Decrease In Erosion Rate Research Articles

One hundred years of inlet processes and barrier adjustments at North Inlet, SC

Debidue Beach and North Inlet are a coupled mixed-energy inlet-barrier system along the South Atlantic Bight in South Carolina, USA. Long-term chronic erosion along much of Debidue throughout the 20th century is the result of a shoreline adjustment triggered by an avulsion in the main channel of North Inlet occurring between 1926 and 1934. We use a historical database of shoreline positions compiled by the United States Geological Survey (USGS) and the Analysis of Moving Boundaries Using R (AMBUR) package to quantify changes in the Debidue Beach shoreline over nearly 150 years from 1872 to 2011. This analysis documents relatively large-scale shoreline changes (and equivalent volumetric changes above local depth of closure “DOC”) following the shift in channel position, and a logarithmic decrease in erosion rates over the following decades. Mixed-energy ebb-dominant inlets have considerable effects on adjacent beaches due to their ability to retain and shed large quantities of sand relatively quickly. This study demonstrates that even systems exhibiting long-term stability — like North Inlet — are indeed migrational landforms and should be considered as such when formulating shoreline management plans along adjacent beaches.

Nozzle Wear in Abrasive Water Jet Based on Numerical Simulation.

Particle diameters and jet pressure in abrasive water jet (AWJ) are significant jet properties which deserve a better understanding for improving AWJ machining performance. Some influence factors have been verified regarding nozzle wear in abrasive water jet polishing application. A three-dimensional model of a nozzle is established to analyze the influence of internal multi-phase flow field distribution, which is based on Euler-Lagrange methodology. With the increase of jet pressure, the erosion rate decreases; with the increase of the diameter and mass flow rate of the erosion particles, the erosion speed increases as well. When the diameter of the outlet is worn to 1.6 mm, the pressure on the work piece caused by the abrasive water jet increases by more than double compared to the non-worn nozzle; when the diameter of the nozzle outlet is worn to 1.6 mm, the shear force is 2.5 times higher than the shear force when the diameter is 1.0, which means that the jet force is divergent when the diameter is 1.6 mm, and the damage of the work piece is very serious. The obtained results could improve polishing efficiency on the work piece, extend nozzle lifetimes, and guide the future design of AWJ nozzles.

Records of deep-sea turbidity current activity in the Bengal Fan since the Last Glacial Maximum

The long-term evolution of deep-sea turbidity current activity is closely related to climate and sea level changes; however, the impact of abrupt climate change (e.g. millennial-scale events in high northern latitudes) is poorly known. In this paper, deep-sea turbidite records in the western part of the lower Bengal Fan were identified since the Last Glacial Maximum (LGM) to investigate the effects of abrupt climate change on the development of the Earth's largest deep-sea fan. Our records show a termination of turbidite activity in the western lower fan at 16.6 ka–15.4 ka almost contemporaneous with Heinrich 1 event (a cooling stadial in high northern latitudes). The trigger of this termination in turbidite activity may have been a sharp decrease in erosion rates during a time of relatively stable sea level and rapid source-sink processes. The subsequent episodes of the Bolling/Allerod warm interstadial and Younger Dryas cold stadial and the rapid sea level rise event that followed possibly induced adjustment of turbidity current activities in the Bengal Fan, as indicated by other published records. In summary, we show that close links exist between abrupt climate changes in the high-latitude Northern Hemisphere and deep-sea turbidity current activity in the low-latitude South Asia.

The degradation mechanisms of a nanobainitic steel under cavitation erosion conditions

The nanobainitic steel was investigated using a chamber with the cavitating jet at two distances from a nozzle. Fe-0.6C-1.7Mn-1.6Si-1.35Cr-0.4Mo steel subjected to austenitising at 950 °C followed by controlled air cooling and the isothermal heat treatment at 215 °C shows high strength and good plasticity. The microstructure of steel consists of packets of laths of carbide-free bainite and 10 % in volume of retained austenite in the form of laths, plates, and grains (blocky). Due to its very good combination of strength and plasticity, nanobainitic steel is promising for applications under extreme loading conditions. For this reason, it was decided to analyse the behaviour of the steel under dynamic loads with high-pressure amplitude. Such conditions are obtained during cavitation erosion tests. The distance from the nozzle affected the degradation process (type of damage, maximum and final erosion rates). Three types of damage were observed: A) caused by simple collapse of the cavitation bubble, B) caused by splitting of the cavitation bubble into two smaller bubbles, and C) caused by fragmentation of the cavitation bubble into many tiny bubbles. Some similarities in the appearance of the damage were observed: dark rings with a changed structure and a recess in the middle, a dark surface layer, a quasi-etched structure with numerous small recesses, and a structure with fine needles. The “needle” structure was formed only after reaching the maximum rate of erosion. As the distance from the nozzle increased, more and more cavitation bubbles fragmented, which resulted in an increase in erosion intensity and the maximum rate of erosion. Higher erosion intensity affected the higher transformation of austenite to martensite and finally rounding/convexity of the entire surface and a decrease in erosion rate.

Soil organic carbon induces a decrease in erodibility of black soil with loess parent materials in northeast China

Abstract Although black soil in northeast China undergoes severe erosion, the contribution of parent materials, mainly Quaternary loess and non-loess sediments, to soil erodibility remains unclear. Considering the inheritance of ferromagnetic materials by parent materials, changes in magnetic parameters can successfully determine soil erodibility on a regional scale with a close climatic background. Here, we analysed the magnetic indicators of 142 samples from the black soil horizon formed on loess and non-loess sediments, covering areas of severe and slight erosion in the region to determine the effects of parent materials on the erodibility of black soil in northeast China. Both low-frequency magnetic susceptibility and frequency magnetic susceptibility (χfd) were proportional to the decrease in erosion rate due to erosion-induced leaching of ferromagnetic materials, and the change in χfd was narrow for black soil with loess parent materials, corresponding to relatively low soil erodibility. Compared with loess, the addition of soil organic matter could stabilise soils against erosion, thereby inducing a decrease in the erodibility of black soil formed on loess. Additionally, sustainable soil management policies to protect black soil from further erosion are necessary and urgent under the pressure of maintaining high grain yields and preventing erosion in northeast China.

Experimental study of montmorillonite erosion in low ionic strength water under stagnant and flow conditions in artificial fractures

Compacted bentonite has been proposed as a buffer material in several geological repository concepts for high-level radioactive waste. However, in dilute groundwater, bentonite, especially when dominated by Na-montmorillonite, has been found to be susceptible to erosion and excessive mass loss may compromise the safety of the repository. Herein, results from twelve erosion tests with either flowing or stagnant aqueous solutions, performed with custom-designed artificial fractures made of Poly(methyl methacrylate) are reported. The fracture aperture was 0.1 mm in all tests. Na-montmorillonite or an equal mix by weight of Na- and Ca-montmorillonite were employed. Eleven of the tests were performed with the fracture being vertical, and in one test the fracture was horizontal. The transparent artificial fracture setup allowed monitoring of the expansion of the montmorillonite into the fracture. In all but one test, the diameter reached a limit value, normally within one month of the start of the test. The final diameters varied between 5.9 and 8.7 cm and no clear correlation to flow rate, type of montmorillonite or ionic strength could be discerned. The initial diameter of the emplaced clay was 3.5 cm. The erosion was monitored regularly by turbidity measurements. In general, erosion rates decreased with time and were ultimately low enough that an extrapolation or upscaling of the results to repository scale and operating time would imply a total erosion below the critical value for repository safety. This was the case for all vertical fractures, regardless of montmorillonite type and ionic strength of the aqueous solution. The observed decrease in erosion rates was not due to depletion of montmorillonite at the source because at the end of each test 90% or more of the montmorillonite remained. Further, the ionic strengths were below the critical coagulation concentration, hence gelation cannot provide an explanation to the reduction in erosion rates. Finally, the diameters of the extruded montmorillonite reached the limit while the erosion rates continued to decrease. Consequently, the observed limited expansion was not due to a steady state between erosion and swelling. Rather, the expansion behaviour suggests the presence of frictional forces between the montmorillonite and the fracture walls. The results from this study are beyond the current understanding of montmorillonite colloid behaviour and cannot be explained by existing models.

Effect of climate change on soil erosion indicates a dominance of rainfall over LULC changes

Study regionMahanadi River Basin in India Study focusThis study explores the effect of climate change and human-induced farming and construction activities on soil erosion in a rainfed basin during two time periods viz. 1981–2000 and 2001–2019. This study assesses erosion using the Geographic Information System integrated Revised Universal Soil Loss Equation (GIS-integrated RUSLE) model. Three different analyses are designed to assess the effect i) combined effect of change in all the RUSLE factors over these two time periods, ii) effect of only land use/cover change (LULC), and iii) only rainfall change impact on erosion rate. A modified sediment delivery ratio (SDR) has been proposed and the model performances are validated using the observed Sediment Yield data. New hydrological insights for the regionThe results indicate an overall decrease in the erosion rate as a combined effect of change in all the factors, but at the same time, an increase in the spatial extent of the areas affected by soil erosion is noticed. The mean soil erosion rate varies between 37.02 tons ha⁻¹ yr⁻¹ in 1981–2000 and 31.89 tons ha⁻¹yr⁻¹ in 2001–2019, with a 40% decrease in the maximum erosion rate, while the total and mean erosion rates are both down 13.85% compared to 1981–2000. The analysis suggested overall effect of the change in rainfall is more profound on erosion than LULC change.

Numerical Simulation Study of Hydraulic Fracturing Nozzle Erosion in Deep Well

Hydraulic jet fracturing technology is one of the main means to develop low permeability and deep reservoirs. However, due to the large displacement and high sand ratio in the construction process, the erosion wear of high-speed sand particles on the hydraulic jet fracturing nozzle is more serious, which reduces the erosion cutting ability of the nozzle. Therefore, based on Finnie principle, a three-dimensional model of nozzle is established to analyze the influence of internal multiphase flow field distribution, flow rate, sand diameter and etc. on nozzle erosion. The results show that the erosion velocity increases nonlinearly with the increase of inlet pressure. With the increase of erosion time, the erosion rate gradually tends to be stable; with the increase of fluid viscosity, the erosion rate decreases; with the increase of the diameter and mass flow rate of the erosion particles, the erosion speed also increases, indicating that the size and mass flow rate of the erosion particles are the main factors affecting the erosion effect of the nozzle. The research results have important guiding significance for the rational use of the tool and the extension of the service life of the tool.

Holocene and historic rates of rock coast erosion – A discussion focussed on Southeast England

Cliff erosion is of concern along inhabited coastlines especially under a scenario of increasing sea level rise. Extrapolation of past erosion rates are often used as a first approximation of future rates, which are or form part of the input into numerical models. However, cliff erosion rates in the Holocene are poorly understood. This is due to the generally short record based on historical maps, which can mask or accentuate erosion rates based on different event frequencies, and, for the more recent cosmogenic exposure dating method, it reflects the large number of variables influencing the concentration of cosmogenic nuclides in rocks at the surface of intertidal shore platforms. The study uses historic maps that go back 400 years, updated (to 2020) recent erosion rates, evidence from mid-Holocene terrestrial habitats in front of present-day cliffs, and a geomorphological landscape type interpretation to provide a better understanding of cliff evolution and erosion history for the cliffs in East Sussex (Southeast England). The paper demonstrates that cliff erosion can only have started in the last few centuries with remnants of Eemian cliffs still present in places. This is supported by published 10Be data. The coastline investigated also shows a persistent decrease in erosion rates to less than half the maximum rate observed in the late 19th to early 20th century despite sea level rise. As a consequence, it appears imperative to understand the local drivers of coastal cliff erosion to assess the future consequences of climate change rather than applying general concepts for example in relation to erosion changes with increasing sea level rise.

Rates and causes of black soil erosion in Northeast China

Northeast China is one of the three largest black soil regions on Earth; however, although the black soil of the region is undergoing severe erosion, the dominant erosional agent (wind or water) remains unclear. We studied 12 black soil profiles and used 137Cs analysis to estimate erosion rates. The results, combined with previously published data, show a gradual decrease in erosion rate from west (>3 mm/a) to east (0–3 mm/a) across the black soil region. Correlation of the erosion rates and climatic parameters suggests that wind erosion dominates in the west and water erosion dominates in the east. Using the mean erosion rate (2.22 mm/a) as a reference, the black soil will be completely eroded in ∼113 years. Given the agricultural importance of the black soil region, we suggest that tillage should be reduced throughout the region, and that to control ongoing erosion, revegetation should be conducted by planting herbs in the west and afforestation in the east.

Analysis of Heterogeneous Nucleation and Erosion Behavior Considering the Injection of Impurities into Wet Steam Flow Using Poly-dispersed Method

Nowadays, an enormous amount of electricity is gained from steam turbines, and solid salt injection into the steam turbines is used to control pH. Therefore, the heterogeneous nucleation will occur because of the presence of impurity (solid salt) in the steam turbine's low-pressure stage; and some changes take place in the operation of the turbine stage and power of the steam turbine due to the presence of impurities. As a result, there will be two groups of liquid droplets: the first group includes liquid droplets arising from spontaneous homogeneous condensation, and the next group includes liquid droplets arising from heterogeneous condensation. In this study, the poly-dispersed method has been used in the Eulerian-Eulerian approach for modeling the liquid droplets of each group. In more researches, the effects of heterogeneous nucleation on the supersonic stream among blades of steam turbines of the steam cycle have been neglected. The purpose of this study is to calculate and consider the effects of heterogeneous nucleation by injecting NaCl into the parameters of wet-steam flow, erosion rate, and turbine power. The numerical results gained due to the presence of solid particles (compared to their absence) show a reduction in condensation shock, a decrease in erosion rate, and a 0.022 MW increase in the power of the steam turbine. Overall, the erosion rate of blades and power generation can be considered two important parameters in designing and repairing steam turbine blades.

Reducing the mechanical wear of elbows and pipes due to solid particles flow by using nano coating technique

This work investigated reasons and factors that cause the failure due to mechanical wear (Erosion) for the inside surface of elbows and pipes used in cement transportation which manufactures from low carbon steel and finds out a method for reducing this failure. The technique of Nano-coating layers is used to coat the surface of samples with layers of nanoparticles of tungsten carbides of different thicknesses of (30, 40, and 50 μm). The test was done for these samples by placing them inside the elbow under the same operating conditions, pin on disc test. The results of the test under the same operation condition showed a decrease in erosion rate by 71% for the sample coated with 50 μm of layer, while the results of the pin on disc test showed a decrease in erosion rate by 97% for the thickness of 50 μm as this test is done under ideal testing conditions. The decrease in wear rate for elbow and pipes will increase their life work two times at least and that reduces the cost of maintenance by about 75%. The numerical simulation was also implemented to simulate the erosion profile inside the elbow, and the agreement with experimental results was 90%.

Erosion Rate of Lateral Slope Deposit Under the Effects of Different Influencing Factors

Lateral slope deposits along a channel represent an important source of material for initiation and development of debris flows/floods that are typically observed in many headwater tributaries. This study found that the failure process of such a deposit reflects combined interaction between external hydrodynamic factors (inflow discharge and channel slope) and internal factors (compactness and fine particle content). The erosion process comprises two stages: runoff erosion toward the toe of the deposit body and soil failure owing to gravity. Spatially, the erosion rate is distributed unevenly across the deposit; the highest value occurs at the section close to the middle of the deposit, on the upstream face. Temporally, the erosion rate decreases exponentially. Overall, the average erosion rate decreases (increases) with bulk density (inflow discharge and channel slope). However, a slope of 7 is a threshold at which the tendency of the erosion rate in relation to the fine particle content differs. In comparison with the other three influencing factors, the effect of the fine particle content is much smaller. Although the bulk density of the deposit imposes the most significant effect, it is of the same order as that of both inflow discharge and channel slope. As the failure process can be summarized as repeated runoff scouring of the toe of the deposit, deposit failure, and entrainment of the failure body by runoff, we proposed a calculation method for the total time required for a complete lateral erosion process, and validation of the calculation suggested its reasonability. The findings of this study enhance the understanding of the mechanism of lateral soil deposit failure, which could help improve runoff-induced debris flood forecasting in headwater regions of mountainous catchments.

Flume Experiments on the Erosive Energy of Bed Load Impacts on Rough and Planar Beds

AbstractUnderstanding bed load impact dynamics on exposed bedrock in rivers is crucial to quantifying the erosive energy of a stream. Observations of the bed load saltation trajectories and impact energies are lacking, particularly in channels with nonplanar bed topography. In this study, we performed four flume experiments of saltating gravel to offer new insights on the dependence of particle impact dynamics on transport stage and bed topography. Our experiments used two different boundary shear stresses (τb = 36.5 and 25.4 Pa) and two different bed configurations, planar and nonplanar (bedrock disks uniformly oriented at 10° from the bed surface). For each experiment, we indirectly estimated the impact energies from the trajectories of particles with high‐speed video imaging and measured the erosion rates of rock samples embedded in the flume floor. The planar and nonplanar beds had negative and constant relationships, respectively, between energy delivered to the bed and transport stage. The nonplanar bed had a heavier tailed distribution of impact energy than the planar bed, which implies a greater number of rare highly erosive impacts. Probabilistic formulations of particle trajectories better predict the increase or decrease in erosion rate across experiments than deterministic regression equations. Our findings suggest that bedrock erosion models should consider a distribution of possible bed load impact energies, particularly for natural river channels that have rough surfaces.

Erosion Mechanism and Sensitivity Parameter Analysis of an innovative shaped Curved Pipeline

In the process of natural gas transportation, it is unavoidable for particles to collide with the wall, which will cause erosion of curved pipeline. Reasonable curved pipeline structure can effectively avoid the erosion failure. In this paper, an innovative shaped curved pipeline formed by extrusion of cylindrical indenter is presented. The erosion mechanism and sensitivity parameter analysis of the innovative shaped curved pipeline is studied by numerical simulation and compared with that of ordinary elbow. In addition, the effects of extrusion parameters and particle parameters on erosion of innovative shaped curved pipeline were also studied. The results show that the dent can effectively reduce the maximum erosion rate of elbow. With the increase of dent depth, the maximum erosion rate of elbow is decreasing. With the increase of indenter diameter, the ability to reduce the maximum erosion rate decreases. Under the harsh conditions of large particle diameter and high particle velocity, the dent has a better ability to reduce the maximum erosion wear rate, and the maximum erosion rate can be reduced by 26.8%.

DEM simulation of internal erosion around a submerged defective pipe

Internal erosion caused by broken sewer pipes often leads to ground subsidence in urban area, which is a major risk to public safety and has caused substantial socioeconomic loss. In order to ensure the ground stabilization and the safety of buried pipelines, it is necessary to understand the process of internal erosion around a submerged defective pipe. In this paper, the Dynamic Fluid Mesh (DFM) is coupled with the three-dimensional discrete element method (DEM) to simulate internal erosion in gap-graded soils above a defective pipe. In this fluid-solid coupling scheme, the fluid mesh can be generated according to the soil skeleton formed by coarse particles and updated at regular intervals. Seepage forces are calculated and applied on solid particles in the DEM model. The approach accounts for permeability and porosity changes due to soil skeleton deformation and internal erosion. In this study, some gap-graded soils samples with different size ratio are established. A defective pipe is placed below the sample. After that, different hydraulic gradients are applied to the sample. Fine particles are washed away from the hole in the pipe. The results indicate that the erosion process can be divided into three stages according to changes in the erosion rate. In the initial stage, numerous fine particles are washed away, and the flow rate increases with the increase of eroded particles. Subsequently, the erosion rate decreases and the flow rate tends to reach a steady state. Finally, only a small proportion of particles fall down from the outlets and the erosion rate levels off to zero gradually. Parametric studies show that the increase of hydraulic gradient increase the eroded particle mass. The number of erosion particles from the bottom layer is much larger than those from the upper layers as more fine particles in the upper layers are locked.

Soil erosion: An important indicator for the assessment of land degradation neutrality in Russia

This review of soil erosion (SE) studies in Russia focuses on two main tasks: (i) ensuring the completeness and reliability of SE data in Russia, a large country (17.1 million km2) with a variety of natural and socio-economic causes of land degradation, (ii) assessing the possibility of including a SE indicator among the indicators of land degradation neutrality (LDN). A wide range of statistical, remote sensing, mathematical modeling data, the results of scientific and field studies obtained at different levels were analyzed. It is asserted that in Russia the total area of eroded lands and those under erosion risk occupy more than 50% of all agricultural lands, whereas soil fertility of croplands decreased in Soviet time (from 1950s to 1980s) by 30–60% only due to water erosion. However, recent scientific studies indicate a decrease in erosion rate and in the area of eroded land during the last 30–40 years as a result of abandonment of arable land and subsequent overgrown with natural vegetation. The climate change resulting in decrease of the depth of soil freezing, flow of spring runoff also adds to the decrease of soil erosion. The SE indicator was suggested as an important complement to three global LDN indicators. At national and subnational level, it can be interpreted through such indices as “Rate of soil loss” (ton ha-1 yr-1) and “Total soil loss” (1000 tons, in certain area during selected time period). At local level the set of indices can be wider and site-specific, including those obtained through remote sensing data by using the classifier of thematic applications of remote sensing technologies; the example was tested at the local site.

Modeling of fluid-particle interaction by coupling the discrete element method with a dynamic fluid mesh: Implications to suffusion in gap-graded soils

Abstract A new fluid–solid coupled numerical approach by combining the Dynamic Fluid Mesh method with DEM (discrete element method) is applied to simulate suffusion. The fluid mesh is generated according to the soil skeleton formed by coarse particles and updated at regular intervals. Seepage forces are calculated and applied on solid particles in the DEM model. The new approach accounts for permeability and porosity changes due to soil skeleton deformation and suffusion. A model of soil sample under triaxial stress condition is developed to simulate the suffusion process. The results show that the erosion process can be divided into three stages: initial stage when numerous fine particles are washed away and the flow rate increases with more eroded particles, deceleration stage when the erosion rate decreases and the flow rate tends to reach a steady state, and stabilization stage when the erosion rate levels off to zero gradually. Parametric studies show that the increase of hydraulic gradient and coarse particle size ratio both increase the eroded particle mass. However, high confining stress will decrease the eroded particle mass. Hydraulic gradient affects the whole process of suffusion whereas confining stress and particle size ratio mainly affect the second and third stages.

Viscosity impact investigation on erosion of carbon steel in sand-mixed-polivinyl alcohol

Erosion in oil and gas production sector is predominantly caused by fine particles’ migration into the processing facilities. Fine particles are mostly transported to the facilities via carrier fluid. Other than sand, the viscosity of the carrier fluid also contributes to the sand erosion phenomenon. However, the impact of viscosity on sand erosion is not fully discovered by previous researchers. Therefore, this paper investigated the impact of fluid viscosity on erosion of carbon steel surface. In the presented work, an experimental rig was fabricated and tested for the study of impact of fluid viscosity on erosion of the carbon steel by considering the water mixed-polyvinyl alcohol as a carrier fluid. The metal coupons were impacted with sand slurries of different viscosities. Scanning electron microscopy along with energy dispersive spectroscopy and Universal scanning probe microscopy were used to analyse the centred and adjunct areas of the coupons. These analyses revealed that the viscous slurry is least effective in removal of metal surface in comparison with the pitting erosion. The obtained results reflected a decrease in erosion rate as the fluid viscosity upsurges and the type of metal surface erosion changes from uniform erosion to pitting erosion by fluid viscosity increment.

On erosion characteristics of compacted loess during wetting procedure under laboratory conditions

The erosion of engineered slope surfaces has become an urgent problem in loess regions in China, which has a serious impact on the safety and stability of the slope projects. In this paper, to study the effect of the confining pressure, dry density of the slope surface, and water flow velocity during wetting procedure on the erosion characteristics of compacted loess, we developed a laterally confined uniaxial compression-erosion apparatus, which was characterized by the fact that it can change the confining pressure of the being eroded soil sample to analyze the loess erosion rates and particle size distributions of the eroded sediments. The fractal dimensions of the eroded sediments were calculated by fractal theory and their variations were analyzed. Results show that the erosion rate is approximately linearly related to the confining pressure. The higher pressure has a tendency to move towards the free top of soil sample, the erosion rate increases. Compared with the water flow velocity, the higher confining pressure plays a greater role in the erosion rate, the influence of water flow velocity on the erosion rate decreases. With the increase of dry density, the erosion rate decreases, the higher dry density enhances the ability of soil sample to resist water erosion. The confining pressure changes the particle size distribution of the eroded sediments of loess samples, the median diameter D50 increases. However, the fractal dimension decreases with the increase in confining pressure. The confining pressure of slope surface has a negative effect on the loess anti-erosion characteristics. The results in this paper would provide detailed information on the mechanisms of loess erosion, which could contribute toward prevention of surface erosion of high fill slopes in loess regions.