Effects Of Erosion Research Articles

Runoff generation and erosion processes at the rock–soil interface of outcrops with a concave surface in a rocky desertification area

Rock surface flow, originating from outcrop surfaces during rainfall, represents a distinctive form of runoff influencing surface erosion and subsurface soil leakage in karst rocky desertification areas. Despite their significance, the processes governing runoff generation and erosion at the rock–soil interface (RSI) under the influence of rock surface flow remain poorly understood. This study aims to elucidate the generation and transformation of runoff at the RSI, along with their scouring erosion effects influenced by rock surface flow from concave-shaped outcrops. Artificial rainfall experiments were conducted on simulated rock–soil structural units featuring exposed rock surfaces and unexposed RSIs of outcrops with concave shapes. Two driving factors, namely rainfall intensity (R) and the inclination of the rock surface (IRS), were manipulated to investigate the formation and output processes of runoffs and sediments from the surface, RSI, and non-RSI (a site away from the RSI). The presence of an exposed rock surface altered the distribution pattern of rainfall–infiltration–runoff. An increase in the IRS led to a significant decrease in surface runoff (p < 0.05). When the IRS was close to vertical, the rainfall-runoff was primarily in the form of surface runoff; however, for inclinations less than 90°, the primary contributors to rainfall-runoff were the RSI and non-RSI runoffs. Surface soil erosion emerged as the predominant form of soil loss, with runoff yield demonstrating a linear positive correlation with sediment production. Both the IRS and R were identified as significant factors affecting surface runoff and soil erosion. Notably, when the IRS was less than 45°, the total soil loss reached its minimum. Therefore, runoff generation at the RSI led to a reduction in surface runoff and an increase in subsurface runoff, contributing to soil leakage at the RSI. Nevertheless, surface erosion remained the primary mechanism of soil loss.

Application of SCMs and seawater to cement-bonded calcareous sand: Macro performance, micro mechanism, and strength prediction

Cement-bonded calcareous sand (C-BCS) demonstrates promising potential for marine island construction due to its exceptional mechanical properties. However, challenges such as freshwater scarcity and the erosive effects of seawater hinder the extensive utilization of C-BCS. To address this, this study comprehensively examines the feasibility of incorporating supplementary cementitious materials (SCMs) and seawater in C-BCS, focusing on macroscopic properties, microscopic mechanisms, and strength prediction. Macroscopic tests reveal that blast furnace slag and silica fume effectively enhance the hydration process and mechanical properties of C-BCS. Moreover, the cemented specimens developed in this study partially meet the strength standards for road pavement sub-base and airport runway upper-base applications. Microscopic analyses indicate that calcareous sand serves as a plentiful source of calcium, facilitating the formation of calcium aluminate silicate hydrate (C-A-S-H) and tobermorite when combined with Al2O3 and reactive SiO2 from slag and silica fume. This enhances the mechanical properties of the samples and their resistance against seawater erosion. Additionally, a back propagation (BP) neural network model accurately predicts the unconfined compressive strength of the cemented specimens. The findings of this study support the broader implementation of SCMs and seawater in practical island engineering projects involving C-BCS.

Event-based soil erosion and sediment yield modelling for calculating long-term reservoir sedimentation in the Alps

ABSTRACT Among the most characteristic offsite effects of soil erosion, reservoir sedimentation is one of the longlasting problems pertaining to storage capacity and dam operations. In this work, sedimentation rates of the Fortezza reservoir in South Tyrol (Italian Alps) are analysed for nine erosive events over 14 months. Sediment rates are calculated through a modified Universal Soil Loss Equation (USLE) combined with a Sediment Delivery Ratio (SDR) module at 2.5 m resolution. The topographic factor is adjusted to the Alpine terrain, and an additional factor is included to consider the nonerodible parts of the basin. The results are validated against a 14-month sediment yield obtained by high-resolution (0.2 m) reservoir bathymetric analyses. The calculated sediment yield has an absolute deviation of 4.8% from the measured one. The results indicate that these methods can be successfully applied for the estimation of reservoir sedimentation rates in the Alps.

Sukanya Samriddhi Yojana: A Closer Look

Savings are paramount in personal finance and economic stability serving as a cornerstone for financial security, goal achievement, and long-term prosperity. By cultivating a habit of saving, individuals can establish a safety net to navigate through emergencies, pursue aspirations such as home ownership or entrepreneurship, and secure a comfortable retirement. Moreover, savings enable individuals to reduce debt burdens, capitalize on investment opportunities, and counteract the erosive effects of inflation, thereby fostering financial independence and resilience. Additionally, accumulating savings empowers individuals to leave a legacy of generational wealth, ensuring the financial well-being of future generations. In essence, savings not only provide a buffer against unforeseen circumstances but also pave the way for realizing dreams, seizing opportunities, and building a brighter future. To promote the savings among the people, the government through banks and post offices offers various savings schemes including fixed deposits, recurring deposits, savings accounts, and government-backed schemes like Public Provident Fund (PPF), National Savings Certificate (NSC), and Kisan Vikas Patra (KVP). The Sukanya Samriddhi Yojana (SSY) stands out among various savings schemes due to its focus on securing the financial future of the girl child in India. The scheme allows parents or guardians to open an account for their girl child below the age of 10, offering a competitive interest rate and tax benefits. Contributions to the account can be made until the child reaches the age of 15, with partial withdrawals allowed for specific purposes such as education and marriage expenses. By keeping all these in mind, this research paper is an attempt to discuss about the features, benefits, eligibility and trend and growth of SSY in terms of Account opening and amount deposited. The trend and growth of SSY has been analysed for a period of 9 years from 2014-15 to 2022-23 by using Compound growth rate technique. The result revealed that there is a positive trend in SSY in terms of number of accounts opened and amount invested.

Haematological and Metabolic Profile Test of Subclinical Mastitis Affected Cross Bred Cattle

The current research was conducted during May–October, 2023 aimed to assess the haemato-biochemical parameters in cattle affected with S. aureus affected subclinical mastitis. Mastitis in dairy cattle is the persistent, inflammatory reaction of the udder tissue. Financial losses due to mastitis occur in the case of both sub-clinically and clinically affected animals. Sub-clinical mastitis exhibits no clinical signs and mostly remains unnoticed by the farmer and can be detected if specific tests are performed in milk samples. Sub-clinical mastitis has an erosive effect on the economy of dairy farmers as it effect directly on the milk quality and quantity. In India prevalence of sub-clinical mastitis was found to be more in cows when compared to clinical mastitis. Blood samples were collected from the jugular vein of 10 healthy and 10 subclinical mastitis affected cattle. Blood samples were analyzed for Hb, PCV, TEC, TLC, while serum samples were examined for ALT, AST, ALP, Glucose, Total protein, Albumin, Cholesterol and Calcium. Haematology report showed significantly (p&lt;0.01) decrease in Hb, PCV and TEC in subclinical affected cattle when compared to healthy animals. TLC was significantly increased in (p&lt;0.01) subclinical affected animal than healthy animal. Biochemical estimate revealed significantly (p&lt;0.05) higher average values of AST, ALP and Ca in subclinical mastitis affected animals compared to healthy animals. Glucose, total protein, albumin, cholesterol and ALT levels are significantly (p&lt;0.05) decrease in subclinical mastitis affected animals when compared to healthy cows. Haemato-biochemical parameters can be used as important for pathological state of subclinical mastitis animals.

Molybdenum erosion in iodine plasma at hollow cathode conditions

In this study, the authors investigate the erosive effects of iodine plasma on molybdenum. By exposing molybdenum samples to three different test cases of iodine vapor, iodine plasma, and argon plasma, the plasma enhancement of erosion was characterized. A roughly exponential behavior with respect to temperature was found in iodine plasma at hollow cathode conditions and erosion rates as high as 70.1 ± 7.7 μm/h. Despite an oxygen content of &amp;lt;1%, evidence of oxidation was found in all test cases. Behavior consistent with preferential oxidation based on grain orientation was found in the iodine test cases.

Investigating the effects of water and wind erosion on different hillslope aspects on the Loess Plateau of China by using 137Cs

Compound erosion is always more intense than singular wind or water erosion in arid and semiarid areas. However, the contribution of different exogenic agencies to compound erosion is difficult to determine. A quantitative study of the proportion of wind and water erosion in compound erosion is necessary to gain insight into and predict compound erosion. In this study, eight slopes with different aspects on a hill were selected in Jingbian County on the Chinese Loess Plateau, which is located in the crisscrossing water-wind erosion region. Compound wind-water erosion was estimated by using 137Cs tracing technology. The contributions of wind and water erosion to compound erosion were distinguished by using two methods, including the revised universal soil loss equation (RUSLE) model and the compound erosion slope divergence characteristics (SDC) method, respectively. The results showed that the northwest windward slope had the highest total erosion rate (76.43 t ha−1 a-1) on all eight slopes with different aspects. The contribution of wind and water erosion to compound erosion partitioned by using the RUSLE model was consistent with that partitioned by using the SDC. The water erosion rate was greater than the wind erosion rate on all slopes. The wind erosion rate was the greatest on the upper part of the northwest slope, which was 27.94 t ha−1 a-1 or 31.38 t ha−1 a-1, as estimated by using SDC method and the RUSLE model and accounted for 36.56 % and 41.06 % of the average annual erosion rate, respectively. The percentage of water erosion was 63.44 % and 58.94 %, respectively. The mutual validation of these two methods provided reliable relative amplitudes of wind and water erosion for compound erosion studies and provided a basis for the quantitative understanding and prediction of compound erosion.

Multi-Fracture Propagation Considering Perforation Erosion with Respect to Multi-Stage Fracturing in Shale Reservoirs

Shale gas is considered a crucial global energy source. Hydraulic fracturing with multiple fractures in horizontal wells has been a crucial method for stimulating shale gas. During multi-stage fracturing, the fracture propagation is non-uniform, and fractures cannot be induced in some clusters due to the influence of stress shadow. To improve the multi-fracture propagation performance, technologies such as limited-entry fracturing are employed. However, perforation erosion limits the effect of the application of these technologies. In this paper, a two-dimensional numerical model that considers perforation erosion is established based on the finite element method. Then, the multi-fracture propagation, taking into account the impact of perforation erosion, is studied under different parameters. The results suggest that perforation erosion leads to a reduction in the perforation friction and exacerbates the uneven propagation of the fractures. The effects of erosion on multi-fracture propagation are heightened with a small perforation diameter and perforation number. However, reducing the perforation number and perforation diameter remains an effective method for promoting uniform fracture propagation. As the cluster spacing is increased, the effects of erosion on multi-fracture propagation are aggravated because of the weakened stress shadow effect. Furthermore, for a given volume of fracturing fluid, although a higher injection rate is associated with a shorter injection time, the effects of erosion on the multi-fracture propagation are more severe at a high injection rate.

Research on Erosion Effect of Various Submerged Cavitating Jet Nozzles and Design of Self-Rotating Cleaning Device

Submerged cavitating jets can effectively remove marine organisms from ship hulls without damaging the surface paint. To enhance the cleaning efficiency of cavitating jets, the selection of an appropriate nozzle structure and the design of an efficient cleaning device are crucial. In this study, the submerged cavitation effect of different nozzles was analyzed by numerical simulation. The actual cleaning efficacy of the nozzles was confirmed through erosion experiments as well. The simulation and experiment showed that the shear nozzle, absent of a pre-shrinking section and featuring a spherical outlet connected to a diffusion cylindrical section, maintained stable erosion performance at a standoff distance of 30–50 mm. This erosion was primarily attributed to denudation caused by bubble collapse. Based on this shear nozzle, a self-rotating cleaning device was designed and manufactured. A test rig was also established to test the cleaning effect and some parameters of the cleaning device.

Impact of forest landscape restoration in combating soil erosion in the Lake Abaya catchment, Southern Ethiopia

As an effect of forest degradation, soil erosion is among Ethiopia’s most pressing environmental challenges and a major threat to food security where it could potentially compromise the ecosystem functions and services. As the effects of soil erosion intensify, the landscape’s capacity to support ecosystem functions and services is compromised. Exploring the ecological implications of soil erosion is crucial. This study investigated the soil loss and land degradation in the Lake Abaya catchment to explore forest landscape restoration (FLR) implementation as a possible countermeasure to the effects. The study used a geographic information system (GIS)-based approach of the Revised Universal Soil Loss Equation (RUSLE) to determine the potential annual soil loss and develop an erosion risk map. Results show that 13% of the catchment, which accounts for approximately 110,000 ha, is under high erosion risk of exceeding the average annual tolerable soil loss of 10 t/ha/year. Allocation of land on steep slopes to crop production is the major reason for the calculated high erosion risk in the catchment. A scenario-based analysis was implemented following the slope-based land-use allocation proposal indicated in the Rural Land Use Proclamation 456/2005 of Ethiopia. The scenario analysis resulted in a reversal erosion effect whereby an estimated 3000 t/ha/year of soil loss in the catchment. Thus, FLR activities hold great potential for minimizing soil loss and contributing to supporting functioning and providing ecosystem services. Tree-based agroforestry systems are among the key FLR measures championed in highly degraded landscapes in Ethiopia. This study helps policymakers and FLR implementors identify erosion risk areas for future FLR activities. Thereby, it contributes to achieving the country’s restoration commitment.

Effect of sulfate erosion on shear characteristics of slurry-reinforced coal body structural faces

To study the effect of sulfate ion erosion on grouted reinforced coal bodies, downhole grouting reinforcement was simulated by artificially prefabricating regular serrated structural surfaces and grouting them with cement. In addition, sulfate erosion tests were carried out at three erosion ion concentrations (3%, 5%, and 10%) and four erosion times (7d, 14d, 28d, and 40d) at a pressure of 0.2 MPa using self-developed constant pressure accelerated erosion equipment, and then, mechanical property tests were conducted using an MTS816 rock mechanics shear tester, which is the most effective way to test the mechanical properties of coal. The test results are as follows: (1) the shear stress–displacement curves of the specimens were of slip type at lower normal stresses and of peak shear type at higher normal stresses, (2) the shear strength of the specimen was linearly negatively correlated with the erosion time and erosion ion concentration, (3) the effect of erosion time was greater than the effect of erosion concentration on the specimen shear strength parameters, (4) sulfate erosion can only affect the degree of shear shrinkage and shear rise and cannot change the damage behavior, and (5) with an increase in erosion ion concentration and the prolongation of the erosion time, the damage morphology of the specimen was shown as the “coal body destruction–nipping fracture–climbing nipping fracture” (coal–pulp interfacial separation) damage form.

Study on the Degradation Effect of Carbonaceous Shale under the Coupling Effect of Chemical Erosion and High Temperature.

The southwest region of China has abundant groundwater and high-temperature geothermal energy. Carbonaceous shale, as one of the typical surrounding rocks in this region, often suffers from deterioration effects due to the coupled action of groundwater chemical erosion and high temperature, which affects the long-term stability of tunnel engineering. In order to investigate the deterioration effects of carbonaceous shale under the coupled action of chemical erosion and high temperature, carbonaceous shale from a tunnel of Lixiang Railway in Yunnan Province was taken as the research object. The microstructure and mineral composition of the samples before and after chemical erosion were obtained with a scanning electron microscope-energy dispersive spectrometer and an X-ray diffraction test. Then, triaxial compression tests were conducted on the samples under different time points and different temperature effects of chemical erosion, and the stress-strain curves and the deterioration laws under a single factor were obtained. An improved numerical simulation method based on the parallel bond model was developed, which can account for the coupled effects of chemical erosion and high temperature on the rock. By simulating the triaxial compression test of carbonaceous shale, the deterioration law of carbonaceous shale under the coupled action was discussed. The results show that chemical erosion has a significant deterioration effect on the triaxial compressive strength of carbonaceous shale, and the degree of deterioration is related to the erosion time. In the first 30 days of erosion, the triaxial compressive strength of carbonaceous shale decreased by 11.38%, which was the largest deterioration range. With the increase in erosion time, the deterioration rate gradually decreased; temperature had a significant threshold effect on the strength of carbonaceous shale, and a clear turning point appeared at about 200 °C. By simulating the deterioration effects of carbonaceous shale under the coupled action of chemical erosion and high temperature, it was found that the longer the duration of chemical erosion, the stronger the temperature sensitivity of carbonaceous shale, and the more serious the loss of compressive strength during the heating process. When the temperature was low, the strength of carbonaceous shale changed little, and some samples even showed an increase in strength; when the temperature was high, the strength of carbonaceous shale decreased significantly, showing deterioration characteristics. The numerical simulation method was compared and verified with the indoor test results, and it was found that the numerical calculation had a good agreement with the test results.

Numerical Modelling of NACA 0015 Airfoil Under the Erosion Condition

Airfoil that experiences erosion caused by flying debris that hit the airfoil can affect the performance of the airfoil. This research was studied to determine the effect of erosion with varying erosion length using numerical methods on the performance of the NACA 0015 airfoil. This research was simulated using the Computational Fluid Dynamics (CFD) approach. Reynolds Averaged Navier-Stokes (RANS) is implemented as the governing equation. The turbulence model used in this research is the k-epsilon model. The Reynolds number used is 1.5 x 10⁶. This research proves that the erosion effect can reduce the Cl value and increase the Cd value on the NACA 0015 airfoil. Increasing the erosion length on the airfoil can also affect the Cl value and Cd value, but this effect is insignificant. In the contour visualization, it can be seen that the airfoil that is experiencing erosion has a pressure contour that increases in the upper chamber and decreases in the lower chamber compared to the airfoil that does not experience erosion so that it can reduce the lifting force of the NACA 0015 airfoil. The flow velocity and streamline contours also show greater circulation in the erosion airfoil, which can accelerate the stall by 1o AoA. Then, variations in increasing erosion length on the airfoil do not show any significant differences in pressure contours or circulating flow.

Detection of Coastal Erosion and Progradation in the Colombian ‘Atrato River’ Delta by Using Sentinel-1 Synthetic Aperture Radar Data

This paper presents a methodology to detect the coastal erosion and progradation effects in the ‘Atrato River’ delta, located in the Gulf of Urabá in Colombia, using SAR (Synthetic Aperture Radar) images. Erosion is the physical–mechanical loss of the soil that affects its functions and ecosystem services while producing a reduction in its productive capacity. Progradation is the deposition of layers in the basinward direction while moving coastward. Other studies have investigated these two phenomena using optical images, encountering difficulties due to the persistent presence of clouds in this region. In order to avoid the cloud effects, in this study, we used 16 Sentinel 1 SAR images with two different polarizations between 2016 and 2023. First, each image was rescaled from 0 to 255, then the image was despeckled by a deep learning (DL) model. Afterwards, a single RGB image was composed with the filtered polarizations. Next, a classifier with 99% accuracy based on Otsu’s method was used to determine whether each pixel was water or not. Then, the classified image was registered to a reference one using Oriented FAST and Rotated BRIEF (ORB) descriptor. Finally, a multitemporal analysis was performed by comparing every image to the previous one to identify the studied phenomena, calculating areas. Also, all images were integrated to obtain a heatmap that showed the overall changes across eight years (2016–2023) in a single image. The multitemporal analysis performed found that the newly created mouth is the most active area for these processes, coinciding with other studies. In addition, a comparison of these findings with the Oceanic Niño Index (ONI) showed a relative delayed coupling to the erosion process and a coupling of progradation with dry and wet seasons.

Atomic oxygen resistance and tribological performance of a self-stratifying Polydimethylsiloxane-polyamide-imide/molybdenum disulfide lubricating coating

Bonded lubricating coatings for spacecraft are subject to the combined effect of the low-earth orbit environment, ground environment and mechanical wear, making it difficult to meet long-life and high-reliability requirements. In this study, Polydimethylsiloxane (PDMS)-modified polyamide-imide (PAI) /molybdenum disulfide (MoS2) coatings were prepared using a self-stratifying strategy. The structural and tribological performance changes of coatings after atomic oxygen (AO) irradiation were investigated. The results showed that the PDMS segments improved the AO erosion resistance due to the inorganic layer produced on the surface of coating. The structural integrity of the binder and lubricant decreased the effect of AO erosion on the tribological performance of lubricating coatings. The PDMS-PAI/MoS2 coating have application prospects in the field of lubricating coating for spacecraft.

A watershed-scale multi-approach assessment of design flood discharge estimates used in hydrologic risk analyses for forest road stream crossings and culverts

Flood peak magnitudes and frequency estimates are key components of any effective nationwide flood risk management and flood damage abatement program. In this study, we evaluated normalized peak design discharges (Qp) for 1,387 hydrologic unit code 16 to 20 (HUC16-20) watersheds in the White Mountain National Forest (WMNF), New Hampshire and in five Experimental Forest (EF) regions across the United States managed by USDA Forest Service (USDA-FS). Nonstationary regional frequency analysis (RFA) and single site frequency analysis (FA) with long-term high-resolution observed streamflow data along with the deterministic Rational Method (RM) and semi-empirical United States Geological Survey regional regression equation (USGS-RRE) were used. Additionally, a hydrologic vulnerability assessment was performed for 194 road culverts as a result of extreme precipitation-induced flooding on gauged and ungauged watersheds in the Hubbard Brook EF (HBR) within the WMNF. The RM outperformed the USGS-RRE in predicting Qp in the gauged and ungauged HUC16-20 watersheds of WMNF and in three other small, high-relief forest headwater watersheds—Coweeta Hydrologic Lab EF’s watershed-14, and watershed-27 in North Carolina and HJ Andrews EF’s watershed 8 in Oregon. However, the USGS-RRE performed better for larger watersheds, such as the Fraser EF’s St. Louis watershed in Colorado and the Santee EF’s watershed 80 in South Carolina. About 31 %, 26 %, and 56 % of the culverts at the HBR site could not accommodate the 100-yr Qp estimated by RFA, RM and USGS-RRE, respectively. Based on the chosen RIs and techniques, it is determined that except for one culvert with diameter = 0.91 m (36 in.), none of the culverts with diameter of 0.75 m (30 in.) or larger are hydrologically vulnerable. Our results suggest that the observation based RFA works best where multiple gauges are available to extrapolate information for ungauged watersheds, otherwise, RM is best-suited for smaller headwater watersheds and USGS-RRE for larger watersheds. Results from the hydrologic vulnerability analysis revealed that replacing undersized culverts with new culverts of diameter ≥ 0.75-m will improve flood resiliency, provided that the structure is geomorphologically safe (with minimal effects of debris flow, erosion, and sedimentation) and allows for both bank-full discharge and necessary fish passage within that design limit. This study has implications in managing road culverts and crossings at Forest Service and other forested lands for their resiliency to extreme precipitation and flooding hazards induced by climate change.

Simulating event-based pesticide transport with runoff and erosion; OpenLISEM-pesticide v.1

This study presents a novel pesticide transport module for the OpenLISEM runoff and erosion model. During water erosion events, high amounts of pesticides can be transported alongside the runoff. Simulating this process helps to mitigate adverse effects of pesticides in the environment. We conceptualized pesticide uptake during runoff with a mixing-layer, including mass transfer of dissolved pesticides into the runoff water and detachment in combination with enrichment of sorbed pesticides. Lateral transport of pesticides is modelled with a kinematic wave based on the overland flow of water. The model simulations were in line with observations for two events in a small agricultural catchment in South-Limburg, the Netherlands. A sensitivity analysis showed that pesticide transport was mainly influenced by the mass transfer rate, the soil-water partitioning and the exponent for the enrichment ratio. The accurate simulation of runoff and erosion by OpenLISEM, enables OpenLISEM-pesticide to simulate transport and redistribution adequately.

The effects of internal erosion on granular soils used in transport embankments

The flooding of embankments used for rail and other infrastructure has the potential to cause lasting weakening of slopes via the movement of fine particles induced by seepage. In laboratory experiments, internal erosion was induced in granular soil samples, with properties consistent with those used to construct transportation embankments, to assess how particle migration through, and out of, samples caused shear wave velocity, strength, stiffness and permeability changes. Shear wave velocity changes, measured using horizontal bender elements, of up to 19 % were observed following fine particle removal of up to 1 % of initial sample mass. Shear wave velocity change was found to be an indicator for identifying the development of permeability change during seepage-induced particle migration. Median measured permeability changes were +5 % and −34 % for samples containing 15 % and 30 % fines, respectively. The largest directly observed permeability and shear wave velocity changes occurred during the initial stages of seepage. Negative correlation was observed between mass of material removed from samples and peak friction angle. Following seepage, soils displayed a dual stiffness behaviour. Stiffness and strength changes were attributed to redistribution of fine particles and opening of pore spaces. Our results have implications for the monitoring of earthworks affected by flooding and seepage as the associated redistribution of fine particles may lead to large changes in slope properties.

Experimental Study on Shear Characteristics of Coal Samples in Different Water-Bearing States

During the establishment of the coal mine goaf reservoir, the strength of the coal pillar dam was weakened by various water–rock interactions triggered by water movement. To explore the influence of the water-bearing state on the shear characteristics of coal pillar dams, the 2–2 coal seam of Shangwan Coal Mine in the Shendong Mining area was taken as the research object and was prepared to coal samples with different moisture contents and different drying-saturation cycles, and the variable angle shear test of coal samples was carried out. The law of water absorption of coal samples under natural and pressurized conditions is obtained. The research results show that the shear characteristics of coal samples change significantly under the action of water, with the increase of moisture content and drying-saturation cycles, the lower the shear strength of coal samples is, the larger the peak shear strain is, and the cohesion and internal friction angle of coal samples decrease linearly. According to the relationship between cohesion, internal friction angle, moisture content, and drying-saturation cycle times, the Mohr–Coulomb model of coal samples considering moisture content and immersion times is established, which contributes to the load-bearing capacity estimation of water-bearing coal mass. Additionally, scanning electron microscope analysis revealed significant changes in the microstructure of coal samples under different moisture states: as the moisture content and dry-saturation cycles increase, the microstructure of the coal samples gradually transforms from orderly and compact to disordered and murky, elucidating the mechanism by which moisture weakens the mechanical properties of the coal samples. The research results provide a useful reference for engineering problems related to the stability evaluation of coal bodies involving the repeated erosion effect of water.

Further study of the erosion mechanism of calcium salt on 517 phase

As the main hydration product of magnesium oxysulfate (MOS) cement, 517 phase (5Mg(OH)2·MgSO4·7H2O) is one of the main sources of MOS cement strength. This paper mainly explores the erosion process and mechanism of calcium ions in the 517 phase. The 517 phase with 94.56% purity was synthesised and the erosion effect of different calcium salts on the 517 phase was characterised. Results show that, in the solution, Ca2+ combined with SO42− in the 517 phase, resulting in an increase in the spacing between the MgO6 octahedron layers in the 517 phase, thus destroying the structure of the 517 phase. Moreover, when ions diffused, the MgO6 octahedron and Cl− recombined into the 518 phase (5Mg(OH)2·MgCl2·8H2O). In addition, insoluble weddellite was found to erode the 517 phase to a certain extent, whereas the 517 phase blended with gypsum was stable. The simulation results of molecular dynamics also showed that Ca2+ had better adsorption ability for SO42− and Cl− than Mg2+. When it was in contact with the 517 phase, Ca2+ was absorbed near SO42− and Cl− was brought into the system.