Study on the Shear Strength and Erosion Resistance of Sand Solidified by Enzyme-Induced Calcium Carbonate Precipitation (EICP).

Sand solidification of earth-rock dams is the key to flood discharge capacity and collapse prevention of earth-rock dams. It is urgent to find an economical, environmentally friendly, and durable sand solidification technology. However, the traditional grouting reinforcement method has some problems, such as high costs, complex operations, and environmental pollution. Enzyme-induced calcium carbonate precipitation (EICP) is an anti-seepage reinforcement technology emerging in recent years with the characteristics of economy, environmental protection, and durability. The erosion resistance and shear strength of earth-rock dams solidified by EICP need further verification. In this paper, EICP-solidified standard sand is taken as the research object, and EICP-cemented standard sand is carried out by a consolidated undrained triaxial test. A two-stage pouring method is adopted to pour samples, and the effects of dry density, cementation times, standing time, and confining pressure on the shear strength of cemented standard sand are emphatically analyzed. The relationship between cohesion, internal friction angle, and CaCO3 formation was analyzed. After the optimal curing conditions are obtained through the triaxial shear strength test, the erosion resistance model test is carried out. The effects of erosion angle, erosion flow rate, and erosion time on the erosion resistance of EICP-solidified sand were analyzed through an erosion model test. The results of triaxial tests show that the standard sand solidified by EICP exhibits strain softening, and the peak strength increases with the increase in initial dry density, cementation times, standing time, and confining pressure. When the content of CaCO3 increases from 2.84 g to 12.61 g, the cohesive force and internal friction angle change to 23.13 times and 1.18 times, and the determination coefficients reach 0.93 and 0.94, respectively. Erosion model test results indicate that the EICP-solidified sand dam has good erosion resistance. As the increase in erosion angle, erosion flow rate, and erosion time, the breach of solidified samples gradually becomes larger. Due to the deep solidification of sand by EICP, the development of breaches is relatively slow. Under different erosion conditions, the solidified samples did not collapse and the dam broke. The research results have important reference value and scientific significance for the practice of sand consolidation engineering in earth-rock dams.

Cavitation erosion on different metallic materials under high hydrostatic pressure evaluated with the spatially confined sonoluminescence.

Cavitation erosion is a general phenomenon in the fields of aviation, navigation, hydraulic machinery, and so on, causing great damage to fluid machinery. With the vast requirements in deep ocean applications, it is urgent to study the mechanism of cavitation erosion and the cavitation erosion resistance of different materials under high hydrostatic pressure to predict and avoid the effect of cavitation erosion. In this work, the spatially confined cavitation bubble cloud associated with Gaussian-like intensity distribution sonoluminescence (SL) was produced by a spherically focused ultrasound transducer with two opening ends near metallic plates under different hydrostatic pressures (0.1, 3, 6, and 10 MPa). The cavitation erosion effects on copper, 17-4PH stainless steel and tungsten plates were studied. Through coupling analysis towards the SL intensity distribution, the macro/micro morphology of cavitation erosion, and the physical parameters of different metallic materials (hardness, yield strength, and melting point), it is found that with increasing hydrostatic pressure, the erosion effect is intensified, the depth of cavitation pits increases, the phenomenon of melting can be observed on materials with relatively low melting points, and the cavitation erosion experienced an evolution process from high-temperature creep to fracture. This work has also established a method for the evaluation of materials' cavitation erosion resistance with measurable SL intensity distribution, which is promising to promote the designing and selection of anti-cavitation materials in deep-sea applications.

Experimental test and mechanism analysis of soil crust erosion resistance of rammed earth Great Wall in rainy season.

Rammed earth is a kind of cleaning material, widely used in all kinds of buildings in the world. The Great Wall of ancient China is a typical world cultural site built from rammed earth. The rammed earth Great Wall of Shanhaiguan is close to Bohai Bay, which has suffered from long-term erosion by rain, causing a series of problems such as soil loss, collapse and gully flushing. The protection materials of the rammed earth site have always puzzled scholars. However, during the rainy season, it was found that some of the walls at Xiaowan Gouge and Nantuzhuang Gouge in the Shanhaiguan Great Wall had unwashed traces, the soil surface of the walls was intact, and the anti-erosion ability of the walls was significantly higher than that of other places. In order to explore the reasons for its strong anti-erosion ability in the natural state of rammed earth wall, guide the protection of rammed earth Great Wall, and carry out different experimental tests to explore its anti-erosion reasons and internal mechanisms. Firstly, the characteristics of rammed soil were understood through the composition test of rammed soil, and the indoor and outdoor erosion test was carried out to determine that the anti-erosion reason was the protection of gray-green soil crust. The property and composition of soil crust were determined through the immersion test and genome sequencing. Finally, the protection mechanism of soil crust was analyzed by scanning electron microscopy.

Experimental Study on the Wind Erosion Resistance of Aeolian Sand Solidified by Microbially Induced Calcite Precipitation (MICP).

Microbially induced calcite precipitation (MICP) is an emerging solidification method characterized by high economic efficiency, environmental friendliness, and durability. This study validated the reliability of the MICP sand solidification method by conducting a small-scale wind tunnel model test using aeolian sand solidified by MICP and analyzing the effects of wind velocity (7 m/s, 10 m/s, and 13 m/s), deflation angle (0°, 15°, 30°, and 45°), wind erosion cycle (1, 3, and 5), and other related factors on the mass loss rate of solidified aeolian sand. The microstructure of aeolian sand was constructed by performing mesoscopic and microscopic testing based on X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). According to the test results, the mass loss rate of solidified aeolian sand gradually increases with the increase in wind velocity, deflation angle, and wind erosion cycle. When the wind velocity was 13 m/s, the mass loss rate of the aeolian sand was only 63.6%, indicating that aeolian sand has excellent wind erosion resistance. CaCO3 crystals generated by MICP were mostly distributed on sand particle surfaces, in sand particle pores, and between sand particles to realize the covering, filling, and cementing effects.

Synthesis of soybean soluble polysaccharide-based eco-friendly emulsions for soil erosion prevention and control.

This paper introduces the synthesis of an environmentally friendly emulsion that can be used as a soil anti-water erosion material. SSPS-g-P(BA-co-MMA-co-AA) emulsions were prepared using free radical copolymerization with soybean soluble polysaccharide (SSPS), acrylic acid (AA), butyl acrylate (BA), and methyl methacrylate (MMA). The structure, thermal stability, and morphology were characterized using FT-IR,TG,SEM, and particle diameter analysis. The resistance to water erosion, compressive strength and water retention of emulsion-treated loess/laterite was studied and germination tests were conducted. The results demonstrated that the duration of washout resistance of loess with 0.50 wt% emulsion exceeded 99 h, and the water erosion rate was 56.0 % after 72 h, while the water erosion rate of pure loess is 100.0 % after 4 min;the duration of washout resistance of laterite with 0.50 wt% emulsion exceeded 2 h, which was 8 times longer than pure laterite;The compressive strengths of 0.5 wt% emulsion-treated loess/laterite were 3.5 Mpa and 5.8 MPa, respectively, which were 7 and 9 times higher than that of pure soil. The plant seeds germinated normally half a month after planting. These findings suggest that emulsions can be used to control soil erosion without affecting the germination of plant seeds.

Processing-Microstructure-Properties of Columns in Thermal Barrier Coatings: A Study of Thermo-Chemico-Mechanical Durability.

Contemporary gas turbine engines rely on thermal barrier coatings (TBCs), which protect the structural components of the engine against degradation at extremely high operating temperatures (1300-1500 °C). The operational efficiencies of aircraft engines have seen significant improvement in recent years, primarily through the increase in operating temperatures; however, the longevity of TBCs can be potentially impacted by several types of degradation mechanisms. In this comprehensive study, a wide range of novel columnar suspension plasma sprayed (SPS) coatings were developed for their erosion, calcium-magnesium-aluminum-silicate (CMAS), and furnace cycling test (FCT) performance. Through a comprehensive investigation, the first of its kind, we achieved a range of SPS microstructures by modifying the spray parameters and measuring their microhardness, fracture toughness, column densities, and residual stresses using Raman spectroscopy. We were able to produce dendritic, lateral, branched, and columnar microstructures with a unique set of processing parameters. Coatings enhanced with a refined columnar microstructure, achieved by modulating the distance from the plasma torch, exhibited superior thermal cycling resilience. Conversely, the development of a columnar microstructure with dendritic branches, obtained by decreasing the robot's traversal speed during deposition, bolstered resistance to erosion and minimized damage from molten CMAS infiltration, thereby notably augmenting the coating's lifespan and robustness. The pursuit of the optimal columnar microstructure led to the conclusion that for each SPS coating, a general framework of optimization needs to be conducted to achieve their desired thermo-chemico-mechanical resistance as the properties required for TBCs are intertwined.

Enhancement of sewer sediment control and disruption of adhesive gelatinous sediment structure using low-dose calcium peroxide.

Large quantities of sediments in urban sewer systems pose significant risk of pipe clogging and corrosion. Owing to their gel-like structure, sewer sediments have strong resistance to hydraulic shear stress. This study proposed a novel approach to weaken the erosion resistance of sewer sediments by destroying viscous gel-like biopolymers in sediments with low doses of calcium peroxide (CaO2). After treatment with 10-50 mg g-1 TS of CaO2, the critical erosion shear stress was significantly reduced by 25.7%-59.9%. The sediment aggregates gradually disintegrated into small diameter particles with increasing CaO2 dosage. Further analysis showed that the strong oxidizing and alkaline environment induced by CaO2 treatment led to cell lysis and changes in the composition and property of extracellular polymeric substances (EPS). After CaO2 treatment, aromatic proteins and humic acid-like substances associated with adhesion translocated from the inner EPS layers to outer layers while being disintegrated into small organic molecules. Concomitantly, CaO2 treatment disrupted the main functional groups (-OH, COO-, C-N, CO, and CN) in inner EPS layers, thus weakening EPS adhesion. Analysis of protein secondary structure and zeta potential reflected the reduced aggregation capacity of sediment microorganisms and loosening of sediment structure after CaO2 treatment. Thus, CaO2 treatment facilitated fragmentation and disaggregation of the gelatinous structure of sewer sediments. Such green strategy decreased the cost of sewer sediment disposal by 42.10-68.95% when compared to water flushing, and it would improve the self-cleaning capacity of sewer system and efficiency of dredging equipment.

Microscopic deposition-property relationships in microbial-induced consolidation of coal dusts.

In recent years, the preparation of new microbial dust suppressants based on microbial induced carbonate precipitation (MICP) technology through enriched urease-producing microbial communities has become a new topic in the field of coal dust control. The deposition of CaCO3 was the key to suppress coal dust. However, deposition characteristics in the field is not sufficient and the relationship between deposition characteristics and erosion resistance is not clear, which hinders the development of engineering application of new microbial dust suppressant. Therefore, based on X-CT technology, this paper observed and quantified micro-deposition of bio-consolidated coal dust with different calcium sources. Furthermore, a conceptual framework for deposition was proposed and its correlation with erosion resistance was revealed. The results showed that CaCO3 induced by calcium chloride and calcium lactate was aggregate deposited. Aggregate deposited CaCO3 was small in volume, showed the distribution of aggregation in the central area and loose outside, and mosaiced pores. CaCO3 induced by calcium nitrate was surface deposition due to attached biomass. Surface deposition was mostly large volume CaCO3 expanding from the inside out, which could cover coal dust to a high degree and completely cemented pores. In addition, the threshold detachment velocity of coal dust cemented by surface deposition was increased by 17.6-19.1% compared to aggregate deposition. This depended on the abundance and strength of CaCO3 bonding between coal dust particles under different deposition. The two-factor model based on porosity and CaCO3 coverage can well express relationship between erosion resistance and depositional characteristics. Those results will help the engineering application of MICP technology in coal dust suppression.

The Influence of Heat Aging Treatments on the Cavitation Erosion Behavior of a Type 6082 Aluminum Alloy.

It is known that a number of parts that operate in liquid media, such as the propellers of motorboats and pleasure river vessels, as well as the rotors of household pumps and the radiators and pumps in the cooling system of motor vehicles are made, as a rule, of aluminum-based alloy. Research during maintenance leads to the conclusion that, in certain operating conditions, due to the turbulent character of the flow, with pressure drops to below the vaporization level, it inevitably reaches the threshold of cavitation, which manifests itself through its effects, especially through erosion. To increase the lifetime, these alloys are currently subjected to techniques to improve the structure's resistance to the cyclic stresses of cavitational microjets. Among these techniques are volumetric heat treatments, which lead to changes in the microstructure and mechanical property values, with an effect on the behavior and resistance to cavitation erosion. This paper studies the influence of heat aging treatments on the cavitation erosion behavior of an aluminum alloy type 6082, in the cast state. The heat treatments applied were 140 °C/1 h, 12 h, 24 h and 180 °C/1 h, 12 h, 24 h. The MDEmax and MDERs parameters were determined and a correlation could be made between the values of the mechanical-resilient characteristics and the resistance to cavitation erosion in the case of aluminum alloy 6082.

Effects of several polymeric materials on the improvement of the sandy soil under rainfall simulation.

Poor cementation between soil particles is a fundamental cause of soil erosion and desertification. In recent decades, many polymers have been used to cement soil particles and improve the physical and chemical properties of soils. The contributions of polymers with different structures and functional groups to soil improvement vary considerably. In this study, a mixture comprising polyacrylamide (PAM), sodium polyacrylate (PAAS), hydroxypropyl methylcellulose (HPMC), and polyvinyl alcohol (PVA) was investigated to meet the requirements of soil water retention, erosion resistance, and plant growth. The results showed that the time required for the modified soil to reach drought conditions was extended by 4-7 days. The PAM/HPMC, PAM/PVA and PAM/PAAS experimental groups reduced the erosion rate by 99.57%, 98.3% and 96.38%, respectively, compared to that of the control group. The belowground plant biomass was significantly increased by PAM/HPMC, PAM/PAAS, and PAM/PVA, with increases of 115.92%, 145.23%, and 205.67%, respectively. HPMC contributed more to the soil erosion resistance and water-holding capacity, PAAS improved the soil porosity substantially, and PVA significantly increased the plant biomass. The rigid structures of the polymer chains enhanced the structural stability of the soil, and the hydrophilic functional groups increased the hydrophilicity of the amended soil. This study indicates different polymers that may be used to improve soil properties.

Preparation and molecular simulation of an environmentally friendly dust-fixing agent based on chitosan-gelatin.

In order to solve the hazard of coal mine dust, a dust-fixing agent (GC-TG-JFC) was prepared with gelatin, chitosan, octadecanol polyoxyethylene ether, and glutamine transaminase. The experimental conditions and the formulation were optimized by response surface method. The ratio of gelatin, chitosan, octadecanol polyoxyethylene ether, and glutamine transaminase was 0.405:0.211:0.095:0.286 and the dilution ratio was 1:30. The results of product performance test showed that the dust fixation rate could reach 99.95% when the wind speed was 9 m/s. The viscosity of the diluted solution was 42.5 mPa·s. The Forcite module in Materials studio software was used to analyze and calculate the radial distribution concentration, diffusion coefficient, and binding energy of the solution. The results showed that GC-TG-JFC migrated more water molecules to the surface of coal through the action of van der Waals force and hydrogen bond. In addition, the binding energy of water molecules increased and the diffusion coefficient decreased, which improved the binding ability of water molecules with coal. It could be found that GC-TG-JFC had good dust fixation performance by combining experiment and molecular dynamics method.

Corrosion Resistance of CeO2-GO/Epoxy Nanocomposite Coating in Simulated Seawater and Concrete Pore Solutions.

Reinforced concrete structures in the marine environment face serious corrosion risks. Coating protection and adding corrosion inhibitors are the most economical and effective methods. In this study, a nano-composite anti-corrosion filler with a mass ratio of CeO2:GO = 4:1 was prepared by hydrothermally growing cerium oxide on the surface of graphene oxide. The filler was mixed with pure epoxy resin at a mass fraction of 0.5% to prepare a nano-composite epoxy coating. The basic properties of the prepared coating were evaluated from the aspects of surface hardness, adhesion grade, and anti-corrosion performance on Q235 low carbon steel subjected to simulated seawater and simulated concrete pore solutions. Results showed that after 90 days of service, the corrosion current density of the nanocomposite coating mixed with corrosion inhibitor was the lowest (Icorr = 1.001 × 10-9 A/cm2), and the protection efficiency was up to 99.92%. This study provides a theoretical foundation for solving the corrosion problem of Q235 low carbon steel in the marine environment.

Sewer sediment adhesion reduction and hydraulic floating promotion by alkaline treatment.

Deposition of sediment in sewers decreased flow capacity, with harmful gases and pipe erosion. Sediment floating and removal remained challenges due to its gelatinous structure, which induced strong erosion resistance. This study proposed an innovative alkaline treatment for destructuring gelatinous organic matters and improving hydraulic flushing capacity of sediments. At the optimal pH 11.0 condition, the gelatinous extracellular polymeric substance (EPS) and microbial cells were disrupted, with numerous outward migration and solubilization of proteins, polysaccharides and humus. The aromatic protein solubilization (tryptophan-like and tyrosine-like proteins) and humic acid-like substance deconstruction were the major driving factors for sediment cohesion reduction, which disintegrated the bio-aggregation and increased the surface electronegativity. Meanwhile, the variations of functional groups (CC, CO, COO-, CN, NH, C-O-C, C-OH, OH) also contributed to the interaction breakage and glutinous structure disruption of sediment particles. It was found that the rising pH conditions reduced sediment adhesion and promoted particle floating. Solubilizations of total suspended solids and volatile suspended solids were increased by 12.8 and 9.4 times, respectively, while the sediment adhesion was reduced by 3.8 fold. The alkaline treatment greatly improved sediment erosion and flushing capacities under shear stress of gravity sewage flow. Such sustainable strategy only cost 36.4 CNY per sewer meter length, which was 29.5-55.0 % of the high-pressure water jet flushing and perforated tube flushing approaches.

Degradation and Protection of Materials from Cavitation Erosion: A Review.

The phenomena of cavitation and cavitation erosion affect hydraulic machines, increasing their maintenance costs. Both these phenomena and also the methods of preventing the destruction of materials are presented. The compressive stress in the surface layer created from the implosion of cavitation bubbles depends on the aggressiveness of the cavitation, which in turn depends on the test device and test conditions, and also affects the erosion rate. Comparing the erosion rates of different materials tested using different tests devices, the correlation with material hardness was confirmed. However, no one simple correlation was obtained but rather several were achieved. This indicates that in addition to hardness, cavitation erosion resistance is also affected by other properties, such as ductility, fatigue strength and fracture toughness. Various methods such as plasma nitriding, shot peening, deep rolling and coating deposition used to increase resistance to cavitation erosion by increasing the hardness of the material surface are presented. It is shown that the improvement depends on the substrate, coating material and test conditions, but even using the same materials and test conditions large differences in the improvement can be sometimes gained. Moreover, sometimes a slight change in the manufacturing conditions of the protective layer or coating component can even contribute to a deterioration in resistance compared with the untreated material. Plasma nitriding can improve resistance by even 20 times, but in most cases, the improvement was about two-fold. Shot peening or friction stir processing can improve erosion resistance up to five times. However, such treatment introduces compressive stresses into the surface layer, which reduces corrosion resistance. Testing in a 3.5% NaCl solution showed a deterioration of resistance. Other effective treatments were laser treatment (an improvement from 1.15 times to about 7 times), the deposition of PVD coatings (an improvement of up to 40 times) and HVOF coatings or HVAF coatings (an improvement of up to 6.5 times). It is shown that the ratio of the coating hardness to the hardness of the substrate is also very important, and for a value greater than the threshold value, the improvement in resistance decreases. A thick, hard and brittle coating or alloyed layer may impair the resistance compared to the untreated substrate material.

Humic-Based Polyelectrolyte Complexes for Dust Suppression.

The present study proposes a novel application of humic substance-aminosilsesquioxane polyelectrolyte complexes (HS-ASQ) as dust suppressants. These complexes are synthesized through the reaction between humic substances (HS) and 3-aminopropyltriethoxysilane (APTES) in aqueous solution, resulting in the formation of active silanol groups that can bind to mineral surfaces and condense, forming gels. The HS-ASQ compositions were found to have a high sorption capacity for dust particles and could form coatings on their surface without cementing the dust, making them potentially useful for environmental applications. The viscosity of the HS-ASQ compositions can be controlled by adding carboxymethylcellulose (CMC), which also enhances their dust suppression abilities. Different compositions of HS-ASQ were synthesized by varying the proportions of APTES and CMC, and dust treated with these samples was assessed for its resistance to wind erosion using a laboratory-scale setup. Treatment with the HS-ASQ composition resulted in substantial reductions in PM10 and PM2.5 concentrations (particulate matter with aerodynamic diameters of 10 µm and 2.5 µm, respectively) of up to 77% and 85%, respectively, compared to the control.

Solid Particle Erosion Behavior on the Outer Surface of Basalt/Epoxy Composite Pipes Produced by the Filament Winding Technique.

Basalt/epoxy composite pipes in a [±55]4 winding configuration were produced on CNC filament winding machines (10 N fiber tension and ~11 mm bandwidth). In the experiments, a 34 m/s impact velocity was set using the double-disc method, and five different particle impingement angles (30, 45, 60, 75, and 90°) were used to determine the erosive effect on the outer surfaces of filament wound composite pipes under the influence of 600 µm erodent particles with angular geometry in the test set, complying with the ASTM G76-95 standard. The winding patterns in the lamina (±55 angle-ply laminate region) and zigzag (±55 zigzag region) regions of BFR/EP pipes were determined to have significant effects on solid particle erosion resistance, as evidenced by the SEM images.

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Soil microbial biofilms (SMBs) are a biological community of soil bacteria and their accumulative extracellular polymeric substances (EPS), which are the initial status and the most important components of biological soil crusts. SMBs, as the most common mode of soil bacterium survival, not only greatly contribute to the survival of free-living cells, but also stick to soil particles and roots, performing a variety of important ecological functions. Based on the structure and composition analysis of SMBs, we gave a summary of eco-physiological functions of SMBs involving soil quality and plant health. SMBs have higher metabolic activity than free-living cells. It promotes EPS secretion and organic turnover, which is important for soil fertility, pollutant decomposition, and aggregate formation. SMBs help improve plant nutrient utilization and stress resistance through the synergy of microorganisms, promotion of plant growth, promoting substance secretion and immobilization of EPS. In the future, it will be critical to uncover the micro-mechanisms underlying SMBs' eco-physiological functions and to screen functional soil bacterium strains.

Polyvinyl acetate-based soil stabilization for rock slope ecological restoration.

External-soil spray seeding (ESSS) is a method often used for the ecological restoration of bare rock slopes. However, the direct use of ESSS is normally less satisfactory due to the erosion of sprayed soil and low survival rate of the plants on rock slopes. This study proposes a novel approach to addressing this issue through the combined use of ESSS with polyvinyl acetate (PVA) based soil stabilization. The PVA solutions are added to the soil to stabilize soil and improve soil strength while possessing high water and nutrient retention favorable for plant growth. A series of experimental tests on the mechanical properties, water stability, erosion resistance, water retention, and plant growth of the PVA-stabilized soil were conducted to assess the efficacy of the proposed method. The results showed that the proposed method could be promising for rock slope ecological restoration. A proper curing time (e.g., >3 days) was required to achieve beneficial effects of PVA on the soil properties. A shorter curing time would otherwise result in the decrease in the strength with the increased PVA content. It was found that the optimum PVA content was 3% for achieving the maximum water stability, erosion resistance, water retention, and plant growth. The cohesion increased by up to 50% and the internal friction angle increased by 3.5° compared to the natural soil. The disintegration rate of the stabilized soil was generally < 3e-3%/min. The maximum reduction in erosion was up to 83% when the PVA content ≥3%. The mechanisms behind the findings are also discussed.

Experimental Investigation on the Breaching Process of Landslide Dams with Differing Materials under Different Inflow Conditions.

Landslide dams are dangerous because the outburst floods produced by dam failures seriously threaten life and property downstream. In this study, a series of physical flume tests were conducted to investigate the breaching process of landslide dams with fine-grained, well graded, and coarse-grained material under different inflow conditions. The effects of dam material and inflow discharge on the breach development, outflow discharge and erosion characteristics were studied. The erosion resistance of materials and lateral collapses were also discussed. Experimental results reveal that the whole breaching process is determined by the water-sediment interaction. For the fine-grained dams, a general constant downstream slope angle is maintained during the breaching process. For the well-graded dams, a step-pool structure is generated due to the scarp erosion. For the coarse-grained dams, they can remain stable under normal circumstances but fail by overtopping in a short duration under the extreme inflow condition. The final breach of the dam with higher fine content or larger inflow discharge is deeper and narrower. In addition, many fluctuations are observed in the changing curve of the erosion rates along the flow direction for the well-graded and coarse-grained dams. The erosion resistance of materials increases along the flow direction, which needs to be further considered in physically based breach models. Furthermore, the lateral collapse is affected by the dam material instead of inflow discharge. The lower fine content causes more lateral collapses with smaller volumes.

Strengthened erosion resistance of compacted bentonite by layered double hydroxide: A new electrostatic interaction-based approach.

For the geological repository of high-level radioactive waste (HLW) built in granitic host rock，the control of buffer material (compacted bentonite) erosion and subsequent loss caused by groundwater in granite fissures is an unresolved problem of major concern. We propose here new insight into enhancing the erosion resistance of compacted bentonite by means of its electrostatic interaction with oppositely-charged layered double hydroxide (LDH). The interaction between bentonite and LDH was studied by dropwise addition of colloidal LDH into colloidal bentonite suspension, during which the variation in electrical conductivity, zeta potential and particle size proved a strong interaction between these two materials. Interestingly, in addition to their aggregation, intercalated structures of LDH and montmorillonite were found in the composite (BEN@LDH) by a combined characterization of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM), and were confirmed by density functional theory (DFT) calculation. Colloid generation of compacted BEN@LDH under ultrasonic conditions is negligible comparing with that of compacted bentonite, indicating a significantly higher erosion resistance. Besides, a small amount of LDH by mechanically mixing with bentonite (mass ratio 1:99) can also effectively improve the erosion resistance of compacted bentonite. Moreover, BEN@LDH displayed stronger retention performance towards U(VI) and Se(IV) than bentonite under near-neutral/weakly alkaline conditions. Our results indicate that LDH is a promising additive in compacted bentonite, and this approach may be extended to common geotechnical structures built with clays and soils.