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Bisphenol AF (BPAF) and TGSA are analogues of Bisphenol A (BPA). BPAF is used in polymer synthesis, while TGSA is applied in thermal papers. The EU classifies BPAF as toxic to reproduction and TGSA as a skin sensitizer. However, TGSA's other health effects remain unclear. BPAF contamination has been noted among electronic waste workers, and TGSA exposure is documented in various professions. Despite the significance of skin contact, data on skin permeation rates for BPAF and TGSA are limited. This study aimed to generate percutaneous absorption data for BPAF and TGSA following OECD guidelines. [14C]-labelled BPAF or TGSA was applied to human skin samples in vitro using Franz diffusion cells for 20 and 40 h, respectively. Key parameters such as steady-state flux, lag time, and skin permeability coefficient (Kp) were calculated. Furthermore, the distribution of the dose across different compartments, particularly within the skin, was evaluated at the conclusion of the experiment. Sequential strippings and epidermis-dermis separation were conducted for BPAF to predict the potential absorption of the remaining dose present within the skin. The permeability coefficients for BPAF and TGSA were found to be 1.9 E-03 and 1.6 E-03 cm/h, with 22% and 23% of the applied doses absorbed, respectively. Both chemicals are classified as "fast" penetrants based on their Kp values. These findings suggest that BPAF and TGSA are absorbed through the skin, highlighting potential occupational risks through dermal exposure. The new percutaneous absorption data will enhance the assessment of the occupational risks.
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The internal pore structural characteristics and microbubble distribution features of concrete have a significant impact on its frost resistance, but their size is relatively small compared to aggregates, making them difficult to visually represent in the mesoscopic numerical model of concrete. Therefore, based on the ice-crystal phase transition mechanism of pore water and the theory of fine-scale inclusions, this paper establishes an estimation model for effective thermal conductivity and permeability coefficients that can reflect the distribution characteristics of the internal pore size and the content of microbubbles in porous media and explores the evolution mechanism of effective thermal conductivity and permeability coefficients during the freezing process. The segmented Gaussian integration method is adopted for the calculation of integrals involving pore size distribution curves. In addition, based on the concept that the fracture phase represents continuous damage, a switching model for the permeability coefficient is proposed to address the fundamental impact of frost cracking on permeability. Finally, the proposed estimation models for thermal conductivity and permeability are applied to the cement mortar and the interface transition zone (ITZ), and a thermal-hydraulic-mechanical coupling finite element model of concrete specimens at the mesoscale based on the fracture phase-field method is established. After that, the frost-cracking mechanism in ordinary concrete samples during the freezing process is explored, as well as the mechanism of microbubbles in relieving pore pressure and the adverse effect of accelerated cooling on frost cracking. The results show that the cracks first occurred near the aggregate on the concrete sample surface and then extended inward along the interface transition zone, which is consistent with the frost-cracking scenario of concrete structures in cold regions.
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Corneal blindness can be treated by keratoplasty but a lack of readily available corneal donor tissue for this procedure remains a challenge. Cryopreservation can facilitate the long-term storage of tissue but effective protocols for cryopreserving cornea have yet to be developed. Mathematical modelling can guide protocol design, but previously used models are not comprehensive. A comprehensive model should describe the tissue's shrink-swell response and the cryoprotectant concentration throughout the tissue during cryoprotectant loading. Such a model exists for articular cartilage based on a biomechanical triphasic approach. We explored the applicability of this model for describing cryoprotectant permeation in porcine corneas by fitting it to experimental data for the permeation of dimethyl sulfoxide into porcine corneoscleral discs. The model provided as good of a fit for corneoscleral discs data as it did for articular cartilage data, presenting promise for its use in the design of cryopreservation protocols for corneas.
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Total ammoniacal nitrogen (TAN) occurs in various wastewaters and its recovery is vital for environmental reasons. Forward osmosis (FO), an energy-efficient technology, extracts water from a feed solution (FS) and into a draw solution (DS). Asymmetric FO membranes consist of an active layer and a support layer, leading to internal concentration polarization (ICP). In this study, we assessed TAN recovery using a polymeric thin-film composite FO membrane by determining the permeability coefficients of NH4+ and NH3. Calculations employed the solution-diffusion model, Nernst-Planck equation, and film theory, applying the acid-base equilibrium for bulk concentration corrections. Initially, model parameters were estimated using sodium salt solutions as the DS and deionized water as the FS. The NH4+ permeability coefficient was 0.45 µm/s for NH4Cl and 0.013 µm/s for (NH4)2SO4 at pH < 7. Meanwhile, the NH3 permeability coefficient was 6.18 µm/s at pH > 9 for both ammonium salts. Polymeric FO membranes can simultaneously recover ammonia and water, achieving 15% and 35% recovery at pH 11.5, respectively.
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In order to meet the needs of low-impact development and sustainable development, there is an urgent desire to develop an innovative recycled aggregate pervious concrete (I-RAPC) that is of high strength and permeability. In this study, I-RAPC was prepared based on response surface methodology (RSM) using recycled aggregate, river sand, and different types of pipes as the materials, and the effects of different pipe parameters (number, diameter, material, and distribution form) on the performance of I-RAPC were investigated. In addition, the calculation model of the compressive strength and the permeability coefficient of I-RAPC were proposed. The results showed that the frontal- and lateral-compressive strengths of I-RAPC were 39.8 MPa and 42.5 MPa, respectively, when the pipe material was acrylic, the position was 1EM, and the diameter was 10 mm-at which time the permeability coefficient was 3.02 mm/s, which was the highest in this study. The maximum relative errors of the compressive strength calculation model and the permeability coefficient calculation model were only 7.52% and 4.42%, respectively, as shown by the post hoc test. Therefore, I-RAPC has the advantages of high strength and permeability and is expected to be applied in low-impact development in cities with heavy surface sediment content and rainfall.
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The southwestern region of China is the largest exposed karst area in the world and serves as an important ecological security barrier for the upstream of Yangtze River and Pearl River. Different from the critical zone of non-karst areas, the epikarst, formed by an interwoven network of denudation pores, is the core area of karst critical zone. Water is the most active component that participates in internal material cycle and energy flow within the critical zone. We reviewed relevant research conducted in the southwestern region from three aspects: the characte-rization of critical zone structure, the hydrological processes of soil-epikarst system, and their model simulations. We further proposed potential research hotpots. The main approach involved multi-scale and multi-method integrated observations, as well as interdisciplinary collaboration. Precisely characterizing the eco-hydrological processes of the vegetation-soil-epikarst coupling system was a new trend in the future research. This review would provide scientific reference for further studies on hydrological processes in critical zones and regional hydrological water resource management in karst areas.
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Ecossistema , Hidrologia , China , Solo/química , Movimentos da Água , Rios , Água Subterrânea , Conservação dos Recursos Hídricos/métodos , Monitoramento AmbientalRESUMO
Investigations regarding the preparation and durability of cement-based materials applied in specific coastal acid rain environments are scarce, particularly those involving the addition of four auxiliary cementitious materials (ACMs) to cement for modification. To improve the durability of concrete structures in coastal acid rain areas, a systematic study was conducted regarding the preparation of high-strength and corrosion-resistant cement-based materials using ACM systems composed of fly ash (FA), granulated blast furnace slag (GBFS), silica fume (SF), and desulfurization gypsum (DG) instead of partial cement. Through an orthogonal experimental design, the effect of the water-binder ratio, cementitious ratio, and replacement cement ratio on the compressive strength, corrosion resistance coefficient, and chloride ion permeability coefficient of the materials were analyzed and the mix proportions of the materials were evaluated and optimized using the comprehensive scoring method. The results show that implementing a FA:GBFS:SF:DG ratio of 2:6:1:1 to replace 60% of cement allows the consumption of calcium hydroxide crystals generated through cement hydration, promotes the formation of ettringite, optimizes the pore structures of cementitious materials, and improves the compressive strength, acid corrosion resistance, and chloride ion permeability of the materials. This study provides a reference for selecting concrete materials for buildings in coastal acid rain environments.
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The impacts of various aggregate particle sizes and cement contents on the internal structure of pervious concrete were investigated. Accordingly, test blocks with different aggregate particle sizes and cement contents were dissected and photographed. Subsequently, the captured images were processed using the ImageJ software (1.53i) to analyze the profiles of the test blocks and identify the internal mesoscopic parameters of the pervious concrete. This study discusses the relationship between microscopic parameters and macroscopic factors based on experimental results. It also fits functional equations linking the permeability coefficient with pore parameters, matrix parameters, and compressive strength. The results indicated that, as the aggregate size increased, the internal pore diameter of the pervious concrete increased, whereas the total area and width of the cement matrix decreased. This resulted in a low permeability coefficient and high compressive strength of the test block. Increasing the cement content in pervious concrete reduced the porosity and increased the width and area of the internal matrix. Consequently, the permeability coefficient decreased, and the compressive strength of the test block increased.
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It is unknown whether Ferronickel slag (FNS)-ordinary Portland cement (OPC)-based pervious concrete (FOPC) is feasible. To this end, a feasibility study was conducted on FOPC. Firstly, a detailed microscopic examination of the FNS powder was conducted, encompassing analyses of its particle size distribution, SEM, EDS, and chemical composition. These analyses aimed to establish the suitability of a composite of FNS and OPC as a composite cementitious material. Subsequent experimentation focused on evaluating the compressive strength of the composite paste material with varying mixed proportions, revealing a slight reduction in strength as the FNS substitution rate increased. Furthermore, the study designed eighteen different mix proportions of FOPC to investigate the key physical properties, including porosity, density, compressive strength, and the coefficient of permeability. Findings indicated that increases in the cementitious material proportion correlate with enhanced concrete strength, where the ratio of cementitious to aggregate increased by 6.7% and 16.5%, and the strength of FOPC increased by 10-13% and 30-50%, respectively. Conversely, a rise in the FNS substitution rate led to a reduction in compressive strength across different mix ratios. Additionally, the ratio of paste material to aggregate was found to significantly influence the permeability coefficient. These comprehensive performance evaluations suggest that incorporating FNS into OPC for pervious concrete applications is a feasible approach, offering valuable insights for the promotion of waste reuse and the advancement of energy conservation and emissions reduction efforts.
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The objective of this study is to formulate vegetated light porous concrete (VLPC) through the utilization of various cementing materials, the design of porosity, and the incorporation of mineral additives. Subsequently, the study aims to assess and analyze key properties, including the bulk density, permeability coefficient, mechanical characteristics, and alkalinity. The findings indicate a linear decrease in the volume weight of VLPC as the designed porosity increases. While higher design porosity elevates the permeability coefficient, the measured effective porosity closely aligns with the design values. The examined VLPC exhibits a peak compressive strength of 17.7 MPa and a maximum bending strength of 2.1 MPa after 28 days. Notably, an escalation in porosity corresponds to a decrease in both the compressive and the bending strength of VLPC. Introducing mineral additives, particularly silicon powder, is shown to be effective in enhancing the strength of VLPC. Furthermore, substituting slag sulfonate cement for ordinary cement significantly diminishes the alkalinity of VLPC, resulting in a pH below 8.5 at 28 days. Mineral additives also contribute to a reduction in the pH of concrete. Among them, silica fume, fly ash, fly ash + slag powder, and slag powder exhibit a progressively enhanced alkaline reduction effect.
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Organophosphate esters (OPEs) are a group of pollutants that are widely detected in the environment at high concentrations. They can adversely affect human health through multiple routes of exposure, including dermal uptake. Although attention has been paid to achieving an accurate and complete quantification of the dermal uptake of OPEs, existing evaluation methods and parameters have obvious weaknesses. This study reviewed two main categories of methodologies, namely the relative absorption (RA) model and the permeability coefficient (PC) model, which are widely used to assess the dermal uptake of OPEs. Although the PC model is more accurate and is increasingly used, the most important parameter in this model, the permeability coefficient (Kp), has been poorly characterised for OPEs, resulting in considerable errors in the estimation of the dermal uptake of OPEs. Thus, the detailed in vitro methods for the determination of Kp are summarised and sorted. Furthermore, the commonly used skin membranes are identified and the factors affecting Kp and corresponding mechanisms are discussed. In addition, the experimental conditions, conclusions, and available data on Kp values of the OPEs are thoroughly summarised. Finally, the corresponding knowledge gaps are proposed, and a more accurate and sophisticated experimental system and unknown Kp values for OPEs are suggested.
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Poluentes Ambientais , Retardadores de Chama , Humanos , Monitoramento Ambiental , Ésteres , Retardadores de Chama/análise , Organofosfatos , ChinaRESUMO
Soybean protein isolate (SPI)-stabilized nanoemulsions (NEs) were formulated to encapsulate diosgenin (DIO) to enhance its water solubility and bioavailability. The influence of DIO concentrations on NEs' properties was investigated, and their environmental stability and cell permeability were also assessed. Results demonstrated that DIO significantly affected all the physicochemical properties of NEs. NEs with 1.0 mg/mL of DIO exhibited smaller droplet size (209 nm), lower polydispersity index (0.17), and higher stability coefficient (95.8 %). Furthermore, DIO-SPI NEs displayed better stability under appropriate pH (<4 or > 5), NaCl concentrations (≤0.3 M), temperatures (≤60 °C), and freeze-thaw cycles (≤2), as well as storage at 4 °C. Moreover, encapsulating DIO in NEs reduced its toxicity towards cells and enhanced its transport efficiency, which reached 3.16 â¼ 4.87 × 10-6. These findings highlight the potential of SPI-based NEs as a promising carrier for the efficient delivery of DIO.
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Permeability has an important effect on drug absorption. In this study, the effect of different concentrations of sodium sulfobutyl ether-ß-cyclodextrin (SBE-ß-CD) on the absorption of ranitidine was investigated to examine the mechanism of permeability changes. The results of a parallel artificial membrane permeability assay (PAMPA) showed that increasing the concentration of sodium sulfobutyl ether-ß-cyclodextrin, 0, 0.12% (w/v), 0.36% (w/v) and 3.6% (w/v), respectively, caused the apparent permeability coefficient of ranitidine to decrease to 4.62 × 10-5, 4.5 × 10-5, 3.61 × 10-5 and 1.08 × 10-5 in Caco-2 cells, respectively. The same results were obtained from an oral pharmacokinetic study in rats. Further studies indicated that SBE-ß-CD significantly increased the zeta potential of ranitidine. SBE-ß-CD interacted with ranitidine charges to form a complex that reduced ranitidine permeability, and SBE-ß-CD should be chosen with caution for drugs with poor permeability.
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The potential impact of heavy metal ion infiltration on macroscopic and microscopic soil properties is a subject of academic interest. Laterite has an extensive distribution in southern China and is extensively utilized as a vertical containment wall for landfills. Consequently, there is a need to investigate how heavy metal ions affect laterite's microstructure and mechanical properties. To examine the impact of Cu2+ on laterite's microporous characteristics and mechanical properties, laboratory tests were conducted on the permeability, shear strength, microporous characteristics, and strong absorbed water content of Cu2+-contaminated laterite. The results show that Cu2+ hydrolysis generates an acidic environment, which leads to erosion of the cementing substance between the laterite particles, increasing the laterite's porosity and decreasing the soil's cohesive strength, thus affecting the shear strength and permeability of the laterite. When the concentration of Cu2+ is 5.0 g/L, the laterite demonstrated the most significant decrease in shear strength, 43.01%, while the permeability coefficient increased from 3.24 × 10-8 cm/s to 1.32 × 10-7 cm/s. Meanwhile, Cu2+ changes the content of strong absorbed water in laterite. The change of strong absorbed water content will affect the Van der Waals between laterite particles, promote the evolution of soil micropore structure, and lead to a decrease in the proportion of intra-aggregate pores (d < 1 µm) and an increase in the proportion of inter-aggregate pores (1 µm < d < 10 µm), which in turn affects the macroscopic shear strength and permeability. This study has improved our understanding of the mechanisms underlying the microporosity and mechanical property evolution of laterite when subjected to heavy metal attack.
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Metais Pesados , Poluentes do Solo , Cobre/química , Poluentes do Solo/análise , Solo/química , ÁguaRESUMO
The permeability coefficient of construction materials plays a crucial role in engineering quality and durability. In this study, a microstructure model based on real aggregate shape and digital image technology is proposed to predict the permeability coefficient of concrete. A two-dimensional, three-component finite element model of cement concrete was established considering the interfacial transition zone (ITZ) between aggregate and mortar. The permeability coefficient prediction model was developed by the finite element method. The accuracy of the model was verified by experimental data, and the influence of the water-cement ratio on the permeability coefficient of concrete was analyzed. The results show that this method has good prediction accuracy with a relative error of 1.73%. According to the verified model, the influences of aggregate content, aggregate characteristics, aggregate location, ITZ thickness, and other factors on the permeability of concrete were explored. The higher the water-cement ratio, the higher the permeability coefficient. With the increase in aggregate content, the permeability coefficient decreases. Aggregate permeability has a significant influence on the effective permeability coefficient of concrete within a certain range. The greater the roundness of aggregate, the greater the permeability of concrete. On the contrary, the larger aggregate size causes lower permeability. The permeability coefficient of concrete with segregation is lower than that with uniform distribution. At the same time, the permeability increases with the increase of ITZ thickness.
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This study aims to achieve the sustainable utilization of waste glass resources through an investigation into the influence of three types of admixtures, namely waste glass powder (WGP) (G), waste glass powder-slag (G-S), and waste glass powder-fly ash (G-F), on the mechanical properties and durability performance of waste glass concrete. The experimental results demonstrate that the exclusive use of WGP as an admixture led to the relatively poor early compressive strength of the concrete, which decreased with an increase in dosage. However, at medium to long curing ages, the strength of the waste glass concrete could equal or even surpass that of ordinary concrete. When dual admixtures were employed, the G-S group exhibited higher compressive strength compared to the G-F group. Specifically, within the G-S group, a glass powder dosage of 15% yielded higher compressive strength, and after 180 days, the dual admixture groups exhibited greater strength than ordinary concrete (G0); the compressive strength of the tG1S1 group was 44.57 MPa, and that of the G0 group was 40.07 MPa. The chloride ion diffusion coefficient showed a varying trend with an increase in WGP dosage, initially decreasing and then increasing. The concrete's resistance to erosion was maximized when the glass powder dosage reached 30%. As the WGP dosage increased, the overall frost resistance decreased. For a total dosage of 30%, the optimal glass powder dosage in both G-S and G-F groups was found to be 15%.
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In order to improve the mechanical properties and deformation characteristics of permeable concrete, glass fiber was added to this type of concrete. Based on an unconfined compressive strength test, non-contact full-field strain measurement system, and scanning electron microscopy test, the effects of aggregate particle composition, shaking time, fly ash content, fiber length, and fiber content on the strength and permeability of permeable concrete were studied. The results show that the strength and water permeability of permeable concrete are negatively correlated with an increase in shaking time. When the aggregate particle size is 5-10 mm, the permeable concrete has both good strength and permeability. Proper incorporation of fly ash improves the compactness inside the structure. The influence of different lengths of glass fiber on the strength of permeable concrete first increases and then decreases, and the permeable property decreases. With the same fiber length, the strength increases first and then decreases with an increase in the content, while the porosity and water permeability coefficient decrease. Under the test conditions, when the length of glass fiber is 6 mm, and the dosage is 2 kg/m3, the strength performance of permeable concrete is the best, and the permeability effect is good at the same time.
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Acrylic materials exhibit favorable grouting repair performance. However, their curing products are easily inclined to drying shrinkage, and their concrete impermeability repair characteristics have seldom been investigated. To improve material properties, reveal the impermeability repair mechanism, and address drying shrinkage, this study proposed the addition of styrene-acrylate copolymer emulsion (styrene-acrylic emulsion) to the grouting material to prepare two-component acrylate grouting materials. Using orthogonal and single-factor tests combined with physical and mechanical properties, the mechanical properties and impermeability repair performance (physical and mechanical properties combined) of grouting materials were analyzed and studied, and the optimal ratio of each component of acrylate grouting materials was determined. Results show that (1) the hydrogel produced by the reaction of sodium methacrylate with hydroxyethyl acrylate has good physical and mechanical properties. (2) With the increase in the accelerator dosage, the setting time of slurry initially decreases and then increases; as the initiator dosage increases, the setting time of slurry decreases, which is negatively correlated with the initiator dosage. (3) Talcum powder can improve the physical and chemical properties of gel and enhance the reliability and durability of acrylate grouting materials, and the comprehensive performance is the best at a dosage of 3%. (4) Styrene-acrylic emulsion can increase the solid content and reduce the volume drying shrinkage when added to grouting materials. The fractured impermeable specimens were repaired by grouting with prepared acrylate grouting materials and cured for 24 h for the impermeability test, and the water pressure for the 24 h impermeability repair was 1.0 MPa. This study's results provide important reference and basis for revealing the impermeability principle of acrylate grouting materials and evaluating their impermeability.
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In order to solubilize poorly soluble active pharmaceutical ingredients, various strategies have been implemented over the years, including the use of nanocarriers, such as cyclodextrins and liposomes. However, improving a drug's apparent solubility does not always translate to enhanced bioavailability. This work aimed to investigate to which extent complexation with cyclodextrins and incorporation into liposomes influence drug in vitro permeability and to find a mechanistic description of the permeation process. For this purpose, we investigated hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and phosphatidylcholine liposomes formulations of three chemically diverse compounds (atenolol, ketoprofen and hydrocortisone). We studied drug diffusion of the formulations by UV-localized spectroscopy and advanced data fitting to extract parameters such as diffusivity and bound-/free drug fractions. We then correlated this information with in vitro drug permeability obtained with the novel PermeaPadâ barrier. The results showed that increased concentration of HP-ß-CD leads to increased solubilization of the poorly soluble unionized ketoprofen, as well as hydrocortisone. However, this net increment of apparent solubility was not proportional to the increased flux measured. On the other hand, normalising the flux over the empirical free drug concentration, i.e., the free fraction, gave a meaningful absolute permeability coefficient. The results achieved for the liposomal formulation were consistent with the finding on cyclodextrins. In conclusion, we proved the adequacy and usefulness of our method for calculating free drug fractions in the examined enabling formulations, supporting the validity of the established drug diffusion/permeation theory that the unbounded drug fraction is the main driver for drug permeation across a membrane.
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Ciclodextrinas , Cetoprofeno , beta-Ciclodextrinas , Ciclodextrinas/química , Lipossomos/química , 2-Hidroxipropil-beta-Ciclodextrina , beta-Ciclodextrinas/química , Cetoprofeno/química , Hidrocortisona/química , PermeabilidadeRESUMO
Hydraulic structures are typically subjected to long-term hydraulic loading, and concrete-the main material of structures-may suffer from cracking damage and seepage failure, which can threaten the safety of hydraulic structures. In order to assess the safety of hydraulic concrete structures and realize the accurate analysis of the whole failure process of hydraulic concrete structures under the coupling effect of seepage and stress, it is vital to comprehend the variation law of concrete permeability coefficients under complex stress states. In this paper, several concrete samples were prepared, designed for loading conditions of confining pressures and seepage pressures in the first stage, and axial pressures in the later stage, to carry out the permeability experiment of concrete materials under multi-axial loading, followed by the relationships between the permeability coefficients and axial strain, and the confining and seepage pressures were revealed accordingly. In addition, during the application of axial pressure, the whole process of seepage-stress coupling was divided into four stages, describing the permeability variation law of each stage and analyzing the causes of its formation. The exponential relationship between the permeability coefficient and volume strain was established, which can serve as a scientific basis for the determination of permeability coefficients in the analysis of the whole failure process of concrete seepage-stress coupling. Finally, this relationship formula was applied to numerical simulation to verify the applicability of the above experimental results in the numerical simulation analysis of concrete seepage-stress coupling.