Stages Of Erosion Research Articles

Investigating the important role of landslide dam geometry on breaching based on numerical experiments

The geometry of a landslide dam is one of the most important factors influencing its breaching process. Understanding how geometric parameters affect breaching is crucial for breach flood assessment and warning strategy development. In this study, numerical simulations were conducted by computational fluid dynamics method to systematically investigate the effect of the landslide dam geometry on the breaching process, with variables including the dam crest length, bottom length, upstream slope angle, downstream slope angle, and channel gradient. The simulation results were calibrated via laboratory tests with a satisfactory agreement. According to the erosion characteristics, the process of landslide dam overtopping failure could be divided into two stages, i.e., headward erosion and overall erosion, and the breach evolution, hydrodynamic characteristics, and erosion processes at the different stages were analyzed. Additionally, the findings indicated that the crest length, downstream slope, and channel gradient all significantly impacted the headward erosion process of landslide dams. At the overall erosion stage, the dam bottom length and maximum lake volume were the key influencing factors. Furthermore, we presented empirical equations to predict the time of headward erosion, time to the peak discharge, and peak discharge at the laboratory scale. Finally, the established empirical peak discharge prediction equations were extended to a dimensionless form, which are applicable to landslide dam failures of various scales. Our study successfully revealed the quantitative relationship between geometric parameters and breaching characteristics, which are beneficial for assessing hazard risk and developing mitigation strategies for landslide dam disasters.

Upslope inflow-driven variations in microtopography and size fractions effect on rill erosion in purple soil hillslopes

Upslope drainage area contributing inflow to downslope rill erosion can be affected by the dynamics of eroded sediment and soil surface microtopography. However, limited information has previously not recognized the variation of the sediment particles and microtopography on hillslopes where upslope inflow perpetually exists. A series of scouring flume experiments were performed on a 15° slope under upslope inflow rates (4, 6 and 8 L min−1) to investigate the inflow-driven microtopography and sediment particle-size distribution (PSD) during the rill erosion process. The results indicated that the surface elevation decay mostly occurred in the later stage of rill erosion. The spatial variability of microtopography increased gradually with increasing inflow rates, and obvious microtopography sharpness intensified with the development of rill erosion. The surface runoff under the 8 L min−1 inflow rate increased by 15.03 % and 90.14 % for 6 and 4 L min−1, respectively, and the sediment yield reached a maximum at the rill stabilization stage (RS). The overall particle-size distribution was mainly composed of silt-sized particles, accounting for approximately 40.97 %−50.15 % of the total eroded sediment. Considerable depletion of clay fractions occurred in the rill erosion process. High inflow rate significantly enhanced variation amplitude of critical hydrodynamic parameters (e.g., flow velocity, flow shear stress and Reynolds number). The spatial heterogeneity of microtopography was correlated with the coarser fraction of sediment PSD in rill erosion, suggesting that erosion processes were affected by the interaction between eroded sediment distribution and roughness. These findings highlight the importance of the PSD of eroded sediment and the development of soil surface structure for an in-depth understanding of the purple soil erosion mechanism at the hillslope scale.

The Relationship between Cholesteatoma Stage and Hearing Bone Erosion Degree in Chronic Suppurative Otitis Media Patients with Cholesteatoma at Dr. M. Djamil General Hospital, Padang, Indonesia

Introduction: Chronic suppurative otitis media (CSOM) is a chronic inflammation of the middle ear mucosa and mastoid space. Cholesteatoma is an ectopic keratinized epithelial tissue that develops through the mucosa of the middle ear cavity and desquamates, resulting in the accumulation of keratin and epithelial debris. This study aimed to determine the relationship between the stage of cholesteatoma and the degree of erosion of the ossicles in patients CSOM with cholesteatoma at Dr. M. Djamil General Hospital, Padang, Indonesia.
 Methods: This study was an observational case series study. A total of 70 research subjects were included in this study, and the research subjects met the inclusion criteria. The inclusion criteria in this study were patients with a diagnosis of CSOM with cholesteatoma at Dr. M. Djamil General Hospital, Padang, Indonesia and have complete medical record data. Data analysis was carried out using SPSS software version 25. Correlation analysis between cholesteatoma stage and degree of osseous erosion was performed using the Spearman correlation test, p<0.05.
 Results: The majority of research subjects were aged 21-30 years (28.6%) and were male (51.4%). Based on clinical symptoms, the majority of patients experience otorrhoea for 5 to 10 years (47.1%), perforated type membrane total tympani (54.3%), degree of erosion of the ossicles type D (48.6%), stage 4 cholesteatoma (61.4%) and granulation tissue (81.4%).
 Conclusion: There is a relationship between the stage of cholesteatoma and the degree of erosion of the ossicles in patients with CSOM (chronic suppurative otitis media) with cholesteatoma at Dr. M. Djamil General Hospital, Padang, Indonesia.

Morphological change and its response to human activities in the estuary of Minjiang River, China, since last early century

AbstractThe evolution of subaqueous deltas in mountain rivers is highly sensitive to variations in sediment load and hydrodynamic conditions, and human activities can rapidly alter these parameters. To better understand the evolution of the subaqueous Minjiang River Delta (MRD) under human activities, we investigated the effects of construction of reservoirs, channel training walls, land reclamation activities, and sand mining from 1910 to 2010. Analysis of bathymetric and fluvial discharge data revealed that the MRD shoals generally experienced slight development during the study period, but with alternating stages of erosion and deposition that were related closely to sediment discharge and the role of human activities. The northern MRD was more strongly affected by decreasing sediment load, while the southern MRD was more influenced by land reclamation. Human activities in the MRD can be divided into five stages: Weak (before 1935), blockage (1935–1950), slight strong (1950–1970), strong (1970–2000), and stable (since 2000). Correspondingly, the geomorphic evolution of the MRD can also be divided into five stages: Natural evolution, channel blockage, southern channel erosion, divergence, and degradation. Furthermore, the morphodynamic response time of MRD to a decrease in riverine sediment was found to be less than 10 years, which is much faster than the morphodynamic changes observed in large‐scale estuaries and deltas. These results provide further insight into interpreting morphodynamic changes in typical small/medium‐sized estuaries and deltas under various human activities.

A Theory of Slope Shear Scouring and the Failure Mechanism of PFC3D on a Gangue Slope

In this paper, scouring shear failure theory is optimized based on the gangue slope near the thermal power field in Baiguo Town, Panzhou City, Guizhou Province. Based on the particle flow PFC (particle flow code) 3D fluid–solid coupling method, the scouring failure mechanism of ditch no. 5 of the gangue slope is comprehensively analyzed from the perspectives of the failure mode, displacement, motion track, and stress–strain. We consider the scouring shear theory in respect of (c, φ); this theory is dominated by two types of scouring intensity factors and can effectively explain the internal mechanisms of gully formation. The rainfall scouring failure of gangue slopes can be divided into four stages: (1) integral splash erosion and local pitting at the bottom of the slope; (2) erosion diversion and pitting in the slope; (3) the tributary–slope crest extension schist erosion stage; and (4) integral gully erosion and the landslide stage. The failure process is not only characterized by discontinuous failure but also occurs in the order of bottom–middle–branch–top. A three-section stepped effect is observed during the process in which the gangue is scoured and destroyed, which fully verifies the intermittent characteristics of the scouring and destruction of gangue slopes. During the whole process, the maximum displacement is concentrated at the top of the slope, and its proportions are as follows: top of the slope > tributary > middle of the slope > foot of the slope. The peak displacement of the slope crest in the horizontal Y-direction accounts for 41.76%, and that in the Z-direction accounts for 45.84%. Scouring deposits can be divided into the arc erosion deposit mode and the sector erosion deposit mode. Mainstream gullies primarily control whether deposits are characterized as arc or straight erosion deposits. The later stage of the second phase of scouring is the incubation period of the tributary gully. The large accumulation makes the stress at the bottom of the slope increase sharply, and the fluctuation value is between 2 and 6.8 MPa. The generation of the branch notch is mainly determined by X-direction stress, and 8.6 MPa is the critical stress. In efforts to prevent and control rainfall and landslide, the slope foot area should be preferentially protected, and the soil mass in the slope should be reduced to prevent the maximum energy fluctuation caused by scouring, so as to prevent significant displacement damage of the slope top.

Numerical investigation of the seepage mechanism and characteristics of soil-structure interface by CFD-DEM coupling method

Interfacial seepage on soil-structure interface is common in water-related engineering, such as dam, culvert, water tunnel, foundation pit, etc. As a weak part in the project, seepage failure on soil-structure interface has caused many project accidents. However, there are few studies on the seepage mechanism analysis of soil-structure interface. In this paper, a series of numerical tests of interfacial seepage are carried out using CFD-DEM coupling method. The seepage mechanism and characteristics of different soil layers in the seepage device are analyzed and a formula for calculating the critical hydraulic gradient of the interface is discussed. The main conclusions are as follows: (1) The seepage flow on soil-structure interface will go through three stages: stability stage, transition stage and particle erosion stage; (2) The porosity and flow velocity of soil on the interface are greater than those in the far-field soil at the beginning of seepage flow; (3) The particle erosion on the soil-structure interface occurs earlier and the erosion degree is more serious than that of the far-field soil; (4) The critical hydraulic gradient of the interface rises nonlinearly with the increase of the degree of soil compaction; (5) The formula for calculating the critical hydraulic gradient of the interface could predict the numerical test results well.

Experimental study on bonding performance of GFRP bars-recycled aggregate concrete under sulfate attack environment

The sufficient bonding performance between glass fiber reinforced polymer (GFRP) bars-concrete is essential for the composite section's integrity. In addition, sulfate attack is one of the primary causes of concrete damage, which will inevitably lead to a decline in bonding performance between GFRP bars and recycled aggregate concrete (RAC). This paper uses the GFRP bar-RAC pull-out test to study the effect of recycled aggregate (RA) replacement rate and RAC protective layer thickness on bonding performance under continuous sulfate immersion. The results indicated that as the sulfate attack time increases, the bond strength of various GFRP bars-RAC specimens rises and then decreases. At the same time, as the RA substitution ratio grows, the specimen requires less time to reach its peak of bond strength, and the bond strength decreases rapidly in the later stages of erosion. When the erosion age reaches 360 days, the bond strength of specimens with recycled RA rates of 0%, 25%, 50%, and 100% drops by 12.93%, 15.18%, 17.99%, and 28.22%, respectively, compared to those without erosion. Since sulfate attacks RAC from the outside, the bond strength of the specimen with a thin protective layer thickness decreases faster after long-term erosion. Through the fitting analysis of the variation law of bond strength of 7 groups (147) specimens, a prediction model of GFRP bars-RAC bond strength is developed, considering the influence of RA substitution ratio and protective layer thickness under continuous sulfate immersion. The ratio of all predicted values to experimental values ranges between 0.94 and 1.133. It provides reliable guidance for the GFRP bar-RAC structure's durability design.

EXPERIMENTAL ESTIMATE OF EROSION MECHANISM AT THE EARLY STAGE OF GULLY FORMATION<a href="#FN1"><sup>1</sup></a>

The article presents results of experiment and its theoretical justification aimed to study the mechanism and intensity of the early stage of gully head formation. The experiment was carried out using the jet installation that allows to change the angle of the water stream from 0.5 to 90° with the flow velocity of up to 6 m/s. The flow angle was changed with a 10° step, while the flow velocity was maintained in the range of 1.01–1.04 m/s. The intensity of soil erosion positively correlates with the flow angles (angles of attack) in the range from zero up to 40°. When the angle was increased to 50–90°, the intensity continuously declined. The lowest absolute values of erosion intensity were observed when the water flow was normal to the soil surface. There are two main reasons why the intensity of soil erosion changes with changing angle of stream flow; the first is hydraulic, the second is hydro-mechanical. The former determines weakening and destruction of inter-aggregate bonds by the water penetrating into the soil; the latter – by the combined vectors of forces of hydrodynamic head and forces keeping the particle (aggregate) in place. The experiment showed that the maximum impact of water jet on a separate soil particle occur at angle of 41°. The flow in a gully happens occasionally and the results obtained should be attributed to the early stage of erosion: the stage before formation of a so called gully headcut.

MIDDLE EOCENE IN THE ALPINE RETROFORELAND BASIN (NORTHERN ITALY): SEDIMENTARY RECORD OF A “MESO-ALPINE” ARC-TRENCH SYSTEM IN THE ALPS

The middle Eocene Cibrone Formation of Brianza (central-western Lombardy) represents an important stratigraphic record to understand a key step of the tectonic evolution of the Alpine range poorly recorded elsewhere. Quantitative petrographic analysis of turbidite arenites, well-constrained in age by the biostratigraphy of interlayered marlstones based on calcareous foraminifera and nannoplankton, allowed us to identify a possible vertical compositional trend within the Cibrone Fm. and to document the NP17 nannofossil Zone (Bartonian) in central Lombardy exposures, east of the Ternate Formation outcrop area. Variable arenite compositions are interpreted to reflect contributions from different source areas, i.e., recycled orogen, island arc, and starved continental shelf. In a paleogeographic scenario still open to different interpretations, the proposed reconstruction supports a classical plate tectonics model for arc-trench systems. The stratigraphic gap, recorded everywhere in Lombardy, between the Eocene succession and the base of the Gonfolite Lombarda Group (upper NP24 nannofossil Zone, early Chattian), corresponds to the earliest stage of continental collision, uplift and erosion that climaxed in the Neo-Alpine Phase.

FEM-SPH adaptive method for analysis protection mechanism of B4C ceramics

To simulate the collision of a tungsten heavy alloy projectile with different velocities on the B4C ceramic target, an adaptive conversion model from Lagrangian elements to SPH particles is developed due to the limitations of the traditional finite element method (FEM) with the element erosion technique. By comparing the simulation results with experimental data and FEM simulation results, the accuracy and effectiveness of the model were validated. According to the damage morphological characteristics, the target damage was classified into the central crush area, cone cracks area, radial/circular area, and fragment falling area by analyzing the damage nephogram, and the formation causes of each area were discussed in detail. According to the simulation results, the impact process between the projectile and target is split into three stages: initial impact stage, erosion stage, and crack propagation stage, and the energy dissipation in each phase was computed and examined. Finally, the protection mechanism is summarized in detail. This study contributes to improve the protection mechanism system of B4C ceramic target.

Characteristics of Soil Organic Carbon (SOC) Loss with Water Erosion in Sloping Farmland of Southwestern China during Maize (Zea mays L.) Growth Stages

Due to frequent human disturbance and the influence of crop growth and development, the migration of soil organic carbon (SOC) in sloping farmland is considerably different to those in other ecosystems. The impacts of maize over its entire growth period on the SOC loss in sloping farmland on purple soils under different erosion stages were investigated, in 2016. This was undertaken using rainfall simulation tests on 15° slopes with a rainfall intensity of 1.5 mm·min−1, in Sichuan Province, China. In this study, erosion development, fluctuating increasing trends in the surface runoff yield, interflow runoff yield, sediment yield, and dissolved organic carbon (DOC) migration flux were observed. Opposite trends were observed in the DOC mass concentration, total soil organic carbon (TOC) content of the sediment, the SOC content of sediment particle state, the DOC content of the sediment, and the SOC enrichment ratio. The DOC migration flux in the surface runoff and in interflow of the rill erosion stage was 1.39–2.84, 3.22–7.78 times significantly higher than that of the sheet erosion stage at each maize growth stage, respectively (p < 0.05). The average DOC mass concentration in the surface runoff, the total DOC content of the sediment, and the SOC enrichment ratio in the sheet erosion stage increased by 100.58–146.44%, 44.44–126.15%, 141.32–191.26%, respectively, compared with the rill erosion stage. Under the experimental conditions, we found that DOC loss mainly occurred at the seedling and mature stages for maize. We also found that maize growth could promote the production of soil interflow, leading to intense soil loss occurring at the subsurface. Compared with DOC mass concentrations in the surface runoff, there was an increase of 4.90–28.29% in the soil interflow, indicating that soil interflow plays a more important role in DOC loss. The growth of maize could impact formation of surface runoff and interflow, reducing the loss of SOC caused by soil erosion. This study helps to understand the carbon loss process in agricultural production in purple soil areas.

Phenomenological Model of Cavitation Erosion of Nitrogen ION Implanted Hiped Stellite 6

Abstract Stellites are a group of Co-Cr-C-W/Mo-containing alloys showing outstanding behavior under cavitation erosion (CE) operational conditions. The process of ion implantation can improve the CE resistance of metal alloys. This work presents the elaborated original phenomenological model of CE of nitrogen ion implanted HIP-consolidated (Hot Isostatically Pressed) cobalt alloy grade Stellite 6. The ultrasonic vibratory test rig was used for CE testing. The nitrogen ion implantation with 120 keV and fluence of 5 × 1016 N+/cm−2 improves HIPed Stellite 6 cavitation erosion resistance two times. Ion-implanted HIPed Stellite 6 has more than ten times higher CE resistance than the reference AISI 304 stainless steel sample. Comparative analysis of AFM, SEM and XRD results done at different test intervals reveals the kinetic of CE process. The model includes the surface roughness development and clarifies the meaning of cobalt-based matrix phase transformations under the nitrogen ion implantation and cavitation loads. Ion implantation modifies the cavitation erosion mechanisms of HIPed Stellite 6. The CE of unimplanted alloy starts on material loss initiated at the carbides/matrix interfaces. Deterioration starts with cobalt matrix plastic deformation, weakening the carbides restraint in the metallic matrix. Then, the cobalt-based matrix and further hard carbides are removed. Finally, a deformed cobalt matrix undergoes cracking, accelerating material removal and formation of pits and craters’ growth. The nitrogen ion implantation facilitates ɛ (hcp—hexagonal close-packed)) → γ (fcc—face-centered cubic) phase transformation, which further is reversed due to cavitation loads, i.e., CE induces the γ → ɛ martensitic phase transformation of the cobalt-based matrix. This phenomenon successfully limits carbide removal by consuming the cavitation loads for martensitic transformation at the initial stages of erosion. The CE incubation stage for ion implanted HIPed Stellite 6 lasts longer than for unimplanted due to the higher initial content of γ phase. Moreover, this phase slows the erosion rate by restraining carbides in cobalt-based matrix, facilitating strain-induced martensitic transformation and preventing the surface from severe material loss.

Case Study: Remote Monitoring of a Solids-Management System in the UKCS

_ A well in the Southern North Sea was shut in due to clay and proppant production. Before it was shut in, it had been producing 1,199 B/D. The challenge presented by the operator was to clean out the well and reestablish production. The operator wanted to boost sustainability metrics and reduce emissions as much as possible. Adding further complexity to the project, the platform in use was a normally unmanned installation (NUI). This type of platform meant no crew could stay overnight and resulted in several new challenges being considered upfront. 1. Remote monitoring abilities were crucial. 2. A reliable, accurate information flow was key for planning workflow during the day. 3. The work window was reduced to 12 hours per day, so maintenance and the emptying of solids had to be carried out during the day. 4. Limited crane capacity was available for the rig-up and assembly. The above considerations, coupled with the ability to remove personnel on board (POB), the efficiency of solids handling, and compact footprint, meant the DualFlow 5K PSI desander was selected as the equipment of choice by the operator. Advance Planning A 7-week wellbore cleanup was planned to reinstate production while also removing the clay/proppant solids. During this time, the FourPhase team also monitored the well performance. Understanding the space constraints offshore was key. To kick off the project, a feasibility report was developed to capture basic well data, which included flow rates, oil/gas properties, pressure, temperature, expected solids production, and expected erosional rates. A site visit was arranged to identify laydown areas, pipework routing, connections, utilities, and rig-up possibilities. Simulations were also carried out to assess the flow and erosional performance and to ensure the planned work was within the operational window of the desander. By creating a 3D rig-up simulation in advance, it was determined that an efficient rig-up could be achieved. This stage also created logistical efficiencies, as accurate measurements for equipment and piping ensured that minimum excess material was shipped offshore. This approach further boosted the ESG metrics of the projects. Implementation The desander contains two patented, single-liner cyclones in one unit. As one vessel is isolated and flushed, production continues through the other, delivering a proven separation efficiency of 99.8% and a dynamic range of 20-μm to 10-mm solids up to 20,000 B/D and 20 MMscf/D. The result is continuous production and better asset management because the data allow early stages of erosion to be managed. Due to its design, it was uniquely able to tackle the specific challenges posed by this project. The system was monitored by the operator’s nearby control platform, where the well could be shut in if there was an emergency. The Operations and Technology Centre in Bergen, along with the FourPhase Aberdeen facilities, remotely monitored the system’s key operating parameters. From a POB perspective, the solution removed traditionally labor-intensive manual operations such as valve manipulation and flushing operations. These operations were run automatically or with a click of a button remotely. Removal of such operations directly reduced POB and associated emissions.

Effect of Initial Surface Scratches on the Cavitation Erosion Behavior of 316L Stainless Steel Substrates and 316L Stainless Steel Coatings

Rough surfaces have been widely considered as negative factors affecting cavitation erosion resistance. However, this study presented the opposite result. Here, 316L stainless steel substrates and the arc-sprayed 316L stainless steel coatings were subjected to a specific grinding process that introduced scratches on the surfaces. The surface hardness values of these ground specimens were measured to evaluate the influence of the grinding-induced strain hardening. The cavitation erosion performance of the specimens was evaluated. The results showed that rough surfaces with scratches could enhance the cavitation erosion resistance, particularly at the early stage of cavitation erosion. The scratches had a greater effect on the cavitation erosion resistance of the coatings than on the substrates. Moreover, rough surfaces with initial surface scratches could extend the incubation period of the 316L stainless steel substrates due to the inhibition of the plastic deformation. The SEM observation showed that the scratch structure of the coating surface inhibited the growth of cracks and the propagation of cavitation pits. This study could also serve as a reference for investigating the cavitation erosion behaviors of materials with a particular surface feature.

The role of straw mulching in shaping rills and stabilizing rill network under simulated extreme rainfall

Straw mulching has been widely demonstrated as a useful practice for soil and water conservation, but its effectiveness in controlling rill erosion has rarely been systematically studied. The objective of the current study was to evaluate the effects of straw mulching on rill development and rill network evolution. A cinnamon soil was mulched with corn straw segments at five different rates of 0, 2.1, 4.2, 6.3 and 8.4 t ha−1, to attain the surface coverages of 0%, 10%, 20%, 30% and 40%, respectively, and received four 30-min simulated rainfalls at the intensity of 90 mm h−1. The structure from motion (SfM) photogrammetry was applied to measure soil surface elevation changes upon each rainfall. Straw mulching was found to retard runoff initiation, but decreased soil losses were typically acquired at the mulched treatments with 20% or more straw coverages. Nevertheless, this conservation effect did not monotonically increase with mulching rate, because a larger number of straw segments were more likely to induce rill erosion via surface flow convergence, thereby increasing total soil loss. Straw mulching also changed the course of rill development. Head retreat dominated rill erosion at the control without mulching throughout the entire experiment, suggesting an early stage of rill erosion. With the straw segments around and at the bottom, the initially equivalent contributions by headcutting, bed scouring and sideward erosion quickly shifted to the predominance of bed incision and then to sidewall expansion, successively. The rapid transition of rill erosion subprocess in this way, together with the dendritic and stabilized networks, indicate a mature stage of rill development by the end of the experiment. The rill depths and main channel widths, as a consequence, were typically smaller at the mulched treatments. These findings demonstrate the effectiveness of adequate straw mulching in stabilizing rill network in addition to reducing soil erosion at the plot scale, and hold important implications for agricultural management in slope farming systems.

Variable response of particles and inorganic carbon of two different soils during splash erosion

Splash erosion caused by raindrops is the first stage of water erosion that detaches and transports soil particles. As an important component of soil particles, soil inorganic carbon (SIC) contains little information on its redistribution during splash erosion. In this study, two soils, purple soil and loess, were selected and placed in a soil tray with a diameter of 20 cm at the center of a splash tray, and a rainfall simulator was used to simulate three raindrop energies in experiments to investigate the migration of soil particles and SIC. The results showed differences in the amount and selective migration of splashed material between the soils, which was evident in the obvious sorting of the particle size of purple soil with distance and the insignificant change of loess soil. The SIC sorting characteristic performed differently in the two soils, that is, the SIC content of purple soil increased with particle size, while that of loess was the opposite. The enrichment and depletion of SIC during splash erosion varied with soil type, and differed from the general enrichment of soil organic carbon (SOC). The SIC enrichment ratio (ERIC) of purple soil was generally > 1, whereas the ERIC values of loess were < 1. In addition, multiple linear regression (MLR) models were established to predict the SIC content of splashed material. Rainfall splash plays an important role in SIC migration and may further affect the carbon cycle. These preliminary results provide a basis for further study of SIC response to rainfall splash.

Experiment investigation on effects of elastic modulus on cavitation erosion of silicone rubber

Research into cavitation phenomena in various fields shows that the elastic modulus of a boundary has a potential impact on cavitation erosion. To obtain the direct relationship between the elastic modulus of the boundary and cavitiation erosion, single-layer samples with different chemical composition and moduli, and double-layer samples with different elastic moduli and the same surface layer material, were prepared with silicone rubber. The results of cavitation experiments on single-layer samples, show that the coating chemical composition and mechanical properties together affect the cavitation morphology of the coating, and dominant factors vary with erosion stage. Through the cavitation test of double-layer samples, it was found that there is a positive correlation between the elastic modulus of the coating and the degree of cavitation. This study helps us to understand the relationship between coating elastic modulus and cavitation more directly, and provides theoretical and technical guidance for the application of anti-cavitation for elastic coating in engineering.

Study on erosion and stability of the ecological slope

Rainfall is the main influencing factor causing slope erosion, landslide, and instability in loess; thus, it is vital to comprehend the process of rainfall erosion on various slope surfaces and water penetration inside the slope. In this paper, the loess sample is from Heifangtai in Gansu Province, and triaxial shear tests were conducted on loess with roots under varying water contents to evaluate the slope-reinforcing impact of roots. The slope surface erosion process was analyzed using a soil moisture sensor and matric suction meter to monitor the variation of matric suction in the middle slope and slope foot in response to varying precipitation levels. The numerical simulation approach is utilized to analyze the fluctuation of slope stability under the effect of varying rainfall intensities and humid heat, and the analytical solution of the safety factor is compared to the model solution. The results indicate that the shortest generation time for bare slope runoff is 6 min, whereas the greatest generation time for the Bermuda grass slope is 12 min; the shorter the period, the less water penetration and the simpler it is to reach the slope erosion stage. The slope’s rise increases runoff velocity, strengthening water resistance on the slope surface. When the test slope is 30°, the maximum mass of scouring sediment on the bare slope is 15.2 g from 24 to 36 min, compared to 14.7 g from 24 to 36 min when the test slope is 60°. The amount of scouring reduces as the slope increases. The slope safety factor declined from 3.51 to 2.84 after 24 h of heavy rain, and the loss rate accelerated as the rainfall intensity increased.

Raindrop-impact-induced ejection characteristics of surface particles for soils with a textural gradient

The ejection of surface soil particles caused by raindrops is an important stage of water erosion. Generally, surface soil is typically comprised of more complex structural units (e.g. crumb, block, or platy structures) rather than single granular structures (e.g. aggregate), especially on surface soil influenced by the different arrangement mode between soil particles. Thus, soil aggregate samples as a selected test material cannot properly characterise the particle ejection characteristics of surface soil with more complex structural units during rainfall. Considering this issue, undisturbed soil samples with a textural gradient were collected as test materials for this study and a needle-type raindrop simulator was used to simulate rainfall experiments. Our results demonstrate that, the first 6 min of rainfall is the key period for particle ejection. During this phase of the experiment, the clay-sized and fine-silt-sized particles were preferentially ejected, and the enrichment ratio (ER) of those particles decreased progressively from sandy loam to silty clay loam. With increased rainfall duration, the soils with a low clay content (e.g. sandy loam, silty loam and loam) were found to develop surface crusts more easily compared with clay loam and silty clay loam. Although the formation of soil crust reduced the size-selectivity of the splash-detached particles, the percentage of sand-sized particles in splash-detachment particles showed an increasing trend, while the percentage of clay-sized and fine-silt-sized particles showed a decreasing trend. The finding of this study suggests that identifying changes in the soil surface condition, as determined by soil texture, is the key factor affecting the ejection characteristics of surface soil particles during splash erosion.

Погребальные комплексы геоархеологического местонахождения Усть-Кеуль 1 (Северное Приангарье): проблемы культурно-хронологической идентификации

This paper presents results of a study of two burial complexes from the geoarchaeological site Ust-Keul 1 in Northern Angara region (excavations of 2012). Mortuary rites and grave goods were analyzed, thus making clear the issue of cultural affiliation of these complexes and defining their uniqueness for the Baikal-Yenisei Siberia. The burials were made by a method of inhumation in ground graves. In both cases structures above and within the graves are absent. The accompanying burial goods are presented by arrowheads with a triangular shape, a concave base and equally large barbs, and by a horn made connector (a cartridge case), the one that was used to attach the stone arrowhead to the arrow shaft. Results of the radiocarbon dating determine the age of the burials by the Late Bronze Age – the Early Iron Age. The dating raises the question about a time of the Tsepan culture bearers` infiltration into the Northern Angara region. Results of the odontological analysis are presented and even based on the description of the extremely fragmented remains, it was possible to define sex and age characteristics of the buried ones. The unearthed fragments and isolated teeth belonged to three individuals. The stage of tooth crowns formation and dental enamel erosion are indicators of the age of the buried ones. Two of them are adolescents (burials 1 and 2, individual 2), and the age of the third individual (burial 2, individual 1), based on the erosion, is between 35–45 years. The results of our research obtained not only with reliance on analogies with other burials in the Northern Angara region but also based on credible radiocarbon data, corroborate the assumption of a somewhat earlier dating of the Tsepan culture burials. There is a discussion about possible infiltration of the Tsepan culture bearers in the Northern Angara region at the end of the Late Bronze Age. However, the issue of a more reliable chronology of these burials under study still remains relevant. The radiocarbon data indicate, at first sight, their earlier age but measurements obtained for burial 2 from the two individuals have large discrepancies. Additionally, they may appear older due to a freshwater reservoir effect. The accompanying burial goods are scarce but allow us, with confidence, to define the burials from Ust-Keul 1 site as belonging to the Tsepan culture.