Water Infiltration Research Articles

Sustainability Nexus AID: soil health

The Sustainability Nexus Analytics, Informatics, and Data (AID) Programme of the United Nations University (UNU), aims to provide information, data, computational, and analytical tools to support the sustainable management and long-term security of natural resources using a nexus approach. This paper introduces the Soil Health Module of the Sustainability Nexus AID Programme. Healthy soil is crucial for life on Earth, and it is essential for ecosystem services and functioning, access to clean water, socioeconomic structure, biodiversity, and food security for the growing population of the world. Healthy soils contribute to mitigating the effects of climate change and reduce the consequences of extreme events such as flooding and drought. Healthy soils influence the hydrologic cycle by regulating transpiration, water infiltration, and soil water evaporation affecting land–atmosphere interactions. The Soil Health Module of the UNU Sustainability Nexus AID Programme aims to evolve into the ultimate focal point, supporting a diverse array of stakeholders with state-of-the-art data and tools that are essential for soil health monitoring and projection. This paper discusses the importance of adopting a nexus approach for ensuring soil health, explores the AID tools currently at our disposal for quantifying and predicting soil health, and concludes with recommendations for future effort and direction within the Sustainability Nexus AID Programme concerning soil health.

Effects of soil bulk density and corresponding soil infiltration rate on the migration and transformation of gibberellic acid.

High intensity agricultural activities can lead to a decrease in soil fertility and an increase in soil bulk density, which may significantly impact the migration and transformation of pesticides in soil. As a new widely-used micro-toxic pesticide, gibberellic acid (GA3) is more soluble and hydrophilic than most pesticides, which could readily migrate throughout the soil during water infiltration and impact groundwater quality. In this study, the leaching of GA3 in saturated soils with different bulk densities (1.15-1.75g/cm3) and infiltration rates (0.2215-0.0017mm/s) were analyzed using column experiments. The migration and distribution of GA3 in the soil with a depth of 50cm were also investigated. The results indicated that GA3 could completely penetrate the soil with bulk densities less than 1.45g/cm3, and GA3 mass variation in the effluent was normally distributed. The maximum mass of GA3 in the effluent was calculated using the equation Moutlet(max)=79.01t-0.97 (R2=0.9811), and 83.69-93.16% mass of the added GA3 migrated downward in the soil. The analysis of the distribution of GA3 in the soil showed that GA3 accumulated in the upper soil layers with depths of 0-25cm (the total depth of soil was 50cm). In addition, the residual and hydrolyzed GA3 amounts in the soil were 75.07-96.47% and 5-30% of the added GA3, respectively. Overall, the soil bulk density and irrigation volume determine what type of impact that GA3 may potentially have on the environment.

Effect of shrubland-to-grassland conversion on soil water storage and infiltration capacity in Loess Plateau region of China

Effect of shrubland-to-grassland conversion on soil water storage and infiltration capacity in Loess Plateau region of China

Water Infiltration from Flash Floods, and its Disappearance into Alluvial Sediments in Semi-arid Regions

Water Infiltration from Flash Floods, and its Disappearance into Alluvial Sediments in Semi-arid Regions

Pressurised water flow in fractured permafrost rocks revealed by borehole temperature, electrical resistivity tomography, and piezometric pressure

Abstract. Rock slope instabilities and failures from permafrost rocks are among the most significant alpine hazards in a changing climate and represent considerable threats to high-alpine infrastructure. While permafrost degradation is commonly attributed to rising air temperature and slow thermal heat propagation in rocks, the profound impact of water flow in bedrock permafrost on warming processes is increasingly recognised. However, quantifying the role of water flow remains challenging, primarily due to the complexities associated with direct observation and the transient nature of water dynamics in rock slope systems. To overcome the lack of a quantitative assessment, we combine datasets of rock temperature measured in two deep boreholes (2016–2023), with electrical resistivity tomography measurements repeated monthly in 2013 and 2023; the site-specific temperature–resistivity relation determined in the laboratory with samples from the study area; and borehole piezometer data. Field measurements were carried out at the permafrost-affected north flank of the Kitzsteinhorn (Hohe Tauern range, Austria), which is characterised by significant water outflow from open fractures during the melt season. Borehole temperature data demonstrate a seasonal maximum of the permafrost active layer of 4–5 m. They further show abrupt temperature changes (∼ 0.2–0.7 °C) at 2, 3, and 5 m depth during periods with enhanced water flow and temperature regime changes between 2016–2019 and 2020–2022 at 10 and 15 m depth, which cannot be explained solely by conductive heat transfer. Electrical resistivity measurements repeated monthly reveal a massive decrease in resistivity from June to July and the initiation of a low-resistivity (< 4 kΩ m) zone in the lower part of the rock slope in June, gradually expanding to higher rock slope sections until September. We hypothesise that the reduction in electrical resistivity of more than an order of magnitude, which coincides with abrupt changes in borehole temperature and periods of high water heads up to 11.8 m, provides certain evidence of snowmelt water infiltration into the rockwall becoming pressurised within a widespread fracture network during the thawing season. This study shows that, in addition to slow thermal heat conduction, permafrost rocks are subjected to sudden push-like warming events and long-lasting rock temperature regime changes, favouring accelerated bottom-up permafrost degradation and contributing to the build-up of hydrostatic pressure, potentially leading to slope instability.

Computer simulation of the soil water regime under an apple orchard in a mountainous area (using the example of the leached chernozem of the experimental agricultural station Gorno-Altaiskoe)

Relevance. Progressive degradation of farmland soils – erosion, salinization, desertification. Aim. To establish features of water-physical properties of leached chernozem under an apple orchard and associated patterns of soil profile moisture distribution in summer period when precipitation deficiency observed. Methods. Moisture content in soil horizons was determined by the gravimetric method. To determine the granulometric composition of soils, the pipette method was used. The soil bulk density was determined by the cutting ring method. For solid phase density determination the pycnometric method was used. The method of graphic interpolation was used for transition the soil texture classification from Russian to international one. Water infiltration modeling into the soil profile was carried out using the HYDRUS-1D program. The parameters of approximating of the water retention curve of soils by the Van Genuchten equation were obtained by the calculation method of pedotransfer functions «Rosetta Lite» of the RETC program, using data on soil density and soil texture. Results. It has been established that the upper well-structured horizons of leached chernozem under an apple orchard have a greater water-holding capacity; their water-retention curves are more flattened. The water retention curve of the more structureless B2k horizon, the soil texture of which is dominated by sandy fractions, is shifted towards lower humidity. During hot and dry summer period the moisture deficiency in the soil was noted only in the upper twenty-centimeter soil column (14 mm). The moisture of the lower horizons, where the bulk of tree roots are concentrated, is satisfactory. The model demonstrates the smallest discrepancies with the moisture values measured during the soil reclamation experiment one day after the start. The downward moisture penetration into the lower soil layers is prevented by low pressure in the clayey A and AB horizons. Selection of input parameters and debugging of the model based on experimental data allows it to be used to simulate further processes occurring in the soil. It was revealed that the formation of positive (upward) water flows, which ensure the “pull-up” of salts and substances from the lower part of the profile to the upper layers during dry periods of the year, has a significant impact on moisture distribution in the chernozem under the apple orchard.

Utilizing hydrophobic sand to construct an air permeable aquiclude to enhance rice yields

The Chinese government attaches great importance to the ecological restoration of abandoned open-pit mines, increasing the area of cultivated land, and ensuring food security. Soil reconstruction is a crucial step in ecological restoration of abandoned open-pit mines. This study investigated the utilization of hydrophobic sand to create an Air-Permeable Aquiclude (APAC) under the plant root zones, thereby minimizing water infiltration and enhancing soil aeration. Field plot experiments for 2 years have been conducted, with control groups, Clay Aquitard (CAT), and Plastic Aquiclude (PAC), to evaluate the effects of APAC on rice yield, nitrogen utilization, and water efficiency. The findings revealed that utilizing APAC resulted in a significant rise in rice yield, ranging from 8.09 t/hm² to 9.27 t/hm², which were 7.67–27.16% higher than the control groups. Moreover, the APAC led to a remarkable reduction in irrigation water usage by 37.08%, alongside a substantial boost in Irrigation Water Productivity (IWP) efficiency by 28.64–71.12%. Notably, Nitrogen Partial Factor Productivity (NPFP) exhibited a substantial increase of 7.69–27.06%. These outcomes underscore the APAC’s positive role in water and nutrient conservation and enhanced yields.

X-ray tomography offers detailed look at early stage of espresso brewing

High-speed rotating X-ray system leads to clearer understanding of water infiltration of the coffee grounds.

Characterizing and Modeling Infiltration and Evaporation Processes in the Shallow Loess Layer: Insight from Field Monitoring Results of a Large Undisturbed Soil Column

Frequent agricultural irrigation events continuously raise the groundwater table on loess platforms, triggering numerous loess landslides and significantly contributing to soil erosion in the Chinese Loess Plateau. The movement of irrigation water within the surficial loess layer is crucial for comprehending the mechanisms of moisture penetration into thick layers. To investigate the infiltration and evaporation processes of irrigation water, a large undisturbed soil column with a 60 cm inner diameter and 100 cm height was extracted from the surficial loess layer. An irrigation simulation event was executed on the undisturbed soil column and the ponding infiltration and subsequent evaporation processes were systematically monitored. A ruler placed above the soil column recorded the ponding height during irrigation. Moisture probes and tensiometers were installed at five depths to monitor the temporal variations in volumetric water content (VWC) and matric suction. Additionally, an evaporation gauge and an automatic weighing balance measured the potential and actual evaporation. The results revealed that the initially high infiltration rate rapidly decreased to a stable value slightly below the saturated hydraulic conductivity (Ks). A fitted Mezencev model successfully replicated the ponding infiltration process with a high correlation coefficient of 0.995. The monitored VWC of the surficial 15 cm-thick loess approached a saturated state upon the advancing of the wetting front, while the matric suction sharply decreased from an initial high value of 65 kPa to nearly 0 kPa. The monitored evaporation process of the soil column was divided into an initial constant rate stage and a subsequent decreasing rate stage. During the constant rate stage, the actual evaporation closely matched or slightly exceeded the potential evaporation rate. In the decreasing rate stage, the actual evaporation rate fell below the potential evaporation rate. The critical VWC ranged from 26% to 28%, with the corresponding matric suction recovering to approximately 25 kPa as the evaporation process transitioned between stages. The complete evaporation process was effectively modeled using a fitted Rose model with a high correlation coefficient (R2 = 0.971). These findings provide valuable insights into predicting water infiltration and evaporation capacities in loess layers, thereby enhancing the understanding of water movement within thick loess deposits and the processes driving soil erosion.

Characterization and identification of elemental sulphur, iron pyrite, mineral gypsum, phospho gypsum and marine gypsum using SEM-EDAX

India has 6.73 million ha of salt-affected soils, of which 3.77 million ha is sodic soil. Sodicity is a serious issue in agriculture, and it prevents to meet the properties of fertile soil. Sodicity alters its physical and chemical properties, including soil structure and hydraulic conductivity. High exchangeable sodium and pH decrease soil permeability, available water capacity and infiltration rates through swelling and dispersion of clays as well as slaking of soil aggregates. Gypsum is one of the sources used for sodic soil reclamation, and the cheaper and alternative source is marine gypsum which is recovered from salt pans during production of common salt in coastal region, particularly in Gujarat and Tamil Nadu. The recovery of by-product gypsum and marine gypsum together is substantial and is comparable with the production of mineral gypsum.The amendments generally used for sodic soil reclamation should be a source of sulphates such as elemental sulphur, iron pyrite, mineral gypsum, phospho gypsum and marine gypsum. Characterization of sources by SEM–EDAX is rapid and elementary. The elemental composition revealed by the spectra of the bentonite sulphur for weight percentage and atomic percentage of sulphur is quantified as 34.04% and 18.59%, respectively, in the ZAF matrix. In iron pyrite spectra the weight percentage and atomic percentage of sulphur are 4.89% and 2.31%,respectively, in the ZAF matrix, while in mineral gypsum, the calcium weight percentage is 10.14% and atomic percentage is 04.04% while sulphur weight percentage is 6.52%, atomic percentage is 3.50%. The calcium composition in phosphogypsum is weight percentage is 14.69%; Atomic percentage is 34%, and the sulphur composition in phosphogypsum is weight percentage 10.40%, atomic percentage 5.60%, whereas in marine gypsum the calcium (weight percentage 09.10%, atomic percentage 03.58%) and sulphur (weight percentage 06.28%, atomic percentage 03.09%) proportions dominate as like two other above-mentioned gypsums, the element which makes difference in the marine gypsum from others is sodium (Weight percentage 00.18%, atomic percentage 00.12%). This helps to confirm that marine gypsum is an economic and alternate source available for sodic soil reclamation.

Analisis Tingkat Erosi Menggunakan Metode USLE di Kapanewon Panggang Kabupaten Gunungkidul Daerah Istimewa Yogyakarta

One of the causes of critical land is erosion; the greater the intensity of erosion, the more critical the land becomes. The distribution of erosion predictions is influenced by variables such as rainfall erosivity, soil erodibility, slope length and steepness, ground cover vegetation, land use, and land conservation. One of the critical lands is located in Kapanewon Panggang, Gunungkidul Regency, Special Region of Yogyakarta, covering an area of 9130.01 hectares, which consists of six villages: Giriharjo, Girisuko, Giriwungu, Girimulyo, Girikarto, and Girisekar. The purpose of this study is to determine the erosion rate in Kapanewon Panggang, to assess the level of erosion hazard in Kapanewon Panggang, and to formulate a land management concept based on actual land use conditions with erosion criticality parameters in Kapanewon Panggang, Gunungkidul Regency, Special Region of Yogyakarta. The method used is the USLE (Universal Soil Loss Equation). USLE is an erosion model designed to predict long-term erosion from sheet or rill erosion under specific conditions. USLE is used on both agricultural and non-agricultural lands. The results show that the erosion hazard levels in Kapanewon Panggang are categorized as very light (1184.28 hectares), light (1074.65 hectares), moderate (1831.70 hectares), severe (2411.01 hectares), and very severe (2628.38 hectares). The factors that most influence the magnitude of erosion are land use, slope length, and steepness. The land management concept to minimize erosion can be implemented based on land cover, namely in residential areas where water infiltration areas are needed, in savanna land use where additional vegetation and ground cover plants are necessary, and based on slope length and steepness, mechanical conservation by constructing bench terraces and stone bunds should be applied.

Determining the Role of Urban Greenery in Soil Hydrology: A Bibliometric Analysis of Nature-Based Solutions in Urban Ecosystem

Nature-based solutions play an essential role in enhancing urban soil hydrology by improving water retention properties, reducing surface runoff, and improving water infiltration. This bibliometric analysis study reviewed the literature and identified the current trends in research related to nature-based solutions in urban soil hydrology. The study has the potential to highlight current research areas and future hot topics in this specific field. The research used the Scopus database to collect published articles from 1973 to 2023. The keywords (“trees” OR “vegetation” OR “green infrastructure” OR “blue green infrastructure” OR “greenery” OR “nature-based solutions” AND “hydrolog*” AND “urban” OR “city” OR “soil”) were searched in the Scopus database, and 13,276 articles were retrieved. The obtained publications were analyzed for bibliometric analysis by using Bibliometrix (v4.3.0) and VOSviewer (v1.6.20) software. The maximum number of publications (970) related to nature-based solutions and urban soil hydrology was published in 2023. Additionally, countries such as the United States and China published 54.2% of articles of the global research in the field of nature-based solutions and urban soil hydrology, with 36% from the USA and 18.2% of articles from China. The bibliometric analysis depicted that Beijing Normal University led this specific research field with 540 articles. The top country in terms of collaboration was the USA, with 26.17% as compared to the global countries. The most productive researcher identified was Jackson, T.J., as he had the highest number of publications, showing his considerable contribution to the field. Furthermore, the most frequent keywords used in this research area were hydrology, ecosystem services, urban hydrology, remote sensing, nature-based solutions, climate change, runoff, stormwater management, water quality, vegetation, green roof, bioretention, and land use. The early research trending topics in this field from 2015 to 2023 were remote sensing, soil moisture, climate change, drought, green infrastructure, machine learning, and nature-based solutions. The bibliometric analysis identified limited interdisciplinary research integrations, not using well-significant and standardized methodologies for the evaluation of urban soil hydrology, and under-representation of research from developing countries as current research gaps. Future research directions highlight advanced methods such as combining data-driven technologies with traditional hydrological approaches, and increasing international collaboration, specifically in developing nations, to address urban soil hydrological problems properly.

Using roof borehole electrical resistivity tomography to monitor roof water infiltration in a mine work face

Roof water inrush in coal mining is a significant type of water-related disaster that usually results from the interconnection of water-bearing geological formations formed by cracks during and after work face mining. Therefore, monitoring roof water infiltration is of paramount importance in preventing or mitigating water inrush in the mine work face. This study employed the roof borehole electrical resistivity tomography method to conduct physical experiments for monitoring water seepage in roof cracks generated during coal model mining. Additionally, roof water infiltration monitoring was performed in the 7130 work face of the Qidong Coal Mine. The results of both physical experiments and field tests demonstrate that roof borehole electrical resistivity tomography (ERT) is well suited for monitoring roof water infiltration in mine work faces, enabling the determination of the temporal and spatial distributions of water seepage. By analyzing the variation patterns of low-resistivity anomalies in the resistivity profile, the water-conducting channels and water outflow points can be identified. Experiments and field tests suggest that the resistivity and its changes are related to the amount of water inflow and water channel. With the increase of water inflow, the relatively low resistivity anomalies region increases, the resistivity value decreases and the water channel appears and expands. With the amount of water inflow decreasing, the relatively low resistivity area becomes smaller, the resistivity value increases, and the water channel narrows or even disappears.Furthermore, by combining the areas of low-resistivity anomalies, a qualitative assessment of the water content can be achieved. Finally, The results of the periodic weighting analysis of the field tests indicate that roof water infiltration is related to periodic weighting. The greater the periodic weighting is, the more severe the roof water infiltration.

Water pervious concrete pavement blocks: durable structures for an integrated water policy

Water pervious pavement blocks are a durable and ecological solution to prevent water run off, to minimize the risk of flooding and to increase the efficiency of water purification. The application of water pervious pavement blocks on a permeable base and/or sub base allows buffering of the rainwater in the structure and infiltration or retarded outflow to the ground or infiltration system. This paper presents the results of a research project, conducted at the BRRC during 4 years. The efficiency of water buffering and infiltration in relation to the choice of material is investigated in the laboratory, on a test parking lot and on site. To allow a good choice of the materials and the application site and to control the efficiency on site, different test methods are optimized. Results for different types of concrete pavement blocks (pervious blocks, blocks with enlarged joints or drainage holes), different types of base layer (hydraulic bounded or unbounded materials) and different types of sand layer and jointing materials are looked at. Finally this paper focuses on several applications in Belgium, where measurements have shown a good behavior of the structure and a good durability of the permeability. Data from newly constructed projects, as well as projects in use for more than eight years are presented.

Effect of collapse-type lateral pressure induced by irrigation on loess landslides

Loess collapse-type lateral pressure may have a landslide-promoting effect in loess slope areas. A study on the variability of loess collapse-type lateral pressure in the Heifangtai area and its sliding mechanism has been analysed. Collapse tests and numerical simulations were conducted according to local safety field theory. The results indicate that the Heifangtai loess is self-weighted collapsible loess. As the depth or moisture content increases, the lateral pressure gradually increases, and correspondingly the deformation becomes greater. In a saturated state, the maximum lateral pressure reaches 123 kPa, and the lateral pressure coefficient increases up to 1.4 times. As the water content increases from 4% to 20%, the total slope displacement is predominantly horizontal, increasing from 12 to 140 mm, the lateral pressure coefficient gradually increases and the increase range gradually expands; the failure area becomes gradually wider until the slope toe is penetrated. Collapse action leads to tensile stresses in the upper part of the slope, making it prone to collapse-type crack formation, resulting in dominant channels of surface water infiltration and forming landslide scarps. Furthermore, collapse action also enables the formation of compressive stresses in the lower part of the slope, resulting in outward extrusion of deep soil, increased sliding force and landslide formation.

Time-lapse shear-wave tomography at a test dyke with changing water levels

Although seismic methods using S waves can offer high-resolution images of the shallow soil layers, the use of body S-wave tomography for near-surface water monitoring remains underexplored, and the quantitative interpretation of any observed changes in S-wave velocity ( V S) in the field conditions is challenging. We conduct a time-lapse S-wave tomography experiment on a field-scale test dike with controlled water levels, allowing for detailed examination of how VS responds to water infiltration. Our results demonstrate that VS decreases progressively, starting from the high-water-side slope and extending across the dike, as the water level rises, with the most significant changes occurring in the sand body and not in the clay cover. The maximum reduction in VS is approximately 40–60 m/s, corresponding to approximately 25%–30% reduction from the initial condition. We use the squared velocity ratio to evaluate the relative contributions of bulk density and shear modulus to VS changes. In the initially unsaturated zone, both these factors contribute significantly to the observed VS changes as the zone becomes fully saturated. In fully saturated zones, we assess the changes in the effective stress using the squared VS ratio. Although the low-water side of the dike shows stress changes that are consistent with numerical modeling, the high-water side shows large stress changes than expected, possibly due to excess pore pressure during the dynamic flow conditions. These findings highlight the potential of body S-wave tomography for high-resolution, near-surface hydrologic monitoring, and provide insights into the complex interactions between physical properties that influence VS changes under varying water levels in field environments.

Modified Green-Ampt model for infiltration analysis in loess area and its parameter determination and verification

Water infiltration into soil is important in geotechnical engineering. The classical Green-Ampt (GA) infiltration model is widely used in soil infiltration due to its physical significance, but it ignores the actual unsaturated layer in the infiltration process and has some deficiencies. Thus, the present study established a modified GA infiltration model (MLGA model) using Darcy’s infiltration law and continuity equation to fully consider the variation characteristics of the soil water profile in the infiltration process. The Philip model and the GA model have the same physical basis. By combining the internal relationship between the infiltration rate and cumulative infiltration of the two models, the expression of matrix suction of the MLGA model was obtained. The existing measured data was used to verify the correctness and applicability of the MLGA model. Finally, the sensitivity analysis of the critical parameters of the model was performed. The results showed that the MLGA model is reliable and can be used for water infiltration analysis in loess sites. When the MLGA model is used to calculate the infiltration depth, the maximum relative error between the calculated value and the measured data is less than 10%, and the average relative error is 5.54%, which indicates that the model has a high calculation accuracy. The average error of the MLGA model is 24.47% of the Kostiakov model and 80.42% of the existing modified GA model (LGAM model). Sensitivity analysis of the saturated permeability coefficient, initial water content, saturated water content, and matrix suction was performed using the single-factor disturbance method. The influence of each parameter on infiltration depth was summarized, and the sensitivity of each parameter was quantitatively evaluated, which revealed that saturated water content is a highly sensitive parameter. When using the MLGA model to calculate infiltration depth, the accuracy of saturated water content should be ensured first. Finally, the difference between the MLGA model and the LGAM model in describing the whole process of water infiltration is discussed, and the influence mechanism of critical parameters on the water infiltration process is deeply analyzed. The established MLGA model provides theoretical support for further study of the loess water infiltration mechanism.

Active volume of water in a laboratory aquifer

During a rainfall event, water infiltrates into the ground where it accumulates in porous rocks. This accumulation pushes the underlying groundwater towards neighbouring streams, where it runs to the sea. After the rain has stopped, the aquifer gradually releases its excess water, as the water table relaxes, until the next rain. In the absence of recharge, the water table would eventually reach its horizontal equilibrium position. The volume of groundwater stored above this level, which we call the active volume, sustains the river between two rainfall events. In this article, we use an experimental aquifer recharged by artificial rain to investigate how this active volume depends on the rainfall rate. Restricting our analysis to the steady-state regime, wherein the discharge into the stream balances rainfall, we explore a broad range of rainfall rates, for which the water table deforms significantly. We find that the active volume of water stored in the aquifer decreases with its depth. Using conformal mapping, we derive the flow equations and develop a numerical procedure that accounts for the active volume of groundwater in our experiments. In the case of an infinitely deep aquifer, the problem admits a closed-form solution, which provides a satisfying estimate of the active volume when the aquifer's depth is at least half its width. In the general case, a rougher estimate results from the energy balance of the dissipative groundwater flow.

Hydroxyl Radical-π Interaction in a Single Crystal.

Numerous attempts for organic radical stability mostly entail steric hindrance, spin-delocalization, supramolecular interaction with the host, π-π interactions, and hydrogen bonding. To date, there is no report of single crystals containing a hydroxyl radical (•OH). In this work, we have stabilized •OH in the crystal, which has been obtained from the filtrate after separating the precipitate of the chromenopyridine radical (DCP(2)•) from the reaction mixture. DCP(2)• abstracts a hydrogen atom from dissolved water in the ethanolic filtrate to grow the single crystal containing DCPH(2) and •OH in the asymmetric unit. The crystal packing and computational studies suggest that π-•OH and •OH···N hydrogen-bonding interactions are responsible for stabilizing •OH. The presence of •OH has been further confirmed by mass analysis with the 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) adduct. Solid-state electron paramagnetic resonance (EPR), solution state nitroblue tetrazolium (NBT) assay, and spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in the presence of super oxide dismutase suggest •OH formation in the single crystal.

Study on mechanical properties and strength criterion of mudstone under loading and unloading considering pre-peak damage

In the highway construction of the southwestern Transverse Mountain area of China, mass mudstone engineering disasters have occurred, primarily attributed to engineering disturbances and water-rock interaction. Engineering disturbances commonly lead to varying degrees of pre-peak damage. To elucidate the evolutionary laws of strength in pre-peak damaged mudstone, we first defined the pre-peak damage variable ( Da) for mudstone, and through triaxial loading and unloading tests, obtained the mechanical characteristics of pre-peak damaged mudstone, analyzing its brittle properties from an energy perspective. Subsequently, through scanning electron microscopy tests, we analyzed the microstructural features to reveal the failure mechanism. Finally, the damage ratio strength theory (DR) was introduced to characterize the strength of the mudstone and validate the suitability of the DR. The results demonstrate that: (1) Mudstone with pre-peak damage exhibits a significant weakening effect due to water-rock interaction, with a maximum reduction in peak strength of approximately 28%. Compared to the loading stress path (LSP), the overall strength of the mudstone is lower under the unloading stress path (ULSP), and the deformation modulus decreases more significantly with Da under the ULSP. (2) Both the Daand confining pressure contribute to a decrease in the brittleness index of the mudstone. Under the ULSP, the mudstone is more prone to brittle failure. (3) The development of micro-cracks in pre-peak damaged mudstone makes it more susceptible to water infiltration, exacerbating the deteriorating effect of water-rock interaction, thus affecting its mechanical properties. (4) The DR can effectively characterize the strength of pre-peak damaged mudstone. The Damage Ratio (ν D,c) of mudstone under the LSP is in the range of 1.07∼1.50, and under the ULSP is in the range of 1.11∼1.52. The ν D,c under the LSP is smaller than under the ULSP, decreases with the Da, and exhibits plastic deformation, indicating that the DR can simultaneously characterize the strength and brittleness of the mudstone. The research results can provide guidance for the design parameters and disaster prevention of disturbed mudstone engineering.