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The seismic response of seabed is fundamental for researching the seismic response of marine structures. The one-dimensional transient response of an unsaturated seabed was studied in this paper. An analytical solution for a special case with infinite permeability coefficients and a semianalytical solution for a general case with arbitrary permeability coefficients were developed. The advantage of this semianalytical solution is that it can compute the behavior of unsaturated soils with very low permeability coefficients. During the derivation, the boundary conditions were transformed into homogeneous boundary conditions first, and then the eigenvalues and eigenfunctions were obtained. To obtain solutions in the time domain, the eigenfunction expansion method and the precise time-step integration method were employed. Through numerical examples, the reflection and transmission characteristics of three types of compression waves at the fluid–solid interface were elucidated. The impact of permeability coefficients and water saturation on the seismic response of the seabed was investigated through parametric analysis. When the soil is nearing saturation, even a slight change in saturation can lead to a drastic alteration in the seismic response of the nearly saturated seabed. [ABSTRACT FROM AUTHOR]

To improve their permeability,porous Si3N4 ceramics were prepared using Si powder as the raw material,Y2O3 and CaF2 as sintering aids,and polymethyl methacrylate microspheres (5 and 20 μm) as pore-forming agents, gel-casting, binder-removing, and finally reaction sintering at 1 650 °C for 3 h in a nitrogen atmosphere. The effects of the particle sizes and additions (volume fractions of 0,15%, 30%, 45%, and 60%) of the pore-forming agents on the apparent porosity,pore size distribution,pore structure and permeability coefficient of the porous Si3N4 ceramics were studied. The results show that: (1) the samples with pore agents exhibit dual pore structures, which are composed of stacking-derived pores and spherical evolution pores, with bimodal pore size distribution; (2) with the same particle size,as the pore-forming agent addition increases,the apparent porosity and permeability coefficient of the samples increase,while the bulk density, bending strength, and fracture toughness decrease; (3) at the same addition, the samples with the smaller-sized agents (5 μm) have higher apparent porosity,permeability coefficient,and bending strength;using smaller-sized pore-forming agents can reduce the thickness of the pore walls and enlarge the pore sizes of the stacking-derived pores within the pore walls,thus enhancing the permeability of the pore walls; (4) the sample with 60% pore-forming agents of 5 μm has the best comprehensive performance,with the apparent porosity of 55.1%,permeability coefficient of 11.62x10-14 m² and bending strength of 35.3 MPa. [ABSTRACT FROM AUTHOR]

The density of rockfill material is an important index to evaluate the quality of rockfill dams. It is of great significance to accurately obtain the densities and permeability coefficients of rockfill material dams quickly and accurately by scientific means. However, it takes a long time to measure the permeability coefficient of rockfill material in practice, which means that such measurements cannot fully reflect all the relevant properties. In this paper, using a convolutional neural network (CNN), a machine learning model was established to predict the permeability coefficient of rockfill material with the full scale (d10~d100), pore ratio, Cu, and Cc as the inputs and the permeability coefficient as the output. Through collecting the permeability coefficient and related data in the literature, the set samples were sorted for model training. The prediction results of the trained CNN model are compared with those of the back propagation (BP) model to verify the accuracy of the CNN model. Laboratory constant head penetration experiments were designed to verify the generalization performance of the model. The results show that compared with the BP model, the CNN model has better applicability to the prediction of the permeability coefficient of rockfill material and that the CNN can obtain better accuracy and meet the requirements of the rough estimation of rockfill materials' permeability in engineering. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The accurate and efficient inversion of permeability coefficients is significant for the scientific assessment of seepage safety in concrete face rockfill dams. In addressing the optimization challenge of permeability coefficients with few samples, multiple parameters, and strong nonlinearity, this paper proposes a novel intelligent inversion method based on the Sobol-IDBO-SVR fusion surrogate model. Firstly, the Sobol sequence sampling method is introduced to extract high-quality combined samples of permeability coefficients, and the equivalent continuum seepage model is utilized for the forward simulation to obtain the theoretical hydraulic heads at the seepage monitoring points. Subsequently, the support vector regression surrogate model is used to establish the complex mapping relationship between the permeability coefficients and hydraulic heads, and the convergence performance of the dung beetle optimization algorithm is effectively enhanced by fusing multiple strategies. On this basis, we successfully achieve the precise inversion of permeability coefficients driven by multi-intelligence technologies. The engineering application results show that the permeability coefficients determined based on the inversion of the Sobol-IDBO-SVR model can reasonably reflect the seepage characteristics of the concrete face rockfill dam. The maximum relative error between the measured and the inversion values of the hydraulic heads at each monitoring point is only 0.63%, indicating that the inversion accuracy meets the engineering requirements. The method proposed in this study may also provide a beneficial reference for similar parameter inversion problems in engineering projects such as bridges, embankments, and pumping stations. [ABSTRACT FROM AUTHOR]

Due to the characteristics of geographical environment and many complicated factors, the seepage properties of calcareous sand are quite different from those of common continental and marine sediments. To investigate the change of permeability coefficient of calcareous sand under external load, a seepage test device equipped with an impact loading system was developed. The effects of particle size distribution, initial relative density and impact load on the permeability of calcareous sand were investigated with this device. The results showed that the larger the curvature coefficient and uniformity coefficient, the smaller the initial relative density lead to the greater the permeability coefficient of calcareous sand and the more obvious the change of permeability coefficient before and after loading. The permeability change of calcareous sand under impact load was greater than that of quartz sand. [ABSTRACT FROM AUTHOR]

The saturated permeability coefficient (ks) is a key parameter for evaluating the seepage and stability of reservoir colluvial landslides. However, ks values obtained from traditional experimental methods are often characterized by large variations and low representativeness. As a result, there are significant deviations from actual observations when used in seepage field calculations for reservoir landslide analysis. This study proposes an intelligent inversion method that combines a physical model and a data-driven model for reservoir landslide ks based on actual groundwater level (GWL) monitoring data. This method combines Latin Hypercube Sampling (LHS), unsaturated flow finite element (FE) analysis, particle swarm optimization algorithm (PSO), and kernel extreme learning machine model (KELM). Taking the Hongyanzi landslide in Sichuan Province, China, as the research object, the GWL of the landslide under different ks was first obtained by LHS and transient seepage FE analysis. Then, a nonlinear functional relationship between ks and the landslide GWL was fitted based on the PSO-KELM model. Finally, the optimal landslide ks was obtained by minimizing the root-mean-squared error between the predicted and actual GWL using the PSO. A global sensitivity analysis was also conducted on the ks of different rock and soil layers to reveal their control rules on the calculation of landslide GWL. The research results demonstrate the feasibility of the proposed method and provide valuable information for similar landslides in practice. [ABSTRACT FROM AUTHOR]

The coefficient of vertical permeability is a common filter design criterion for woven slit-film geotextiles. According to the pipe flow theory, a permeability coefficient model has been proposed for predicting the permeability coefficient of woven geotextiles, in which the pore characteristics were described by the Sierpiński carpet fractal theory. The verification of models is performed in 12 woven geotextiles of two types using a digital image method and a vertical water permeability test of the geotextile. The influence of the pore characteristics on the permeability coefficient is further explored using univariate and multivariate analyses. The results show that the porosity model can accurately predict the total percent pore area (POA) and the POA distribution of the woven geotextiles, and the permeability model can accurately predict the permeability coefficient of the geotextiles. The permeability coefficient of geotextiles decreases with the pore area fractal dimension and the minimum pore size under the action of a single factor. The permeability coefficient increases as the maximum pore size increases. POA and maximum pore size are the most significant independent variables affecting the permeability coefficients of geotextile under the action of multifactor. [ABSTRACT FROM AUTHOR]

In order to propose an accurate and rapid method for the determination of the permeability coefficient of clay in the core of an earth-rock dam, this paper establishes an ellipsoidal horizontal flow model for the seepage flow based on CPTU, which is suitable for the evaluation of the horizontal permeability coefficient of compacted soil. It firstly reviews the previous research results of soil permeability coefficient estimation based on CPTU, and then, from the practical perspective, analyzes and deduces the simple mechanical model of pore water pressure distribution generated by the soil injected by the probe. After the measured data are compared, it concludes that the distribution of negative exponential function has a strong correctness. Then an evaluation method of permeability coefficient based on ellipsoidal horizontal seepage model is derived. It is proved by an engineering example that the method in this paper improves the previous methods in theory and calculation accuracy, and has a good prospect in engineering application. [ABSTRACT FROM AUTHOR]

Semi-rigid base asphalt pavement (SBAP) has been recognised as an economical and high load-carrying ability pavement and has been practised widely in China. One of its primary deficiencies is water distress. In this study, the permeability detection of SBAP was investigated by infrared thermal difference method (ITDM), in which the permeability and distress evolution characteristics were explored by detecting the temperature difference. The air voids, thermal difference and permeability of asphalt pavement specimens were designed to obtain influence of water volume change on pavement temperature. The field thermal difference tests were performed by special test carriage and pavement distress were measured to obtain permeability responses. The results indicate that during temperature difference increases from 2 $^{\circ }$ ∘ C to 5.9 $^{\circ }$ ∘ C, ITDM will reflect the air voids and permeability coefficient of asphalt pavement. The results also show it takes more than 3 days for the water in the saturated specimens with a permeability coefficient greater than 300 mL/min to evaporate, which is unfavourable to the pavement. Furthermore, the field ITDM experimental results are corresponded well with pavement distress. It is concluded that ITDM is an effective approach for asphalt pavement permeability detection. [ABSTRACT FROM AUTHOR]

One of the problems that limit the development of porous asphalt concrete (PAC) is that the pores become clogged, which leads to severe deterioration in its permeability performance. This paper focuses on PAC's permeability characteristics under repeated cycles of clogging. First, sand (S), clay (C), and sand and clay mixtures (S + C) were used as clogging materials for repeated clogging tests. Then, the permeability coefficients in the initial state and after clogging were measured with an improved permeability device. Based upon porosity, maximum nominal particle size, and clogging materials, the paper analyzed the permeability regulation of PAC under repeated clogging conditions. In addition, we compared the restoration effects of vacuum cleaning, high-pressure cleaning, and surface cleaning with cleaning tests and proposed a response surface methodology prediction model. Finally, the particle size distribution of sensitive particles that cause different porosities in PAC clogging was explored. The results showed that the initial permeability coefficient and the permeability coefficient with PAC's repeated clogging increased with the increase in the nominal maximum particle size and porosity. PAC clogged by sand has the greatest rate of reduction in the coefficient of permeability. In addition, we suggested that in PAC pavement maintenance work, water is first sprinkled to wet the road, then high-pressure cleaning used, and finally vacuum cleaning. The prediction model is reliable and the cleaning method has the most significant effect on the permeability coefficient. Further, the particle size distribution that caused PAC-13 and PAC-10 clogging ranged from 0.15 to 2.36 mm and 0.075 to 2.36 mm, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Landslides are caused by rainfall as one of the main factors. In order to study the effect of rainfall on the physical and mechanical parameters of landslides, a physical model of the colluvium landslide is created in laboratory conditions with silty clay, river sand, and gravel, taking Shuping landslide in the Three Gorges Reservoir area as the prototype. The artificial rainfall is applied to the accumulation model, which is steady for 60 h, and then the gravel soil is taken out along the different elevations of the colluvium for the permeability test and direct shear test, and the evolution law of changes in porosity, the permeability coefficient, and the shear strength parameters along the elevation are studied. Combined with XRF and NMR tests, the spatial variation of the permeability coefficient and shear strength parameters is discussed from the perspective of chemical elements, minerals content, and porosity, and the stability analysis of a colluvium landslide is carried out considering the influence of parameters along the elevation. The results show that under the action of rainfall seepage, the fine particles of clay are transported from upslope to downslope, resulting in more and more fine particles of clay at the toe slope. The original pores are gradually filled, the cementation between particles is stronger, the corresponding cohesion is increased, and the permeability coefficient is reduced. Due to the loss of fine particles at the upslope, the relative content of coarse particles increases, leading to an increase in the internal friction angle. The variability of the slope's physical and mechanical parameters is a result of the spatial transport of clay particles in the colluvium caused by the rainfall seepage above. Specifically, the permeability coefficient and internal friction angle from upslope to downslope decrease linearly under the action of rainfall, but the law of the cohesion increases linearly. The upslope's permeability coefficient and internal friction angle decrease by 11% and 8% compared to those of the downslope, while the cohesion increases by 168%. The results of FLAC3D numerical calculation of Shuping landslide show that the maximum deformation in the X direction of 145 m and 175 m water level increases by 12% and 42%, and the safety factor decreases by 0.63% and 5% under the combined action of rainfall and the reservoir water level, that is, when considering the variation of parameters along the elevation of the landslide. The research findings provide a better understanding of the spatial parameters in similar colluvium bodies under rainfall action. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The permeability of the natural geology plays a crucial role in accurately analyzing seepage behavior in the project area. This study presents a novel approach for the inverse analysis of the permeability coefficient. The finite element model (FEM) combined with orthogonal experimental design is used to construct a sample set of permeability coefficient inversion. The established random forest (RF) algorithm surrogate model is applied to determine the optimal values of permeability parameters in the project area using the Harris hawk optimization (HHO) algorithm. This method was used to explore and verify the distribution of natural seepage fields for the P hydropower station. The results showed that the RF model outperformed the classical CART and BP models at each borehole regarding performance evaluation indices. Furthermore, the water head prediction results were more accurate, and the RF model performed admirably in terms of prediction, anti-interference, and generalization. The HHO algorithm effectively searched for the optimal permeability coefficient of the geology. The maximum value of the relative error of the borehole water head inverted was 1.11%, and the accuracy met engineering standards. The initial seepage field distribution pattern calculated followed the basic distribution pattern of the mountain seepage field. [ABSTRACT FROM AUTHOR]

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To study the fracture propagation mechanism and the permeability evolution of the fault fracture zone in coastal deep mines, the nuclear magnetic resonance (NMR) tests and the triaxial mechanical properties tests of rock specimens rock mass specimens with different joint dip angles under hydro-mechanical coupling were carried out. Based on the investigation of the surrounding rock joints and the analysis of rock composition, the rock physics experimental model was prepared. The evolution mechanism of rock porosity is obtained by NMR test. The changes of mechanical properties, acoustic emission (AE) and permeability characteristics of rock specimens with different joint dip angles were studied, and the evolution mechanism of permeability properties with different joint dip angles is revealed by combining the microstructure and joint tip expansion mechanism. When the jointed rock mass specimens reach the peak stress, the bearing capacity of the specimens decreases slowly, and the specimens show the characteristics of progressive failure. The specimen generates micro-cracks at the joint tip under the action of axial pressure, micro-cracks evolve and expand with the increase of pressure, the permeability coefficient gradually increases. The main fracture of jointed rock mass specimens is the fracture that originates from the joint tip and extends along the axial direction until the specimen loses its bearing capacity. Highlights: Evolution mechanism of permeability properties was revealed. The microstructure and joint tip expansion mechanism were studied. The fracture propagation law of jointed rock mass specimens was investigated. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fine-grained sediments are Quaternary sediments with grain sizes of not more than 2 mm. They start first when meeting water, their stability is related to the initial water volume triggering debris flow, and thus plays an important role in debris flow hazards early warning. The permeability coefficient is the inter-controlled factor of fine-grained sediment stability. However, there is no hyperspectral model for detecting the fine-grained sediment permeability coefficient in large areas, which seriously affects the progress of debris flow hazards early warning. Therefore, it is of great significance to establish a hyperspectral detection model for the permeability coefficient of fine-grained sediments. Taking Beichuan County, Southwestern China as the case, a permeability coefficient hyperspectral detection model was established. The results show that eight bands are sensitive to the permeability coefficient with a correlation coefficient (R) of 0.6343. T-test on the model shows that P-values for sensitive bands are all less than 0.05, indicating the established model has a good prediction ability with a precision of 85.83%. These sensitive bands also indicate the spectral characteristics of the permeability coefficient. Therefore, it provides a scientific basis for fine-grained sediment stability detection in large areas and lays a theoretical foundation for debris flow hazards' early warning. [ABSTRACT FROM AUTHOR]

This study develops a coupled model of chemical clogging and permeability coefficient of geotextile envelope. Based on the distribution characteristics of crystal precipitates on geotextile envelope and their influence on the permeability coefficient, a permeability coefficient model of an actual geotextile envelope that considers the overlapping effect is developed. Then, the densification effects of geosynthetic fiber hypothesis and the filter cake effect hypothesis are proposed to simulate the processes of increasing fiber diameter after crystal precipitation and the accumulation of crystal precipitates on the surface of geotextile envelope. The crystal precipitation module and permeability coefficient module are coupled, and their experimental values are used to confirm the availability of the model. Results indicate the satisfactory performance of the model. In addition, the parameter sensitivity analysis and trend prediction show that the saturation index SI and solution flow rate V are the main factors that affect the chemical clogging and permeability of geotextile envelope. When the solution conditions are not considered, the sensitivity of geotextile envelope parameter d f increased with the amount of precipitation in crystal precipitation. When the pores of the geotextile envelope are completely clogged, the permeability coefficient of the geotextile envelope will drop sharply, then decline slowly. • A coupled model for chemical clogging and permeability coefficient of geotextile envelope is developed. • The densification effect of geosynthetic fiber and the filter cake effect are proposed to generalize chemical clogging. • The sensitivity of geotextile envelope parameter d f increased with the amount of precipitation. [ABSTRACT FROM AUTHOR]

In the construction of artificial islands in distant seas, calcareous sand has been widely used as a foundation filler due to its excellent mechanical properties and extensive availability in the marine environment. How to store more fresh water on the artificial islands by reducing its permeability is currently a great challenge. Microbial-induced carbonate precipitation (MICP) has always been considered as a great potential method to improve the cemented properties of calcareous sand, but the effect of grain gradation on the permeability of MICP-improved calcareous sand remains unclear. In this research, a self-made device was developed to conduct MICP grouting and permeability tests, where the permeability coefficient (k) under different grain gradations (curvature coefficient (Cc) and uniformity coefficient (Cu)) was measured. A CT scan was conducted to investigate the variation in the porosity (n) of sand samples before and after MICP treatment. The weighting method was adopted to measure the content of induced calcium carbonate (M). A scanning electron microscopy (SEM) technique was used to further study the micromechanism of the MICP treatment. Finally, the correlations between the k of MICP-treated sand and Cu, as well as Cc, were semiquantitively analyzed. The results show that the magnitude of M, k and n changes are closely related to Cc and Cu. The reduction amount of k and n increased with the rise in Cc and Cu, and the increased amount of M increased with the rise in Cc and Cu. The SEM results show that the particle surface became rough due to the coating effect of CaCO3 crystals, and the pore spaces were reduced because of the partially filling effect of the crystals, which was responsible for the decrease in permeability and porosity. Furthermore, k fitted well with Cu and Cc, respectively, and the fitting curve reveals that larger Cu (Cu ≥ 6.0) and smaller Cc (2.0 > Cc > 0.5) were more suitable for MICP treatments and lead to a large reduction in permeability. The above results indicate that the grain gradation of calcareous sand had a significant influence on its permeability improved by MICP. [ABSTRACT FROM AUTHOR]

Homogeneous films of polynaftoylenebenzimidazole (PNBI-σ) were obtained by two-stage synthesis from prepolymer films by thermal cyclization at 350 °C. The presence of micropores in PNBI-σ films is shown by the method of CO 2 sorption, the micropore specific surface area is 285 m2/g. Gas permeability of He, H 2 , CO 2 , CH 4 , O 2 and N 2 was studied by differential gas chromatographic method in the temperature range of 50–250 °C, and the activation energies of permeability were determined. At 250 °C, hydrogen permeability coefficient of 220 Barrers and ideal selectivity of 17 for H 2 /CO 2 were achieved, which significantly exceeds the values for the upper bound of 2008 Robeson diagram. The analysis of permeability of the components of mixtures of gases H 2 /CO 2 and H 2 /CH 4 of various compositions at 250 °C showed that with a decrease in the concentration of the sorbed component (CO 2 or CH 4) a sharp increase in the separation factor is observed. When the composition of the H 2 /CO 2 mixture is 70/30, the H 2 /CO 2 separation factor increases by more than an order of magnitude compared to the selectivity for individual gases while the hydrogen flow is maintained. The obtained experimental data demonstrate the capabilities of PNBI-σ for high-temperature separation processes, including the separation of industrial hydrogen-containing mixtures. [Display omitted] • The gas separation properties of PNBI-σ were studied in wide temperature range. • P(H 2) of 220 Barrers and α(H 2 /CO 2) of 17 were achieved at 250 °C for pure gases. • High separation factors for H 2 /CO 2 and H 2 /CH 4 mixtures were achieved. • At 250 °C and CO 2 content less than 30 % the separation factor was at least 900. [ABSTRACT FROM AUTHOR]

The main objective of the present research study was to predict the permeability of concrete with mineral ultrafine additions by using artificial neural networks. Concrete mixtures were prepared without addition (4) and with additions of metakaolin (1), microsilica (2), and pozzolan (3). The results showed that permeability values ranged between [0.12, 733]x10-13 m/s. Using the ordinary analysis of variances, it was established that at 28 days the permeability of concrete stabilizes with the additions of (2) and (3), but not with the addition of (1). Different artificial neural network architectures were tested, obtaining correlations in the simulation phase from 0.904 to 0.907. In addition, neural networks were obtained that made feasible to safely predict permeability coefficients for added concrete. It is concluded that additions (2) and (3) have an inverse effect on the permeability of concrete, reaching stability after 28 days. [ABSTRACT FROM AUTHOR]

Soil treated with silicone hydrophobic material for a long time can effectively improve the saturated permeability of the ground, which has been confirmed. However, the long time will increase the cost in engineering construction. Secondly, the mechanism of alteration of soil–water properties by silicone hydrophobic materials is not understood. This lack of understanding is not conducive to the engineering application of silicone hydrophobic materials. Therefore, variable-head permeability and matrix suction tests under 15 different test conditions were conducted with different hydrophobic material dosage and action time as variables in this paper. The soil–water characteristic curve (SWCC) was plotted according to the test results, the unsaturated permeability coefficient was calculated, and curve fitting was performed. It can be seen from the test data that, with the increase in the dosage of hydrophobic materials and the action time, the permeability coefficient and the air-entry value showed a downward trend. Nevertheless, as the reaction proceeded, a mutation occurred at 4 h. When the minimum dosage and action time were used, the soil's permeability coefficient and air-entry value decreased by 80.65% and 71.09%. The test results show that, even when the action time was 2 h, the hydrophobic material could maintain the permeability of the soil and reduce its air-entry value; thus, the hydrophobic material could effectively reduce the rise of capillary water in the soil and protect the roadbed. [ABSTRACT FROM AUTHOR]

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Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Suffusion is a typical type of internal erosion that is an important factor leading to the failure of dams and dikes. In this paper, fine particles are divided into erodible particles and non-erodible particles, and the soil suffusion mechanism is investigated by laboratory tests and CFD_DEM simulations when the content of erodible particles (Fc) and non-erodible particles (Fz) is 15% and 5%, 10% and 10%, and 5% and 15%. The global mean permeability coefficient (kav) and local permeability coefficient (ki–j) were calculated by monitoring the water head in the seepage path of the sample. The results show that with increasing non-erodible particle content, the difficulty of soil suffusion increases gradually. When soil suffusion occurs, the loss of fine particles starts from the seepage outlet area and the influent area, and the non-erodible particles have little influence on the particle loss process in these two areas. After the occurrence of suffusion, the number of weak contact chains is obviously reduced, while the strong contact chains are basically stable. When Fz = 5% and Fz = 10%, the average permeability coefficient of the soil after suffusion expands to 2.21–1.60 times that of the initial state, and the corresponding values of the CFD_DEM simulation are 2.14–1.86 times. [ABSTRACT FROM AUTHOR]

The calcium leaching effect leads to a decrease in the impermeability of the impervious curtain. The inverse analysis strategy was introduced in this study because the calcium leaching parameters of the curtain are not easy to determine. An orthogonal design and the finite element method were used in the strategy. The time-series data of hydraulic head and leakage volume were applied to construct the objective function. The extreme learning machine (ELM) was proposed to build the reflection sets. Genetic algorithm (GA), simulated annealing (SA), sparrow search algorithm (SSA), and particle swarm optimization (PSO) were employed to accelerate the iterative search for the target parameters. The target parameters of the calcium leaching model were used for finite element verification by comparing the monitored and simulated values. The simulated values of hydraulic head and leakage by PSO show good agreement with measurements. The evolution of the curtain permeability coefficient in 100 years was analyzed. The results demonstrate the strategy's feasibility in determining the curtain's calcium leaching parameters and permeability coefficients. [ABSTRACT FROM AUTHOR]

Fine sediments in debris-flow gullies are quaternary sediments with a particle size of less than 2 mm. Since they are easy to suspend in flowing water, their stability plays a key "probe" role in early debris-flow warning. The permeability coefficient is the main internal control factor of fine sediment stability in debris flow. However, there is no quantitative model between the permeability coefficient and its influencing factors, which seriously affects the quantitative evaluation of debris flow sediments. Taking the debris-flow gullies in Laobeichuan County, Sichuan Province, China as the research area, we carried out experiments on the permeability coefficient and its influencing factors. A model between the permeability coefficient and its influencing factors was established by the least-squares multivariate statistical analysis method. The results showed that cohesion was the closest factor to the permeability coefficient, followed by porosity and density. Each factor passed the t-test and significantly correlated with the model in 99.99% probability. With a correlation coefficient of 0.72, the model had a good prediction ability. Therefore, the model not only provides a theoretical basis for analyzing the stability of fine sediments in Laobeichuan County, but also points out the direction for detecting the fine sediment stability in debris-flow gullies. [ABSTRACT FROM AUTHOR]

Purpose: The tissue-to-plasma partition coefficient (Kp) describes the extent of tissue distribution in physiologically-based pharmacokinetic (PBPK) models. Constant-rate infusion studies are common for experimental determination of the steady-state Kp,ss, while the tissue-plasma concentration ratio (CT/Cp) in the terminal phase after intravenous doses is often utilized. The Chen and Gross (C&G) method converts a terminal slope CT/Cp to Kp,ss based on assumptions of perfusion-limited distribution in tissue-plasma equilibration. However, considering blood flow (QT) and apparent tissue permeability (fupPSin) in the rate of tissue distribution, this report extends the C&G method by utilizing a fractional distribution parameter (fd). Methods: Relevant PBPK equations for non-eliminating and eliminating organs along with lung and liver were derived for the conversion of CT/Cp values to Kp,ss. The relationships were demonstrated in rats with measured CT/Cp and Kp,ss values and the model-dependent fd for 8 compounds with a range of permeability coefficients. Several methods of assessing Kp were compared. Results: Utilizing fd in an extended C&G method, our estimations of Kp,ss from CT/Cp were improved, particularly for lower permeability compounds. However, four in silico methods for estimating Kp performed poorly across tissues in comparison with measured Kp values. Mathematical relationships between Kp and Kp,ss that are generally applicable for eliminating organs with tissue permeability limitations necessitates inclusion of an extraction ratio (ER) and fd. Conclusion: Since many different types/sources of Kp are present in the literature and used in PBPK models, these perspectives and equations should provide better insights in measuring and interpreting Kp values in PBPK. [ABSTRACT FROM AUTHOR]

Air penetration behavior plays a vital role in the performance of fibrous material in various industrial applications. Two parameters, the permeability coefficient and airflow resistivity, can describe the air penetration behavior of fibrous material. FX 3300 Textech Tester III and AFD300 AcoustiFlow devices were used to respectively characterize the permeability coefficient and airflow resistivity of nonwoven materials. Nonwoven samples were compressed due to the load from the test head of the FX 3300. Finite element analysis along with the mathematical method were implemented to recover the airflow permeability of samples at the uncompressed state. The effects of pressure drop on the airflow velocity and permeability coefficient were analyzed by the Ergun-type model. The determination of airflow resistivity based on the permeability coefficient is carried out via two approaches, that is, the direct method and the extrapolation method. The results show that the airflow velocity is not linearly related to the pressure drop, which differs from Darcy's law. This non-linear relation is mainly attributed to the influence of frictional loss. By comparing the relative error between assessed and measured airflow resistivity, most of the assessed values of the compressed samples are overestimated. The results also suggest that the direct and extrapolation methods are applicable to assess airflow resistivity on an airflow velocity (or air permeability) test device. Moreover, the Ergun-type model is also applicable to determine the permeability coefficient and airflow resistivity of nonwoven materials. [ABSTRACT FROM AUTHOR]

There are abundant oil resources in Xinjiang, and the exploitation of oil resources could easily pollute the soil. In this paper, the impact of oil pollution on permeability of the gray desert soil affected by freeze-thaw cycles under a dry and cold climate of Karamay region in Xinjiang was studied. First, varying-head infiltration tests were conducted on soil samples with different water contents and pollution intensity without exposing to freeze-thaw cycles. The variability of permeability were analyzed employing the scanning results of the polluted soil samples by an electron microscope. Then several freezing and thawing cycle tests were implemented on the samples. The test results shown that the soil permeability was optiomal and the permeability coefficient was highest when the crude oil pollution intensity was 0.61% and the water content was 15.53%. With the water content in soil samples being the same, the soil permeability coefficient increased in the beginning and then decreased as the pollution intensity increased. When the pollution intensity ranging from 0.5% to 1.75%, the freezing and thawing condition could be the leading factor affecting the soil permeability. However, when the oil content was within the range of 1.81% – 2.41%, the freezing and thawing condition could not be the leading factor affecting the soil permeability. The results provided in this study could serve as a relevant basis for the remediation of soil pollution in oil production plants in arid areas of Western China. [ABSTRACT FROM AUTHOR]

The mechanical dehydration method is generally used for reducing the moisture content in sludge. However, there is little understanding of the physical and mechanical properties and dehydration mechanism of sludge during pressurization. In this paper, characteristics of sludge were studied from the perspective of soil mechanics. The water permeability, loading conditions, and dehydration performance of the sludge during the pressurization process were analyzed through a series of geotechnical laboratory experiments. The results showed that the pore structure, compressibility coefficient, consolidation coefficient, and permeability coefficient of the sludge are related to the dehydration rate. The conditioners that mixed with sludge could increase the dewatering rate by reducing the sludge viscosity, changing the water status, and increasing the permeability coefficient. The two conditioners used in this study increased the dehydration rate of the sludge from 27.5 to 52.6% and 63.9%, respectively. Unlike the seepage consolidation of ordinary clay, which has only one stage, the seepage consolidation of sludge could be divided into three stages. The removed water in the first stage is mainly free water; the discharge in the second stage is the combination of free water and bound water, and bound water was mainly discharged in the third stage. The water content at the end of each stage corresponds to the liquid limit, plastic limit, and shrinkage limit of the sludge. Our study provides a novel insight for understanding the deep dewatering of sludge and is benefit to solve the problem of sludge dewatering. [ABSTRACT FROM AUTHOR]

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Three rows of high-pressure rotary jet interlocking pile water stop curtain are adopted at the junction of the island and tunnel on the west artificial island of Shenzhen-Zhongshan Link. After removing the steel cylinder retaining structure at the island head, the underground waterproof function can be realized. In order to further study the sealing performance of the waterproof curtain, the overall permeability of the waterproof curtain was tested by carrying out large-scale water tight tests to verify the rationality of its design and safety in use. It is compared with the conventional borehole water injection test. The test results show that the permeability coefficient of the waterproof curtain verified by the large-scale water tight test is basically consistent with that of the conventional water injection method, which provides a reference for similar projects. [ABSTRACT FROM AUTHOR]

The permeability property of a packed particles material has been caught much attention, it depends upon its pore characteristics caused by the particle accumulation, but the current empirical formulas and the permeable theory could not reveal the effect of the particle accumulation thoroughly. In this paper, a theoretical formula is derived, and the fractal gradation spectrum is adopted to confirm the particle size distribution, furthermore, the pore feature is determined by the particle size and accumulation features, finally a permeability model of the packed particles material is established. In this model, the effect of particle size distribution on pore features is estimated more thoroughly than those in conventional models, and the calculated results are more accurate and verified experimentally. [ABSTRACT FROM AUTHOR]

Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb2+) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb2+ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement. [ABSTRACT FROM AUTHOR]

Reservoir dams have varying degrees of damage and hidden dangers under long-term and complex operating conditions, engineering problems mainly focus on the gradual decrease of seepage stability and guarantee rate of deformation and stability of dam foundation. However, due to the complexity of the dam foundation structure and the surrounding environment, the performance degradation of the dam foundation caused by the aging of the impervious structure lacks a systematic study of the process and its mechanism, In particular, the determination of relevant seepage parameters is complicated, moreover the simulation accuracy of its inversion model is not enough to meet the needs of long-term stability evaluation of the dam foundation. In order to study the seepage stability of the dam foundation of the reservoir during operation, a three-dimensional finite element model of complex geological bodies is combined with artificial neural network to establish a model of inversion of seepage field in the dam foundation, According to the 22 groups of predicted grouting schemes, five groups of representative grouting schemes were selected and the seepage characteristics of the same location were analyzed. The conclusions as below: (1) the inversion predicted that when the permeability coefficient was in the range of 3.0 × 10−6 cm/s to 5.0 × 10−6 cm/s, the change range was small, and the curtain's anti-seepage effect was more obvious. (2) The analysis of the dam base surface and the bottom of the grouting area shows that the difference between the water head and seepage gradient of the dam base surface and the bottom of the grouting area under the GZ 7 and GZ 3 schemes vary significantly with the grouting effect. Among them, especially in the GZ 3 scheme, the key parts of the dam foundation surface F2 ~ F4: the seepage gradient value gradually increases, and all reach the maximum value in the GZ 3 scheme; For G6 ~ G15 at the bottom of the grouting area, the water head value under the GZ 3 scheme is gradually smaller than the three grouting schemes of GZ 11 , GD 3 and GD 7 , as the water head value gradually decreases, the anti-seepage effect becomes more and more obvious. The above results show that the inversion prediction range is in good agreement with the actual law, when the permeability coefficient is within the predicted range, the anti-seepage effect is optimal. (3) The difference of the water head and seepage gradient difference between the dam foundation and the grouting area near the curtain changes significantly with the grouting effect. Characteristics of seepage field in key parts of the dam foundation under the six curtain grouting coefficients, the water head value F1-F2 decreased by 75%, F3-F13 decreased by 28%, the seepage gradient value F1-F2 decreased by 88%, and F3-F13 decreased by 29%, namely the grouting effect of the dam foundation and the grouting area gradually weakens as the distance between the characteristic part and the curtain increases. The research in this paper can provide a theoretical reference for the analysis and evaluation of dam seepage conditions. [ABSTRACT FROM AUTHOR]

The effect of cement-grouting plays an important role in the engineering property of cement-treated sands. To investigate the effect of different water-cement (w/c) ratios on sand cementation, one dimensional seepage test was conducted with different particle size in this study. The permeability coefficient and uniaxial compressive (UC) strength of treated samples were studied respectively. Test results indicated that with the increase of w/c ratio, the increase of permeability coefficient of sands with particle size 1.25-2.50 mm is larger than that of sands with particle size 2.50- 5.00 mm after 7 days curing time. The UC strength of treated samples decreases with the increase of w/c ratio. The larger the particle size, the smaller the reduction of UC strength. These phenomena are closely related to the formed bond strength between sand particles. [ABSTRACT FROM AUTHOR]

Background: Understanding the pathophysiology of the blood brain–barrier (BBB) plays a critical role in diagnosis and treatment of disease conditions. Applying a sensitive and specific LC–MS/MS technique for the measurement of BBB integrity with high precision, we have recently introduced non-radioactive [13C12]sucrose as a superior marker substance. Comparison of permeability markers with different molecular weight, but otherwise similar physicochemical properties, can provide insights into the uptake mechanism at the BBB. Mannitol is a small hydrophilic, uncharged molecule that is half the size of sucrose. Previously only radioactive [3H]mannitol or [14C]mannitol has been used to measure BBB integrity. Methods: We developed a UPLC–MS/MS method for simultaneous analysis of stable isotope-labeled sucrose and mannitol. The in vivo BBB permeability of [13C6]mannitol and [13C12]sucrose was measured in mice, using [13C6]sucrose as a vascular marker to correct for brain intravascular content. Moreover, a Transwell model with induced pluripotent stem cell-derived brain endothelial cells was used to measure the permeability coefficient of sucrose and mannitol in vitro both under control and compromised (in the presence of IL-1β) conditions. Results: We found low permeability values for both mannitol and sucrose in vitro (permeability coefficients of 4.99 ± 0.152 × 10−7 and 3.12 ± 0.176 × 10−7 cm/s, respectively) and in vivo (PS products of 0.267 ± 0.021 and 0.126 ± 0.025 µl g−1 min−1, respectively). Further, the in vitro permeability of both markers substantially increased in the presence of IL-1β. Corrected brain concentrations (Cbr), obtained by washout vs. vascular marker correction, were not significantly different for either mannitol (0.071 ± 0.007 and 0.065 ± 0.009 percent injected dose per g) or sucrose (0.035 ± 0.003 and 0.037 ± 0.005 percent injected dose per g). These data also indicate that Cbr and PS product values of mannitol were about twice the corresponding values of sucrose. Conclusions: We established a highly sensitive, specific and reproducible approach to simultaneously measure the BBB permeability of two classical low molecular weight, hydrophilic markers in a stable isotope labeled format. This method is now available as a tool to quantify BBB permeability in vitro and in vivo in different disease models, as well as for monitoring treatment outcomes. [ABSTRACT FROM AUTHOR]

This study investigates the influence of clogging substances on pore characteristics and permeability of geotextile envelopes that were used for 3, 7 and 15 years in irrigated farmlands in Xinjiang region, which is arid and suffers from the soil salinity problem. Results show that the macropores (above 125 μm) of envelopes are evidently clogged, whereas the smaller pores less than 100 μm are still unblocked after operation. The permeability coefficients of geotextile envelopes after serving for 3 and 15 years are smaller than the minimum required permeability coefficients after clogging. The main chemical components of clogging substances in the geotextile envelope are silicon dioxide and calcium carbonate. Calcium carbonate content of the geotextile envelope is consistent with calcium carbonate content of soil. Chemical clogging susceptibility increases with the operation time of the subsurface drainage pipes. The ratio of O 90 size of envelope material over d 90 of soils (O 90 / d 90) and saturation index (SI) can be used to assess the susceptibility of physical and chemical clogging respectively. This study provides a preliminary reference for estimating the clogging susceptibility of geotextile envelopes in arid areas. [ABSTRACT FROM AUTHOR]

In order to study the consolidation-seepage coupling characteristics of silt soil in the front of dam under different loads, the consolidation-seepage coupling experiment of the silt soil samples where located in the front of dam from the depth of 10 cm, 50 cm and 100 cm was conducted respectively. The variation of void ratio and permeability in different consolidation stresses and the relationship between the void ratio and permeability coefficient with different depth silt soil samples were researched. The results show that the deformation of silt samples is gradually decreased with the depth increase under the same load. When the load reaches to 800 kPa, the compression deformation of silt sample at 10 cm depth is 5.32 mm, the deformation at 50 cm depth is 4.92 mm and the deformation at 100 cm depth is 4.54 mm. The void ratio of silt at different depths is gradually decreased with the load increase. The all e-lg p curves show a linear state and there is an obvious logarithmic relationship between the void ratio and consolidation pressure. The permeability coefficient of silt at different depths is decreased with the increase of consolidation pressure in initial stage, then decreased slowly in the later stage, showing obvious non-linearity. Moreover, the porosity is closely related to the permeability coefficient which is gradually decreased with the decrease of porosity. The relationship between permeability coefficient, consolidation pressure, pore ratio and permeability coefficient can be well expressed by using single exponential decay equation. [ABSTRACT FROM AUTHOR]

Black soil has strong swell-shrink characteristics due to the change of water content. Permeability and fractal behavior can be reflected by soil water characteristic curve (SWCC). Although many relevant models can calculate the SWCC, the applicability of these models on black soil is unclear. In addition, the prediction of the SWCC is complicated, as the necessary parameters are difficult and time-consuming to measure. In this context, a series of experiments on the SWCC of black soil was conducted in the laboratory. Based on the results and analysis, conclusions were drawn as follows: The pore fractal dimension is strongly correlated with dry density; that is, the larger the dry density is, the greater the fractal dimension becomes. The permeability coefficient decreases with the increasing of the matric suction. The three commonly SWCC models (Fredlund (1994), Van Genuchten (1980) and Gardner (1958)) are appropriate for predicting the SWCC of black soil. Moreover, the optimized van Genuchten model can improve the accuracy of prediction by replacing the model parameters with the formula of dry density. Compared with the van Genuchten model, the absolute value of relative error decreased from 4.50% to 3.75% after optimization. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) technology has been widely used for predicting permeability coefficients of porous medium, such as shales, sandstones, and coals. However, there have been limited studies on the prediction model of clay-quartz mixtures based on NMR technology. In this study, evaporation tests at 40 °C and NMR tests were simultaneously performed on eight clay-quartz mixtures with different mineral compositions. The results show that during the evaporation process, the decay rate of T2 total signal amplitudes was constant at first, and then decreased to 0 after a period of time. Based on the decay rate, the evaporation process was divided into two stages: the constant rate stage and the falling rate stage. Based on the two stages, the T2 cut-offs of eight mixtures were determined. The water in the mixture was divided into two parts by the T2 cut-off: the free water and the bound water. The prediction model of permeability coefficients of clay-quartz mixtures was established based on the Timur-Coates model. In order to simplify the process of predicting the permeability coefficient, fractal analysis was used to develop the relationship between the T2 cut-off and fractal dimension of the T2 spectrum of saturated mixture. A simplified method for predicting permeability coefficients of clay-quartz mixtures based on NMR technology without centrifugal and evaporation experiments was also proposed. [ABSTRACT FROM AUTHOR]

Porous Si 3 N 4 ceramics with controllable pore structures were prepared by polymethyl methacrylate (PMMA) as the pore agent combined with cold isostatic pressing (CIP) method. The pore structures of specimens were tailored via the changes in the content and particle size of PMMA. The higher the addition and particle size of PMMA, the larger the open porosity and pore size respectively. The increased Darcian and non-Darcian permeability coefficients are obtained as the open porosity and pore size of pore structures increase. The ratio of Darcian and non-Darcian permeability coefficient representing the individual contribution of viscous and inertial resistance during permeation process, that is strongly dependent on the pore size and open porosity, but there is distinct relationship for small and larger pores. Moreover, the comparison of the theoretical permeability coefficients with the experimental permeability constants of porous materials is presented in this work. [ABSTRACT FROM AUTHOR]

• Established exponential correlation between penetration coefficient and SMA porosity. • Investigated void distribution and permeation pathways within SMA course. • Validated non-uniform voids within SMA course via simulation and observation. This study investigates the water permeability characteristics of newly constructed Stone Mastic Asphalt (SMA) surface course, with a specific focus on the influence of connected voids arising from the compaction temperature during pavement construction. On-site evaluation of the permeability coefficient was performed, followed by core sample extraction from the same locations to investigate the correlation between the permeability coefficient and porosity. Industrial CT scanning was used to identify and separate void regions in the core samples. Three-dimensional digital reconstruction techniques were employed to analyze the morphology and spatial distribution of voids within the core. The connectivity of voids was assessed, providing insights into water infiltration pathways within the SMA course. Additionally, finite element simulation of the pavement temperature field was conducted to investigate the spatially differentiated distribution of voids within the SMA course. The findings reveal that approximately 38.3% of the voids are concentrated within a 1 cm depth below the top surface of the 4 cm-thick SMA course. The aggregation of voids enhances the likelihood of interconnection, facilitating water seepage. Water infiltrates through the open voids on the top surface and flows vertically and horizontally along the interconnected pathways. Notably, at a depth of approximately 2.5 cm, the flow transitions to horizontal spreading, aligning with the primary distribution interval of interconnected voids. The non-uniform distribution of voids is primarily influenced by the compaction temperature. The top and bottom portions exhibit higher void percentages, while the middle portion shows relatively fewer voids, consistent with the observed compaction temperature pattern. [ABSTRACT FROM AUTHOR]