Geochemical and Stable Isotopic Approach

This study investigated weathering and hydrobiogeochemical processes in a silicate dominated watershed (Svratka river) in the Czech Republic in comparison with nearby carbonate dominated catchments. Elemental and isotopic analysis of river waters, particulates and sediments provided a more holistic view of weathering contributions, anthropogenic contamination, biological activity and evasion or sinks of CO2 to the atmosphere. In water samples, we determined total alkalinity after Gran 1974, and cations and anions were determined with inductively coupled plasma–optical emission spectrometer and ion chromatograph. δ13CDIC in water samples was determined with isotope ratio mass spectrometer. pCO2 and saturation indexes of calcite and dolomite were calculated with PHREEQC speciation program. Evasion fluxes were calculated after Broecker, 1974. Isotopic composition of carbon and nitrogen in particulate matter and sediments were determined with isotope ratio mass spectrometer. Mineral composition of sediments was determined with XRD method and elements with XRF method. Further enrichment factors of elements were calculated. The Svratka river, which is the major tributary of the Dyje river, is dominated by Ca2+ > Na+ > Mg2+ > K+ and HCO3− (as total alkalinity). Partial pressure (pCO2) concentrations range from close to 0–572-fold of atmospheric pressure. Isotopic composition of carbon in dissolved inorganic carbon (δ13CDIC) value ranged from − 13.3 to − 8.0‰ reflecting degradation of organic matter and exchange with the atmosphere. Bicarbonate weathering intensity for the Svratka river at its mouth is 11.8 mol/(l⋅km2⋅s), more on par with silicate terrains and lower than nearby carbonate watersheds. Isotopic composition of carbon (δ13C) and isotopic composition of nitrogen (δ15N) values of river sediment reflect soil and temperate plant (C3 plant) values, while higher δ15N values could be attributed to application of organic fertilizers in lower reaches. The river sediments, which came from weathering of crystalline rocks, are dominated by silt size, geochemically less mature quartz, feldspar and muscovite particles. All the stream sediments examined revealed slightly increased amounts of Zn, Cu and Pb. However, using Al as the normalization element to calculate enrichment factors, Zn, Cu and Pb are only elevated downstream, related to industrial contamination. This study is important for local and global level since it deals with contribution of weathering rates and contribution of CO2 to the atmosphere in silicate watershed.

Sediment depositional pattern in the northern Japan Sea over the last 1200 ka and its linkages to orbital forcing

The semi‐enclosed marginal Japan Sea is sensitive to global changes and responds to orbital‐scale variability. Sediment core samples from Integrated Ocean Drilling Program Site U1423 were processed for detrital grain size and semi‐quantitative mineral analysis to assess the sediment characterization and depositional environment in the Japan Sea over the last 1200 ka. The mean grain data suggest the dominance of the silt size fraction over sand and clay in the whole period, while sand content increases dramatically between 600 and 150 ka. The end‐member energy modelling of grain size data suggests that sediment deposition took place under two energy conditions over the last 1200 ka. The low‐energy conditions observed during the middle Pleistocene transition (MPT) is mainly related to the wind deposition with the sediment characteristics being moderately to poorly sorted and coarse to nearly symmetrical skewed during global cooling and enhanced East Asian Winter Monsoon (EAWM) winds in the northern Japan Sea. Post MPT, periodic fluctuations between higher and lower energy conditions are observed, and the depositional environment is controlled by the EAWM wind, and precipitation intensity, glacio‐eustatic sea‐level changes and sea‐ice volumes. During the period, detrital sediments are poorly sorted and nearly symmetrically skewed, marked by the dominance of quartz, plagioclase and k‐feldspar. The spectral analysis grain size‐related data shows the presence of 228, 41 and 23 kyr orbital paced cycles, which are also observed in the Chinese Loess Plateau's normalized quartz mean grain size. This study is the first report of 228 kyr cycles from the Pleistocene Japan Sea sediments indicate that sediment deposition in the Japan Sea is associated with ~200 kyr eccentricity cycle as in the Chinese Loess Plateau.

Carbon stabilization pathways in soil aggregates during long-term forest succession: Implications from δ13C signatures

Forest restoration increases organic carbon (OC) sequestration mainly via the additional litter input and improvements in soil structure that result in biochemical and physical C stabilization over the short term. However, the pathways of long-term C stabilization in soil aggregates during forest succession are unclear. To characterize the long-term C fluxes, the aggregate-associated OC content and C flow pathways were examined over 160 years of secondary successional chronosequence from Lespedeza bicolor to Quercus liaotungensis. The contribution of plant-derived C (litters and fine roots) to aggregate-associated OC was assessed using 13C natural abundance. The proportion of macroaggregates increased but microaggregates decreased along forest succession, and the macroaggregate-associated OC content increased from 4.6 to 28 g kg−1 during succession. The 13C enrichment trend was common in all aggregate size classes: macroaggregates to silt and clay size classes. The maximum δ13C was −23‰ in the silt and clay size classes in the pioneer weed stage at 20−30 cm soil depth. The C pathways followed the trend from macroaggregates to silt and clay size classes. The intensity of the C flows decreased in the topsoil (<10 cm), but plant-derived C stocks within the aggregates increased during forest succession over the 160 years. Notably, fine roots made a greater contribution to the OC accumulation within aggregates than aboveground litter did. The microbial biomass was an important factor affecting fine root-derived C stocks in the aggregates. Concluding, this analysis of natural δ13C signature provides detailed insights into long-term C stabilization pathways associated with soil aggregates during forest succession.

DEPOSITION OF Al2O3/Cr2O3 CERAMICS HVOF SPRAYED COATINGS FOR PROTECTION AGAINST SILT EROSION

Hydro turbines are one of the most vital and essential components for the production of hydroelectric power. Since the hydro turbine is always operating under the influence of water and the silt transported by the water from the hilly region, it poses a lot of threat and damage to the turbine blades working constantly under the action of silt laden water. Erosion wear is the most common type of damage, and drastically affects the life of turbine runners and blades. The introduction of thermal spray coatings, namely high-velocity oxy-fuel (HVOF) technique, has resulted in a major improvement in stainless steel erosion resistance. Ceramic coating powders primarily Al2O3, Cr2O3, and a composite mixture of composition 55% Cr2O[Formula: see text] Al2O3 were deposited on stainless steel substrates of grade 304. The thorough experiments utilizing silt slurry are conducted at different particle size of silt in the range 212–250, 150–212 and 53–106[Formula: see text][Formula: see text]m. The silt concentration has been varied in the range 12–42% by weight, and the substrate was rotated at a rotational speed in the range 600–1500[Formula: see text]rev/min for the test time of 4[Formula: see text]h. SEM images were used to assess the surface morphology of the required testing samples. The erosion observance and the material removal mechanism were investigated and discussed on the basis of microstructure studies. Cr2O3 coating is found to be more resistant to erosion than other coatings under all test conditions.

Studying environment characteristics of cultivation land in Dai Thinh Area, Me Linh District, Ha Noi city to serve sustainable development of health safe vegetables

Cultivation land (Planting Soil) is a natural resource that plays an important role for organisms and humans. Soil pollution will badly affect human and animal health through food, vegetables, fruits, medicinal herbs, etc. To clarify the characteristics of the geochemical environment and estimate the quality of the soil environment in the Dai Thinh area, Me Linh district, Hanoi city, the authors combined the using of traditional and modern methods in the research process, such as: field research methods, grain-size analytical method plus X-ray fluorescence spectroscopy (XRF) method to determine the major components (oxides) of soil. The high-frequency inductive plasma source spectroscopy combined mass spectrometry (ICP-MS) method and optical AAS atomic adsorption spectroscopy have been used to determine the concentration of critical heavy metals in soil samples. Besides, the direct measurement method used to determine environmental indicators (pH, Eh, Ec). Research results show that agricultural soil in the studied area belongs to the group of heavy sandy loam, sandy loam, and sandy clay soils, with average content of sand (size of 0.05-2mm): 60.8 (%), silt (limon) (size of 0.005-0.05mm): 17.96 (%), clay (size of &lt;0.005mm): 21.46 (%). The soil has not been yet polluted by critical heavy metals such as: As, Cd, Cu, Zn, Cr, Ba, Sb, Co, Mo, Se and Sn. The soil in the studied area shows neutral acid-base values (average pH is 6.61), has a strong oxidizing environment (Eh &gt; 150mV) (with values of Eh ranging from 183 to 310 mV), and is not saline (values of Ec ranging from 58.7 - 317.0 (µS/cm). Therefore, in terms of the results of determining environmental physical-chemical criteria and heavy metal concentration, the soil in the studied area can be used for health safe vegetable production. The research results not only serve as a basis for assessing the quality of the soil environment for safe healthy vegetable planting, but also serve as a scientific basis for the authors to propose a number of appropriate solutions to protect and improve the quality of vegetables, land environment protection, contributing to the planning and sustainable use of agricultural lands for the studied area.

Distribution of nitrogen storage in density and size fractions varied with tillage practices and cropping systems with residue return in black soil of Northeast China

AbstractCrop residue return can prevent the degradation of cropland caused by conventional tillage practice in Northeast China. Meanwhile, additional nitrogen (N) input from crop residue inevitably changes soil N pools. Our objectives were to evaluate soil N storage changes in soil physical fractions. The residue return treatments consisted of no‐tillage (NT) and moldboard plow (MP), combined with continuous maize (Zea mays L.) (MM) and maize–soybean [Glycine max (L.) Merr.] rotation (MS) cropping systems, that is, NTMM, NTMS, MPMM, MPMS; conventional tillage (removal of crop residue and deep plow) with continuous maize (CTMM) was included as a control. The concentration of total N (TN) in bulk soil and physical fractions (light fraction [LF], sand, silt, and clay) was measured. In 0‐to‐5‐cm layer, TN content was higher in NT than MP, whereas the result was opposite in 10‐to‐20‐cm layer. Thus, the stratification ratio (SR) of soil TN was greater under NT. The TN content in MM was greater than MS under both tillage practices with residue return. Residue return treatments increased soil N storage by 6.44–24.85% in 0–20 cm compared with CTMM. Continuous maize increased the N storage in all physical fractions, whereas the decrease of silt‐N storage was observed in MS. Overall, it was concluded that residue return could enhance soil N storage, whereas the distribution of N storage changes in LF and sand size fractions was influenced by tillage practice, and the distribution of N storage changes in silt size and clay size fractions was influenced by cropping system.

Geologic processes in marine “muddy” sediments

Marine muds, or “muddy” sediments, represent a broad range of sediments containing a mix of clay and silt size components, often with some smaller amount of sand sized and larger material. Sediments characterized by these broad definitions comprise most of the modern global seafloor, except for areas proximal to terrigenous inputs, such as continental shelves and glacial margins, which can receive and retain a higher proportion of coarser sediment. Beyond the coastal zone, the distribution of marine sediments is driven by a combination of geological, biological, and physical oceanographic processes that themselves are a response to variations in environmental conditions (e.g., global climate, nutrient availability, tectonics, terrestrial erosion). At the local scale, sediment source variation, seafloor bathymetry, primary transport and near-bed currents, resuspension and reworking, and bioturbation contribute to the short- and long-term geologic nature of marine muds. The structure, quantitative compositional descriptions, and physical properties of marine muds from several environments will be compared and the techniques used to analyze them will be presented. New methods that may facilitate an improved understanding of the role and importance of muddy seafloor and shallow sub-seafloor sediments in influencing the acoustic environment will be highlighted.

Soil wind erosion resistance analysis for soft rock and sand compound soil: A case study for the Mu Us Sandy Land, China

Abstract Mixtures of soft rock and sand have been applied extensively in the Mu Us Sandy Land (MUSL, also known as the Mu Us Desert) to limit the loss of top soil by wind erosion. In this study, the efficacy of sand-fixing technology was investigated in a series of experiments. The sand-fixing effect of seven different mixtures (ratios) on soft rock and sand was evaluated in a wind tunnel. The results indicated that the MUSL soils are susceptible to wind erosion, as the textural composition of sand is dominated by coarse particles. MUSL soils dominated by silt and clay particle sizes are more resistant to wind erosion. Each soft rock and sand combination experiences severe wind erosion. However, wind erosion was significantly reduced when soft rock and sand were mixed. An increase in particle size was associated with an increase in the resistance of soft rock and sand mixtures to wind erosion. The ability to resist wind erosion was greatest when the ratio of soft rock and sand was between 1:2 and 1:5. This study provided data to support the approaches to sand-fixing commonly used at present in the MUSL. The results of this study have important practical significance for the improvement of agricultural land potential in dry sandy areas.

A Comprehensive Review on Investigation of Sediment Erosion of Pelton Wheel Turbine

Hydro turbines installed at different hydropower plants face the issue of sediment erosion. Sediment erosion is an ambiguous phenomenon influenced by several parameters, including silt concentration, size, jet velocity, diameter, and fluid viscosity. Silt erosion imposes severe issues for hydropower plants, like shutdown and maintenance costs. The hydro turbine efficiency decreases with the increase in sediment erosion and eventually the breakdown of turbine components. Various researchers conducted small-scale experimental bench studies and numerical simulations to analyze the influence of the above-mentioned parameters on silt erosion, but the actual flow conditions are too complex to simulate. Therefore, no such erosion model has been developed to predict exact erosive wear. This paper presents an extensive review of the literature survey on sediment erosive wear of hydro turbines, both the adopted methodology by previous studies and parameters affecting sediment erosion in Pelton turbine are summarized. Based on literature studies, various aspects of erosive wear, parameters influencing it, and its severe effects on efficiency are thoroughly discussed. Appropriate remedial measurements for erosive wear made by multiple researchers, erosion models developed so far, and their measuring accuracy and the future scope of this research study are articulated in detail.

Hydro-abrasive erosion modelling in Francis turbine at different silt conditions

Hydro-abrasive erosion creates problems for the safe and effective running of hydropower projects. This is of even greater concern in hilly regions. The huge losses in the revenue of the hydropower plant have become a burden on the hydropower project developers. These losses are mainly due to the reduced capacity of the generation of electricity units (kWh). The high amount of silt entering the plant, especially in the monsoon season causes heavy hydro-abrasive erosion in the turbine and other underwater components. The deterioration of underwater plant equipment due to this kind of erosion can also lead to a total shutdown of the hydropower plant. In the current scope of the study, efforts have been made to validate the existing erosion models for the Francis turbine with the operational hydropower plant and carry out the numerical erosion modelling in the Francis turbine to predict the turbine efficiency losses at maximum and part-load conditions. Various developed erosion models are analyzed for the study period of FY 2018–19 based on influencing parameters like silt concentration, silt size, hardness, and site-specific flow constant. The site chosen for this purpose was the MB-II hydropower plant, a 304 MW hydropower project having four generating units of Francis turbine located at the foot of the Himalayan hills in the Uttarkashi district of Uttarakhand, India. The calibration factor is calibrated for the MB-II hydropower plant using GRG Nonlinear algorithm using a multi-start solver.