Saturated Layer Research Articles

An Mn-Enriched Interfacial Layer for Reversible Aqueous Mn Metal Batteries.

Aqueous manganese metal batteries have emerged as promising candidates for stationary storage due to their natural abundance, safety, and high energy density. However, the high chemical reactivity and sluggish migration kinetics of the Mn metal anode induce a severe hydrogen evolution reaction (HER) and dendrite formation, respectively. The situation deteriorates in the low-concentration electrolyte especially. Here, we propose a novel approach to construct an Mn-enriched interfacial layer (Mn@MIL) on the Mn metal anode surface to address these challenges simultaneously. The Mn@MIL acts as a physical barrier to not only suppress HER but also accelerate the Mn2+ diffusion kinetics through the Mn2+ saturated interfacial layer to inhibit dendrite growth. Therefore, in the low-concentration electrolyte (1 M MnCl2), the Mn||Mn symmetric cells and Mn||V2O5 full cells with high mass loading demonstrate promising cycling stability with minimal polarization and parasitic reactions, making them more suitable for practical applications in a smart grid.

Synthesis of Polyether Block Copolymers from 1,2-Epoxybutane and AEOn and Comparative Study of Physicochemical and Application Properties before and after the Synthesis.

In this study, the AEOnBO2 series of block polyoxybutenol ethers was synthesized by combining the AEO series of polyoxyethylene and preparing 1,2-epoxybutane (BO) block polyether using a semicontinuous method. The synthesis was performed by HPLC, MALDI-TOF-MS, FT-IR, and 1H NMR for structural analysis. The interaction parameters and surface tension of the systems before and after synthesis were studied using surface tension meter. The diffusion process of the systems before and after synthesis was studied using a KRÜSS bubble pressure tensiometer. The surfactant properties of AEOn and AEOnBO2 were evaluated by static and dynamic surface tension measurements. Each system formed a saturated adsorption layer in a water solution. The critical micelle concentration decreased dramatically after the introduction of BO groups, and the diffusion-adsorption process was consistent with the kinetic mechanism of hybrid diffusion. The microscopic self-assembled aggregate micellar behavior of all the systems was investigated using DLS, TEM, and SEM. The micellization process in all systems was spontaneous and enthalpy-driven, forming spherical aggregates, with the BO block reducing the aggregate diameter of the feedstock from 220.06 nm to about one-third of 80.02 nm. In addition, the dynamic contact angle, application, and physicochemical properties such as foaming and foam stabilization of each system were investigated. The contact angle was reduced from 70 to 50° at 120 s of stabilization, with a foam volume of 80 mL in all systems at 200 s. However, the AEOnBO2 showed accelerated foam decay at 500 s, with an increase in the contact angle from 70 to 50° at 200 s, but the AEOnBO2 showed accelerated foam decay at 500 s, with a decrease in the contact angle from 70 to 50° at 120 s stabilization. At 200 s, the foam volume of all systems was 80 mL, but AEOnBO2 showed an accelerated foam decay process, which shows that the BO group can accelerate the foam decay, and the comparative results show that the BO group can also optimize other application properties and physicochemical properties.

Linear and nonlinear stability of double diffusive convection in a micropolar fluid saturated porous layer with magnetic field and throughflow effects

The linear and nonlinear stability of double-diffusive convection in a porous layer saturated with micropolar fluid is examined. A transverse magnetic field is applied to the flow together with vertical throughflow. The normal mode technique is employed for linear stability analysis, whereas the energy method is used for nonlinear stability analysis. The resulting eigenvalue problems corresponding to linear and nonlinear stability theories are solved numerically by employing the bvp4c routine in MATLAB 2022(b). The critical thermal Rayleigh numbers for both linear and nonlinear analyses are computed for the different values of the governing parameters and presented graphically. A comparison is made between linear and nonlinear stability results. It is observed that the flow is more stable whenever a magnetic field is added to the flow, although the subcritical instability region also slightly increases. Increasing the Darcy number, Lewis number, coupling number, and absolute value of the throughflow parameter destabilizes the flow. On the other hand, raising the porosity of the medium and micropolar parameters stabilizes the flow. Furthermore, there is no subcritical gap in the absence of the throughflow effect, which is a good agreement between the linear and nonlinear thresholds.

The use of R code for modeling and simulation of 2-D contaminant migration through a soil for the pulse source

<p>In this study, based on an existing analytical solution for the two-dimensional transport of contaminants in a saturated soil layer, for the pulse source, the R program code was developed. The simulation is used to obtain the profiles of contaminant concentration, for a steady groundwater velocity, as a function of distance from the source and time. The problem is analytically solved by leveraging the similarity between the Gaussian (normal) distribution and contaminant concentration distribution, the development of the analytical model (i.e., solution of partial differential equation) by using this similarity is explained step by step since it may be of interest to researchers. Contaminant propagation is modeled using R software, which helps to understand how contaminants migrate through a saturated soil layer. This approach aids in comprehending the mechanisms and spatial dynamics of contaminant dispersion, facilitating the prediction and management of soil and groundwater contamination. The provided R code can be altered for different parameters and time intervals.</p>

The use of R code for modeling and simulation of 2-D contaminant migration through a soil for the pulse source

<p>In this study, based on an existing analytical solution for the two-dimensional transport of contaminants in a saturated soil layer, for the pulse source, the R program code was developed. The simulation is used to obtain the profiles of contaminant concentration, for a steady groundwater velocity, as a function of distance from the source and time. The problem is analytically solved by leveraging the similarity between the Gaussian (normal) distribution and contaminant concentration distribution, the development of the analytical model (i.e., solution of partial differential equation) by using this similarity is explained step by step since it may be of interest to researchers. Contaminant propagation is modeled using R software, which helps to understand how contaminants migrate through a saturated soil layer. This approach aids in comprehending the mechanisms and spatial dynamics of contaminant dispersion, facilitating the prediction and management of soil and groundwater contamination. The provided R code can be altered for different parameters and time intervals.</p>

Boron Delta-Doping in Si : B Stacks By RP-CVD Epitaxy

Low resistivity materials are required for advanced MOS or equivalent technologies. High boron in-situ doped Si epitaxy is known to create defects that increase the resistivity. Boron delta-doping (Si:B epitaxy alternating with boron saturation layers) is a potential solution to overcome this limitation. Using the delta-doping process at 750 °C in a Reduced Pressure Chemical Vapor Deposition reactor, a resistivity two times lower than that without delta-doping (8.9x10-4 Ω.cm and 1.86x10-3 Ω.cm respectively) was achieved. SIMS characterization measured a total boron concentration of 3.3x1021 at.cm-3. However, the delta-doping processes , as a function of the soaking volume (product of B2H6 flow and saturation time), resulted in low crystal quality and highly stressed layers. Moreover, thin layers were observed by TEM likely due to the formation of the SiBx phase at each saturation layer. For an equivalent soaking volume, a better crystal quality was obtained with a high B2H6 flow and short saturation time.

Insight into using multi-omics analysis to elucidate nitrogen removal mechanisms in a novel improved constructed rapid infiltration system: Functional gene and metabolite signatures

In this study, a laboratory-scale improved constructed rapid infiltration (imCRI) system with non-saturated and saturated layers was constructed, and corn cobs as solid carbon source were added to the saturated layer to enhance the removal of nitrogen. Combined analyses of metagenomics and metabolomics were conducted to elucidate the nitrogen removal mechanism in the imCRI system. The results showed that the hydraulic load significantly influenced the treatment performance of the imCRI system, and a hydraulic load of 1.25 m3/(m2⋅d) was recommended. Under optimal conditions, the imCRI system using simulated wastewater achieved average removal efficiencies of 97.8 % for chemical oxygen demand, 85.7 % for total nitrogen (TN), and 97.6 % for ammonia nitrogen. Metagenomic and metabolomic analyses revealed that besides nitrification and denitrification, dissimilatory nitrate reduction to ammonium (DNRA), anammox, etc., are also involved in nitrogen metabolism in the imCRI system. Although nitrification was the predominant pathway in the non-saturated layer, aerobic denitrification also occurred, accounting for 22.59 % of the TN removal. In the saturated layer, nitrogen removal was attributed to synergistic effects of denitrification, DNRA and anammox. Moreover, correlation analysis among nitrogen removal, functional genes and metabolites suggested that metabolites related to the tricarboxylic acid cycle generated from the glycolysis of corn cobs provided sufficient energy for denitrification. Our results can offer a promising technology for decentralized wastewater treatment with stringent nitrogen removal requirements, and provide a foundation for understanding the underlying nitrogen transformation and removal mechanism.

Advantages of Direct Laser Writing for Enhancing the Resolution of Diffractive Optical Element Fabrication Processes

A technology for direct laser writing of code sequences on modulation disks has been developed and implemented, ensuring high accuracy and reliability in the process of forming structural elements. The main advantages of applying direct laser writing compared to contact lithography for forming submicron-sized elements have been demonstrated. The proposed technology is characterized by high resolution and flexibility in configuring the parameters of the optical recording system, making it suitable for a wide range of applications in micro-optics. Direct optical writing is presented as a promising approach for enhancing the resolution of optical systems used in recording submicron-sized diffractive optical elements, as this technology enables the creation of complex optical structures. Additionally, a detailed classification of current approaches for further increasing the resolution of the optical recording system was conducted, including the application of a saturated absorber layer on the photosensitive surface, the use of a laser beam with intensity modeled by a Bessel function, and the synthesis of photosensitive materials with optimized exposure characteristics, ensuring high efficiency and accuracy in the process of direct laser writing.

Buoyancy-driven heat transfer and entropy analysis of a hydromagnetic GO-Fe3O4/H2O hybrid nanofluid in an energy storage enclosure partially filled with non-Darcy porous medium under an oblique magnetic field

Purpose Thermal energy storage systems use thermal energy to elevate the temperature of a storage substance, enabling the release of energy during a discharge cycle. The storage or retrieval of energy occurs through the heating or cooling of either a liquid or a solid, without undergoing a phase change, within a sensible heat storage system. In a sensible packed bed thermal energy storage system, the structure comprises porous media that form the packed solid material, while fluid occupies the voids. Thus, a cavity, partially filled with a fluid layer and partially with a saturated porous layer, has become important in the investigation of natural convection heat transfer, carrying significant relevance within thermal energy storage systems. Motivated by these insights, the current investigation delves into the convection heat transfer driven by buoyancy and entropy generation within a partially porous cavity that is differentially heated, vertically layered and filled with a hybrid nanofluid. Design/methodology/approach The investigation encompasses two distinct scenarios. In the first instance, the porous layer is positioned next to the heated wall, while the opposite region consists of a fluid layer. In the second case, the layers switch places, with the fluid layer adjacent to the heated wall. The system of equations for fluid and porous media, along with appropriate initial and boundary conditions, is addressed using the finite difference method. The Tiwari–Das model is used in this investigation, and the viscosity and thermal conductivity are determined using correlations specific to spherical nanoparticles. Findings Comprehensive numerical simulations have been performed, considering controlling factors such as the Darcy number, nanoparticle volume fraction, Rayleigh number, bottom slit position and Hartmann number. The visual representation of the numerical findings includes streamlines, isotherms and entropy lines, as well as plots illustrating average entropy generation and the average Nusselt number. These representations aim to provide insight into the influence of these parameters across a spectrum of scenarios. Originality/value The computational outcomes indicate that with an increase in the Darcy number, the addition of 2.5% magnetite nanoparticles to the GO nanofluid results in an enhanced heat transfer rate, showing increases of 0.567% in Case 1 and 3.894% in Case 2. Compared with Case 2, Case 1 exhibits a 59.90% enhancement in heat transfer within the enclosure. Positioning the porous layer next to the partially cooled wall significantly boosts the average total entropy production, showing a substantial increase of 11.36% at an elevated Rayleigh number value. Positioning the hot slit near the bottom wall leads to a reduction in total entropy generation by 33.20% compared to its placement at the center and by 33.32% in comparison to its proximity to the top wall.

Impact of forced aeration on vertical flow treatment wetland performances for combined sewer overflow

Combined Sewer Overflow Treatment Wetlands (CSO wetlands) are designed to remove pollutants under stochastic events with variable hydraulic loads. Upgrading them with forced aeration promises to increase the effectiveness and resilience of the treatment. We have tested two vertical CSO wetlands with forced aeration (CSOa and CSOb) to understand the effects of aeration on CSO treatment. Both filter beds have 0.95 and 0.80 m of saturated layer. CSOa uses gravel as top filtering layer, while CSOb utilizes sand and an additional transition layer. Tracer tests were conducted in both filters with and without aeration to assess the impact of aeration on hydraulic performance. CSOa operated with four different aeration conditions, with the optimal condition tested on both filters for comparison. Samples were taken for analysis of global parameters and the redox potential was monitored online. In the tracer test, CSOa allowed to observe the mixing impact of aeration, which avoids any preferential path when influent entered the filter. The addition of a sand layer at the surface (CSOb) allows for a more even distribution of water on the top, which limits preferential flows when aeration is off. In both filters, the results showed that aeration increased the residence time and mixing degree (NTIS <3). Testing different aeration strategies revealed the dependence of dissolved pollutant removal on oxygen supply. In CSOa, the median outlet concentration varied from 23 to 6.4 mg.L−1 in TSS, 153 to 32 mg.L−1 total COD (CODt), 124 to 20 mg.L−1 soluble COD (CODs) and 5 to 2.5 mg.L−1 NH4-N according to aeration strategy. The lower outlet concentrations were always under the highest aeration condition. Under the optimal condition (75 min on/15 min off), median removal of CSOa was 97% TSS, 85% CODt, 78% CODs and 75% NH4-N. Besides COD and TSS, outlet concentration and removal efficiency did not significantly differ between CSOa and CSOb. Pollutant removal demonstrated a linear correlation with organic surface load. Overall, forced aeration in CSO-TW distinctly affected filter dynamics and improved its performance.

The impact of rotation on the onset of cellular convective movement in a casson fluid saturated permeable layer with temperature dependent thermal conductivity and viscosity deviations

In this effort, we examined the impact of rotation on the arrival of cellular convective motion in a Casson fluid saturated permeable layer with temperature dependent thermal conductivity and viscosity deviations. The problem is important to cellular foams prepared from plastics, ceramics, and metallic where radiation conductivity is revealed as a power function of temperature. The altered Darcy model is used to characterize the rheological performance of Casson fluid flow in permeable medium. The approximate analytical solution and numerical solution correct to one decimal place are presented utilizing the Galerkin method. The analysis reveals that the influence of thermal conductivity disparity parameter and the rotation is to delay the convective motion whereas; the viscosity disparity parameter and the Casson parameter have dual impact on the convective motion in the presence of rotation. The range of the convective cell drops with increasing the thermal conductivity disparity parameter, the viscosity disparity parameter, the Casson parameter and rotation parameter. In the absence of rotation, the range of the convective cell does not depend on the Casson parameter and the viscosity disparity parameter. Further, the existing results are compared with the existing literature under the particular case of this study.

Shallow-landslide stability evaluation in loess areas according to the Revised Infinite Slope Model: a case study of the 7.25 Tianshui sliding-flow landslide events of 2013 in the southwest of the Loess Plateau, China

Abstract. The occurrence of shallow loess landslides induced by prolonged heavy rainfall is prevalent in loess-dominated regions, often leading to property damage, human casualties, and sediment pollution. Developing an accurate prediction model for shallow landslides in loess areas is crucial for effective landslide mitigation. In 2013, prolonged heavy rains from 19–25 July triggered mass sliding-flow loess landslides in Tianshui, China. Landslide data, along with the characteristics of the sliding-flow loess landslides, were obtained through extensive field investigations and remote sensing interpretations. The sliding-flow loess landslide event demonstrated clustering, high density, small areas, and long travel distance. The depth of the sliding surface is correlated with the saturated layer resulting from rainfall infiltration; it is typically less than 2 m deep and negatively correlated with slope steepness. Based on the common characteristics of shallow loess landslides, the mechanisms involved in the sliding-flow landslide are proposed. The Revised Infinite Slope Model (RISM) was introduced using an equal differential unit method to address deficiencies when the safety factor remains constant or increases with increasing slope greater than 40°, as calculated using the Taylor slope infinite model. The relationship between the critical depth and the slope of the shallow loess landslide was determined. The intensity–duration (I–D) prediction curve of the rainfall-induced shallow loess landslides for different slopes was constructed and combined with the characteristics of rainfall infiltration for use in forecasting regional shallow loess landslides. Additionally, the influence of loess strength on the shallow loess landslide stability was analyzed. The shallow loess landslide stability responds to slope and cohesion but is not sensitive to the internal friction angle.

Investigation of Magneto-convection in Viscoelastic Fluid Saturated Anisotropic Porous Layer Under Local Thermal Non-equilibrium Condition

The problem of magneto-convection in viscoelastic fluid saturated anisotropic porous layer under local thermal non-equilibrium (LTNE) effect is investigated. Extended Darcy model with time derivative term for viscoelastic fluid of the Oldroyd type with an externally imposed vertical magnetic field is used to model the momentum equation. The entire investigation has been split into two parts: (i) linear stability analysis (ii) weakly non-linear stability analysis. We perform normal mode technique to examine linear stability analysis while truncated representation of Fourier series method is used for weakly non-linear stability analysis. The onset of convection is set in through oscillatory rather than stationary mode due to competition between the processes of thermal, magnetic effect and viscoelasticity. A comparative study between anisotropic and isotropic porous medium is made as a function of Q (Chandrasekhar number), 𝛤 (non dimensional inter phase heat transfer coefficient), 𝜆1 (Relaxation time) and λ2 (Retardation time). Apart from this, Q, 𝛤 and λ2 stabilize the system in oscillatory case while 𝜆1 destabilize the system. Furthermore 𝜉 (mechanical anisotropic parameter), 𝜂s (thermal anisotropic parameter for solid phase), destabilizes the system and 𝜂f (thermal anisotropic parameter for fluid phase) stabilizes the system. The effect of Q, 𝜆1, λ2, 𝛤, 𝜉, 𝜂f and 𝜂s on heat transfer is also examined.

Study on seismic response of liquefiable soil-pile group considering pile cap and soil contact

In this paper, based on the centrifuge test of liquefied soil-pile foundation system, a numerical model of liquefied soil-pile foundation-structure system is modelled by using OpenSees platform. In the simulation model, the friction effect between liquefied ground and low pile cap is considered, and the method of establishing virtual nodes is used to deal with the non-linear contact between liquefiable soil and low pile cap. The rationality and effectiveness of the numerical simulation method adopted in this paper has been verified and evaluated by comparing with the results of centrifuge experiments. A typical liquefaction soil-pile integrated finite element model is modelled using validated numerical simulation methods. The law of seismic response of the pile foundation system with different embedding depths of pile cap, different contact modes between the pile cap and saturated sand, and the thickness of the overlying saturated loose sand layer are discussed. The results show that the pile cap and pile foundation in the high pile cap system show higher seismic response characteristics than the other three low pile cap system conditions; Under the condition of different contact modes between the pile cap and the surrounding saturated sand, the peak bending moment and residual displacement of the pile foundation calculated by the bond contact are larger than calculated by the friction contact, and the deformation of pile is more significant. By comparing the working conditions of different thicknesses of overlying saturated loose sand layer, it is found that the degree of liquefaction in shallow soils is less affected by thickness of the saturated loose sand. As the thickness of saturated loose sand layer increases, the peak bending moment and residual displacement at the top of the pile also gradually increase. The change of peak bending moment at the soil interface is more obvious.

Developing a tile drainage module for the Cold Regions Hydrological Model: lessons from a farm in southern Ontario, Canada

Abstract. Systematic tile drainage is used extensively in poorly drained agricultural lands to remove excess water and improve crop growth; however, tiles can also transfer nutrients from farmlands to downstream surface water bodies, leading to water quality problems. Thus, there is a need to simulate the hydrological behaviour of tile drains to understand the impacts of climate or land management change on agricultural surface and subsurface runoff. The Cold Regions Hydrological Model (CRHM) is a physically based, modular modelling system developed for cold regions. Here, a tile drainage module is developed for CRHM. A multi-variable, multi-criteria model performance evaluation strategy was deployed to examine the ability of the module to capture tile discharge under both winter and summer conditions (NSE &gt; 0.29, RSR &lt; 0.84 and PBias &lt; 20 for tile flow and saturated storage simulations). Initial model simulations run at a 15 min interval did not satisfactorily represent tile discharge; however, model simulations improved when the time step was lengthened to hourly but also with the explicit representation of capillary rise for moisture interactions between the rooting zone and groundwater, demonstrating the significance of capillary rise above the saturated storage layer in the hydrology of tile drains in loam soils. Novel aspects of this module include the sub-daily time step, which is shorter than most existing models, and the use of field capacity and its corresponding pressure head to provide estimates of drainable water and the thickness of the capillary fringe, rather than using detailed soil retention curves that may not always be available. An additional novel aspect is the demonstration that flows in some tile drain systems can be better represented and simulated when related to shallow saturated storage dynamics.

Footprints on the beach: visualizing dilation-induced air entry

The dry fringe that appears beneath a footprint on a beach is a visual manifestation of dilation. Dilation causes the sand to attempt to increase in volume on shearing, resulting in negative pore pressure, and enhanced bearing capacity. Conventional theory cannot explain this increase in strength, suggesting instead that bearing capacity with the phreatic surface at the sand surface should be approximately half that of the dry case. To explore this apparent contradiction, ten load-controlled bearing capacity experiments were performed on transparent soil with phreatic surfaces ranging from 100 mm below to 30 mm above the footing. For phreatic surfaces deeper than the footing width, failure occurred within the dry material. In shallower phreatic surface conditions, bearing capacity increased as the phreatic surface approached the surface. Air entry was observed to initiate along the top surface of the saturated layer and extend to the depth of the bearing capacity mechanism. For the case of the phreatic and soil surfaces being coincident, the bearing capacity was observed to be more than double that of the dry case. In submerged cases bearing capacity was less than at-surface, as there was no air-fluid interface to enhance the development of negative pore pressure.

Dynamic modeling of minimum mass of pore-gas for triggering landslide in stable gentle soil slope

This paper presents a dynamic modeling method to test and examine the minimum mass of pressurized pore-gas for triggering landslides in stable gentle soil slopes. A stable gentle soil slope model is constructed with a dry cement powder core, a saturated clay middle layer, and a dry sand upper layer. The test injects H2O2 solution into the cement core to produce new pore-gas. The model test includes three identical H2O2 injections. The small mass of generated oxygen gas (0.07% of slope soil mass and landslide body) from the first injection can build sufficient pore-gas pressure to cause soil upheaval and slide. Meanwhile, despite the first injection causing leak paths in the clay layer, the generated small mass of gas from the second and third injections can further trigger the landslide. A dynamic theoretical analysis of the slope failure is carried out and the required minimum pore-gas pressure for the landslide is calculated. The mass and pressure of generated gas in the model test are also estimated based on the calibration test for oxygen generation from H2O2 solution in cement powder. The results indicate that the minimum mass of the generated gas for triggering the landslide is 2 ppm to 0.07% of the landslide body. Furthermore, the small mass of gas can provide sufficient pressure to cause soil upheaval and soil sliding in dynamic analysis.

Determination of the geophysical signature of soft-clay and hard lateritic soils and the implications on geotechnical works using electrical resistivity imaging

Understanding the geophysical signature of subsurface is quite essential in mapping site conditions for geotechnical engineering and simulating geophysical surveys, especially in coastal areas. This article presents a comparative geophysical study of topsoil (often refer as engineering layer) of soft clay deposit and hard lateritic soil to evaluate the implications on geotechnical work using electrical resistivity imaging (ERI). The results of the 2D ERI show that the hard lateritic soil produces three distinctive geological layers with the topsoil having high apparent electrical resistivity (AER) values varying between 300 Ωm–1000 Ωm and a thickness between 2.0 m – 10.0 m. The layer between the unsaturated and saturated regions has a moderate layer AER and thickness values ranging from 100 Ωm–300 Ωm and 2.5 m–9.5 m, respectively. In contrast, the saturated (weathered) layer has a low AER value (< 100Ω m), which represents the regional groundwater unit, located beneath the subsurface of a depth > 6.0 m. However, the soft clay soil shows no distinctive subsurface layers, as it is characterized by a nearly homogeneity subsurface of poor AER variability. The top-soft clay deposit has very AER values ranging from 11.0 Ωm–80 Ωm, which extends beyond 6.5 m. Higher and lower AER values noted within the overburdened topsoil of lateritic and clay extractions, respectively, were due to the accumulations of compacted clay and lateritic soil, which are very essential for geotechnical works. In addition, the geophysical signal was conspicuously attenuated in soft clay soil, which shows that soft clay soil is not a favourite target of geophysical investigation. However, the geophysical signals in hard lateritic generate a fine geo-electrical layer pattern. It was also noted that the existence of soft clay and lateritic soil decreases with depth. This kind of information is very essential in geotechnical works.

Monitoring moisture dynamics in multi-layer cover systems for mine tailings reclamation using autonomous and remote time-lapse electrical resistivity tomography

The dynamics of moisture content in cover systems constructed on mining wastes were monitored at the pilot scale using 2D autonomous, remote, and non-invasive time-lapse electrical resistivity tomography combined with conventional point sensors. A methodology was proposed to process the daily hydrogeophysical datasets from 23 m-long instrumented sections of covers with capillary barrier effects (CCBEs) designed to act as oxygen barriers, and covers with low saturated hydraulic conductivity layers (LSHCCs) designed to limit the water infiltration rate. Hydrogeophysical monitoring suggested that CCBEs were able to maintain high degrees of saturation in the moisture-retaining layer throughout the one-year monitoring period, which would make it an efficient oxygen barrier. Larger spatio-temporal changes in moisture content were observed in LSHCCs and most of the low hydraulic conductivity layers remained below 85% saturation, which was attributed to the combined effect of low precipitation, rapid vegetation development, and water percolation through the cover. The methodology proposed in this pilot-scale "proof-of-concept" study allowed the hydrogeological behavior of the cover systems to be monitored in the 23 m-long instrumented sections using continuous geoelectrical data, which demonstrated that this innovative monitoring technique could be useful for geochemical and geotechnical monitoring programs in large-scale mining waste storage facilities.

The formation mechanism of low-angle loess-mudstone seismic landslides

Seismic-induced landslides represent intricate geological phenomena requiring a multidisciplinary investigative approach. This study examines the formation mechanisms of low-angle loess-mudstone landslides triggered by the 1920 Haiyuan M8.5 earthquake. We employ a synthesis of field investigations, high-density electrical resistivity tests, drilling, laboratory experiments, and numerical simulations. High-density resistivity results support the identified zone at the loess-mudstone interface, indicating a saturated area prone to liquefaction. Dynamic triaxial tests further verify liquefaction occurrences during seismic events within this zone. Additionally, numerical simulations conducted with FLAC2D and the PM4Silt constitutive model provide valuable insights into the temporal and spatial progression of landslides. The liquefaction zone experiences severe shear strain, precisely aligning with the location of the sliding band. Shear strain time-history analyses elucidate early manifestations and time-dependent behaviors at interfaces, providing a nuanced understanding of deformation patterns. The study delineates a comprehensive failure mechanism, unraveling how liquefaction in the saturated loess layer initiates in the upper and toe regions, subsequently propagating throughout the slope. Tension in the upper part and compressive uplift at the toe manifest, resulting in overall landslide movement. These findings highlight the significance of differential shear strain, leading to a layered shear deformation zone. The results yield invaluable insights for seismic stability assessments in regions with similar geological characteristics. This research not only advances the understanding of earthquake-induced landslides but also demonstrates the synergy between field investigations, advanced geotechnical testing, and numerical modeling in unraveling complex geological processes.