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Ceramic matrix composites (CMC) possess numerous distributed pore structures created during manufacturing, which can function as microchannels for fluid flow. This study examines the internal pores evolution process of C/SiC composites through in-situ X-ray computed tomography at varying temperatures. Visualize and analyze the three-dimensional geometric morphology and evolution behavior of composite materials at various temperatures through CT image reconstruction. Simultaneously, the pore network model was employed to model the microchannel structure of composite materials at different temperatures, extracting material pore characteristic parameters. The results suggest a close relationship between the mechanical properties of samples at different temperatures and their internal evolution behavior. The pore network model can identify the material's pore characteristic parameters and forecast the evolution trend of its permeability characteristics at varying temperatures. [ABSTRACT FROM AUTHOR]

Sandy clay is defined as a sand–clay mixture with the mechanical behavior dominated by fine clay but affected by coarse sand. Twenty sets of one-dimensional incremental load consolidation and falling head permeability coefficient tests were performed on sandy clays. The samples of sandy clays were prepared by mixing two hosted clays with different sand fractions from 0% to 60%. The interrelation between the change of permeability coefficient with void ratio and the compression curves is established. The results indicate that the effect of sand fractions on permeability coefficient can be attributed to the variation of void ratio at liquid limit induced by sand fractions. The initial void ratio affects permeability coefficient by changing the void ratio under the same effective vertical stress. These two findings highlight that the permeability coefficient-void ratio relationship of sandy clays is a function of void ratio at liquid limit and void ratio. An empirical method of estimating permeability coefficient is also proposed using two physical indices of void ratio and void ratio at liquid limit for sandy clays having void ratio at liquid limits ranging from 0.63 to 1.73 and initial void ratios varying from 0.72 to 2.67. [ABSTRACT FROM AUTHOR]

Sandy cobble soil has characteristics including a large internal friction angle, high permeability coefficient, and poor fluidity, which can result in serious tool wear, groundwater spilling, and transportation difficulties during shield construction. A subway in Luoyang is presented as an example case of shield construction. The optimal soil-water ratio of the bentonite slurry is 1:10 based on a sand and cobble stratum in the shield construction, and the optimal expansion duration is 18 h. Large-scale shear, slump degree, and permeability tests were conducted on a sodium-based bentonite slurry mixed with the sandy cobble soil. It was found that, with increasing slurry injection rate, the viscosity of the sandy cobble soil increased; the sand and stone separation phenomenon gradually vanished; the shear strength, internal friction angle, and permeability coefficient non-linearly decreased; and the slump degree non-linearly increased. The slurry injection rate necessary to meet the friction requirement of sandy cobble soil in the shield construction was 17%; the slurry injection rate necessary to meet the permeability requirement was 14%; and the slurry injection rate necessary to meet the fluidity requirement was 13% – 17%. The total thrust and cutter torque of the shield were found to be reduced by approximately 1/3, and the earth pressure balance maintained relatively well after the sandy cobble soil was mixed with the bentonite slurry, these points being remarkably significant to the high-speed advance of shield construction. This study is important with respect to solving issues concerning sandy cobble layers in subway shields. [ABSTRACT FROM AUTHOR]

With the intensification of global climate change, extreme rainfall events are occurring more frequently. Continuous rainfall causes the debris flow gully to collect a large amount of rainwater. Under the continuous increase in the water level, the water flow has enough power to carry plenty of loose solids, thus causing debris flow disasters. The intensity of the soil is reduced with the infiltration of rainwater, which is one of the key causes of the disaster. The rise in the water level affects the infiltration behavior. There have been few previous studies on infiltration under variable head. In order to understand the infiltration behavior of soils under the action of water level rises, this paper conducted an indoor permeability test on non-cohesive soil under the condition of an increasing water level. A numerical model was established using the finite element analysis software, Abaqus 6.14, and the pore pressure was increased intermittently to simulate the intermittent increase in the water level. Thereafter, the permeability coefficient and seepage length were changed to interpret the changes in the flow velocity and rate in the permeability test of the non-cohesive soil. The results showed that the finite element numerical simulation method could not reflect the particle movement process in the soil. The test could better reflect the through passage and void plugging phenomenon in soil; when the permeability coefficient alone changed, the velocity of the measuring point with higher velocity changed more violently with the permeability coefficient; when the length of soil seepage diameter was uniformly shortened, the velocity of water flow increased faster and faster. [ABSTRACT FROM AUTHOR]

Cement-based pervious concrete was prepared respectively with quartz powder, fine sand and silica fume as inorganic reinforcers. The influence of different inorganic reinforcers to the compressive strength, effective porosity and permeability coefficient of pervious concrete was investigated. The results show that the compressive strength of pervious concrete can be improved by adding certain amount of the inorganic reinforcing materials. In order to achieve the compressive strength of C25 and maintain good permeability, the content of quartz powder and fine sand should be 6% at least and 6%-8% of the total amount of coarse aggregate, and the content of silica fume should be 6%-10% of the total amount of cementitious material. Using the quadratic function equation, the permeability coefficient of pervious concrete can be obtained indirectly by measuring the effective porosity of pervious concrete. [ABSTRACT FROM AUTHOR]

In response to the challenges of poor engineering properties and the high difficulty in improving peat soil, a composite cement solidification agent (CCS) comprising ultra-fine cement (UFC) and ordinary Portland cement (OPC) was proposed for the solidification of simulated peat soil. The influence of UFC on the permeability of cement-soil samples was investigated through osmotic pressure tests and X-ray diffraction (XRD) experiments. Osmotic pressure tests results indicate that, under constant CCS dosage, the permeability coefficient k of specimens decreases with increasing UFC mass fraction, with a significant attenuation of the decreasing trend observed when the UFC mass fraction exceeds 12%. For CCS with a UFC mass fraction of 12%, k decreases with increasing CCS dosage, and the declining trend is notably attenuated when the dosage exceeds 25%. XRD results indicate that the diffraction peak intensity of calcium silicate hydrate (C-S-H) in the samples increases with both the increase in the UFC mass fraction and the curing time. Compared to OPC, CCS achieves superior solidification efficiency with a reduced cement dosage, facilitating the attainment of carbon reduction objectives. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation 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 Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology 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.)

Due to its unique geotechnical properties, loess presents itself as a cost-effective and energy-efficient material for engineering construction, aiding in cost reduction and environmental sustainability. However, to meet engineering specifications, loess often requires enhancement. Evaluating its permeability properties holds significant importance for employing improved loess for construction materials in landfills and artificial water bodies. This study investigates the influence of dry densities, grain size characteristics, grain size distribution, and admixture contents and types on the permeability of improved loess, focusing on the Malan and Lishi loess. The falling head permeability test was conducted to analyze how each factor affects the permeability of the improved loess. The findings indicate that the permeability coefficient decreases with increased dry density and admixture content. Conversely, it demonstrates a linear increase with the average grain size (d50), restricted grain size (d60), and the product of the coefficient of uniformity and coefficient of curvature (Cu × Cc). The primary influencing factor is the type of admixture, followed by Cc and d60. Furthermore, this study developed a predictive model for permeability using a support vector machine (SVM), surpassing the predictive accuracy of linear regression and neural network models. The model provides a robust prediction for the permeability of superior loess material. [ABSTRACT FROM AUTHOR]

Recently, some travertine landscape groups in Huanglong Scenic Spot have been degraded to varying degrees. Surface water leakage, blackening and desertification have occurred on a large scale in the dense distribution area of Salix cupularis shrub, which has adversely affected the core value of the Huanglong World Natural Heritage Site. The relationship between shrub expansion and leakage enhancement has not been fully understood. In this study, travertine pool group of typical shrub area was selected in the north of Yingyue Pool in the upper reaches of Huanglong, and 4 shrub cover levels were set: no shrub (coverage 60%). In-situ infiltration test was conducted to determine the leakage intensity and to evaluate the changes of travertine pore structure and permeability parameters in shrub area. With the comparison of the leakage intensities in different shrub cover level areas, the mechanism of surface water leakage of travertine under the influence of Salix cupularis scrub is summarized. The results show that (1) the leakage intensity increases with the increase of coverage. When the coverage of Salix cupularis shrub exceeds 60%, the leakage intensity changes significantly, which should be related to the rapid diversion of large pores. (2) Under the influence of algae activities and decomposition of plant residues, new travertine with more pores and holes is formed in the scrub area, resulting in higher natural leakage intensity than that in the non-scrub area. (3) The root activities of Salix cupularis shrub changes the primary travertine structure, leading to loose primary travertine and increases of pore diameter, effective porosity, and permeability coefficient. The enhanced groundwater seepage resulted in enhanced overall surface water leakage in the travertine pool. (4) The transformation of travertine pore structure by Salix cupularis roots is depended on the root cleavage. The dissolution of travertine cement by root solution leads travertine to uniform loose accumulation. The results show that the root and algal activities in Salix cupularis scrub area mainly control the process of surface water leakage enhancement. This study have basic value for the evolution analysis and conservation of Huanglong travertine natural heritage landscape.

The timely repair of high-density polyethylene (HDPE) membrane leakage in landfills is an important means of environmental risk control, which is critical for preventing leachate from polluting groundwater and soil. Electric repair technology is expected to become a hot spot in the leakage repair of HDPE films, because it can solve the issues of complex operation, high costs, and security risks during the operation and closure of landfills. To explore the influence law of various technical factors on the electric repair process, we carried out single factor experiments on the main influencing factors such as the operation time, bentonite concentration and dispersant/bentonite dosage ratio, leakage size, and calcium concentration. We then explored the best technological conditions. The results showed that accumulation at the leakage site possessed a good repair effect with a permeability coefficient of 4.22 × 10−6 cm/s. Furthermore, we observed that the Zeta potential played an important role in the electric repair technology, where the higher the absolute value of the Zeta potential, the faster the electrophoretic migration rate of the bentonite particles, and the lower the permeability coefficient of accumulation. This study may serve as a theoretical basis and offer scientific guidance for the directional electric repair of HDPE membrane leakage during the operating period and after the closure of landfills.

Ion-adsorption rare earth (RE) ore is a typical kind of rare earth ore derived from the weathering crust of igneous rocks. Variation in permeability of ion-adsorption rare earth ore is one of the indicative factors of mining efficiency. Permeability of the RE ore is controlled by its pore structure. Previous studies mainly kept on the RE ores in completely weathered zones, little on those in the zones with other weathering degrees. With the exhaustion of rare earth resources in the completely weathered zone, the extraction of the RE ore from the zones with other weathering degrees has gained more attention from the industrial sectors. This study shows a study on variations in pore structures and permeabilities of the RE ores in the zones with different weathering degrees, including the residual soil and completely weathered and highly weathered zones. The undisturbed samples were taken from an un-mining section of the Zudong mining area in Jiangxi province. Simulated in situ leaching experiments were conducted on the samples to measure their permeability coefficients before and after leaching. X-ray computer tomography scanning techniques were applied to the capture structure of the samples before and after leaching, and image processing techniques were used to construct their three-dimensional pore structure and extract their pore structure parameters. Variations in pore structure parameters and permeability coefficients of the RE ores from the zones with different weathering degrees were then carried out by a quantitatively comparative analysis. The results indicate that (1) the variation rate in permeability coefficient, and the pore structure parameters, including porosity, connectivity, and average coordination number, decrease with the decrease in weathering degree. Notably, these variation rates for the RE ores in the highly weathered zone are the smallest, indicating the RE ores in this zone are more leachable than those in residual soil if their abundance is not much different. (2) The mechanism leading to their differences was further investigated by the analyses of particle size distribution and mineralogical composition before and after leaching. The analysis results indicate that the differences in their variation of pore structure and permeability among the RE ore in the zones with different weathering degrees are caused by the differences in followings during leaching, including the chemical decomposition of plagioclase and mica, ion exchange, and disaggregation.The results can provide reference for the full development and utilization of similar ion-adsorption rare earth ore.

To study the nonlinear permeability characteristics of silted soil in front of dams in the southern mountainous areas of Ningxia, taking the technique of “raising earth-dam from upstream deposited mud” for the reservoirs eliminating danger and reinforcement in loess hilly areas of southern Ningxia as the project background, the consolidation and permeability test was conducted to determine the vertical deformation and permeability coefficient of undisturbed silted soil at depths of 50, 100, and 150 cm under pressures of 25, 50, 100, 200, 400, 800 kPa. Based on the correlation between the permeability coefficient and pore ratio, a double logarithmic nonlinear seepage model was proposed by using pearson correlation and grey correlation analysis, which was suitable for the silted soil in front of earth-dam in this area. Results show that the pearson correlation coefficient and the grey correlation coefficient of pore ratio under 400 kPa consolidation pressure are 0.968 and 0.893, respectively, thus indicating a more significant association between them. Moreover, they surpass the correlation coefficients of other forms of pore ratios. The determination coefficient R² of the fitted seepage model is above 0.93. It not only better reflects the permeability characteristics of silt in front of dam in the southern mountainous area of Ningxia, but also makes up for the shortcomings of insufficient prediction accuracy and complex parameters of the single exponential seepage model. This quantitative model of consolidation-permeability coefficient can provide relative references for the study on large deformation nonlinear drainage consolidation of the silted soil in front of earth-dam. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology 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.)

The permeability coefficient of landslide mass, a key parameter in the study of reservoir landslides, is commonly obtained through in situ and laboratory tests; however, the tests are costly and subject to high variability, leading to potential biases. In this paper, a new method was proposed to inversely estimate the permeability coefficient of landslide layers using monitoring data of groundwater level (GWL). First, the landslide transient seepage simulation was conducted to generate sample data for permeability coefficients and GWL during a reservoir operation cycle. Second, using GWL data as input and permeability coefficient data as output, the least-square support vector machine (LSSVM) was trained with two optimization algorithms, the particle swarm optimization (PSO) algorithm and the whale optimization algorithm (WOA), to construct the nonlinear mapping relationship between simulated GWL and permeability coefficients. Third, the accurate permeability coefficients for landslide seepage simulation were inverted or predicted based on the monitored GWL. Finally, using the inverted permeability coefficients for landslide seepage simulation, we compared simulation results with actual monitored GWL and achieved good consistency. In addition, this paper compared the inversion effects of three different algorithms: the standard LSSVM, PSO-LSSVM, and WOA-LSSVM. This study showed that these three algorithms had good nonlinear fitting effects in studying landslide seepage fields. Among them, using the inversion values from PSO-LSSVM for landslide seepage simulation resulted in the smallest relative error compared to actual monitoring data. Within a single reservoir operation cycle, the simulated water level changes were also largely consistent with the monitored water level changes. The results could provide a reference to determine landslide permeability coefficients and seepage. [ABSTRACT FROM AUTHOR]

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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]

In order to explore the influence of vegetation root content on the water holding and permeability characteristics of expansive soil, samples with different root content were prepared by mixing bermudagrass roots with expansive soil from Nanning expansive soil area, and indoor pressure plate test and variable head permeability test were conducted, the Van Genuchten-Mualem model was used to predict the unsaturated permeability coefficient of expansive soil with different root contents. The results show that the water holding capacity of expansive soil decreases after the addition of roots, and the addition of roots increases the proportion of large and medium pores in the expansive soil. The higher the root content, the greater the proportion of large pore volume to total pore volume, and the greater the decrease in water holding capacity compared to pure soil. In saturated state, the permeability coefficient of expansive soil increases with the increase of root content. In unsaturated state, the permeability of expansive soil at low suction stage (0 ~ 25 kPa) increases with the increase of root content. As the matrix suction increases to high suction stage (200 ~ 1 000 kPa), the effect of root dominant flow decreases, and the permeability of expansive soil with roots gradually tends to be lower than that of pure soil. The mesoscopic results indicate that the incorporation of root system causes through cracks in the expansive soil, which is a key factor affecting the water holding and permeability of the expansive soil. This study further reveals the mechanism and regularity of the infiltration enhancement effect of vegetation roots on expansive soil, providing a reference for comprehensive evaluation of the effect of vegetation protection on expansive soil slopes. [ABSTRACT FROM AUTHOR]

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To systematically investigate the factors affecting the performance of permeable concrete on road surfaces, blocks with different porosity, particle sizes, water-to-cement ratios, and cement-to-aggregate ratios were prepared. Additionally, varying amounts of admixtures were added to some blocks to explore the influence of the admixture types and content on the performance of permeable concrete. The results indicate that the larger the particle size of the aggregate used in the block preparation, the higher the permeability coefficient of the blocks and the lower the compressive strength. The water-to-cement ratio affects the strength of the cement matrix, resulting in variations in the block strength. A higher cement-to-aggregate ratio leads to a lower porosity in the permeable concrete, a higher cement matrix content, a reduced permeability coefficient, and an increased compressive strength of the blocks.

This is an article in the field of ceramics and composites. In order to improve the impermeability and microstructure of the impermeable wall materials, four kinds of calcium-based bentonite modified and filling material with different dosages were prepared under the action of alkali excitation reaction. The modified and filling material samples in the curing process were tested by flexible wall penetration (FWPT), nuclear magnetic resonance (NMR) scanning and electron microscope scanning (SEM). The results show that the permeability coefficient of filling material samples decreases first and then increases with the increase of bentonite content, and reaches a minimum value when the content of bentonite is 4%. The relaxation time (T2) distribution curves of the filled material specimens after curing from 1 to 28 d were all bimodal, with more than 80% of the peaks representing small pores, and the percentage of the peaks representing large pores decreasing with the increase of curing time. According to SEM images, it can be seen that a certain amount of calcium bentonite can promote the occurrence of hydration reaction, and the porosity of the material is significantly reduced. At 4% phosphate slag, the cementitious filler has the best compactness and better impermeability and strength. Accordingly, it can be determined that the better dosage of phosphate slag modified cementitious filler is 4%.

Earth dams, essential hydraulic structures that form the link between water management and power generation, require careful examination of their structural and functional integrity. The essence of its stability lies in the dynamic response of soil structures used in construction to diverse operational stresses. To address this problem, it is necessary to conduct a comprehensive analysis of various geometric and hydraulic factors. This study focuses on unraveling the complex dynamics governing the slope stability (D/S) of the proposed earth dam section. Pivotal indicators for this evaluation are the frictional and shear strength of the soil, which responds to the countless stresses encountered during the operation phases. Taking advantage of advanced Geostudio software, we examined the effect of different filter lengths, permeability coefficients, and operating heads on shear strength and friction. The findings highlight a consistent pattern in the behavior of both frictional and shear forces with respect to distance from the base of the dam. These strengths rise to peak values at a specific distance (65 m), after which a downward trend is observed towards the toe of the dam. Notably, the study emphasizes the critical role of the 30 m filter length, the permeability coefficient K3, and to some extent, K2, in amplifying the friction force values at storage levels ranging from 15 to 40. moreover, the peak friction force at 138.2 kPa and the maximum shear strength value at 158.2 kPa appear at an operating head (H) of 40 m. This optimal performance is intricately linked to the strategic use of a 30 m filter length and a permeability coefficient of m/s. However, this research not only highlights the delicate interplay between hydraulic and geometric factors within the stability of earth dams but also underscores the critical importance of specific configurations in fortifying against potential failure. The insights gained from this study contribute significantly to considerations related to the design, construction, and operation of earth dams, ensuring robust performance in the face of diverse challenges.

Mud plays an important role in foundation treatment, mud-water shield and other projects, and the thickener is the key to the quality of mud. The thickening agent used in traditional mud is mainly sodium carboxymethyl cellulose (CMC), which is difficult to degrade and easily pollutes the environment. To address the above problems, guar gum and xanthan gum were used to replace the traditional mud additives for green mud configuration. The optimal ratio of the mud and the permeability characteristics of its new mud skin were studied through proportioning experiments and improved filtration loss experiments. The results show that the optimal ratio of guar gum to xanthan gum is 1∶ 5, and the permeability coefficient of the mud skin can be effectively reduced by increasing the test pressure. The effect of CMC and the new additives on the mud modification is roughly the same, and the permeability coefficient of the mud skin obtained with the addition of 2. 5 g of guar gum to the bentonite clay and 0. 5 g of xanthan gum is three orders of magnitude smaller than that of the same quality fraction of the pure bentonite clay slurry. The modification effect of the new natural additives on the mud is better, and the addition of polymer materials will make the thickness of the mud skin formed smaller. The results of the test and theoretical analysis prove the feasibility of the new green mud in the application of pile foundation engineering, which can be widely used. [ABSTRACT FROM AUTHOR]

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Unsteady filtration of a Bingham non-Newtonian fluid to a horizontal well is considered. The experimental results show that when such liquids flow in porous media at low pressure gradients, deviations from the linear Darcy law appear. A feature of the movement of Bingham non-Newtonian fluids in a porous medium is the fact that filtration becomes noticeable only after the pressure gradient reaches a certain critical value—the limiting pressure gradient. The formulation of the inverse coefficient problem for determining filtration parameters during the flow of Bingham non-Newtonian fluid to a horizontal well is given. Pressure change curves measured at the well are used as initial information. To numerically solve the inverse coefficient problem, a computational algorithm based on regularization methods is proposed. [ABSTRACT FROM AUTHOR]

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Granite residual soil has distinctive engineering characteristics due to its unique properties, and the resulting slopes are less stable and less resistant to rain erosion. The granite residual soil was improved by the addition of 5%, 10%, 15% and 20% fly ash, and the effects of fly ash on the intensity index and penetration of granite residual soil were investigated by triaxial strength tests and permeability tests. In combination with scanning electron microscopy measurements, a study of the stability of fly ash-modified granite residual soil slopes by modeling rainfall using the finite element software ABAQUS revealed the following: (1) the permeability coefficients of the residual granitic soils decreased by one order of magnitude when fly ash was added; (2) the improvement in the triaxial strength index of the improved soil was most pronounced when the dosage of fly ash was 15%, so that a dosage of 15% was considered optimal; and (3) numerical simulations concluded that the stability of the slope formed by 15% fly ash-improved soil fill improved significantly relative to the original slope, with the coefficient of safety increasing from 1.06 to 1.42, and the resistance to water seepage also significantly improved. [ABSTRACT FROM AUTHOR]

In the exploration of sustainable construction materials, the application of ferronickel slag (FNS) in creating pervious concrete has been investigated, considering its potential to meet the dual requirements of mechanical strength and fluid permeability. To elucidate the statistical properties and models for predicting the performance of FNS-composited pervious concrete with different sizes of aggregates and mixtures, a series of experiments, including 54 kinds of mixtures and three kinds of aggregate, were conducted. The focus was on measuring the compressive strength and the permeability coefficient. The results indicate that the compressive strength of pervious concrete decreases with the increase in aggregate size, while the permeability coefficient increases with the increase in aggregate size. Through normalization, the variability of these properties was quantitatively analyzed, revealing coefficients of variation for the concrete's overall compressive strength and the permeability coefficient at 0.166, 0.132, and 0.150, respectively. Predictive models were developed using machine learning techniques, such as Linear Regression, Support Vector Machines, Regression Trees, and Gaussian Process Regression. These models demonstrated proficiency in forecasting the concrete's compressive strength and permeability coefficient. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology 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.)

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]

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. [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]

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 characterization 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. [ABSTRACT FROM AUTHOR]

Porous concrete (PC) is considered a promising paving material due to its eco-friendly and multi-functional characteristics. Compressive strength and coefficient of permeability are two key performance parameters of PC, but limited research has been conducted so far on their mutual relationship. In this paper, PC with three target porosities (15%, 20% and 25%) were prepared and 10 water–cement ratios between 0.2 and 0.4 were designed for each target porosity. After the samples were cured, the porosity and permeability coefficients were tested, followed by the compressive strength test. The porosity, permeability coefficient, and compressive strength characteristics of PC and their interrelationships were analyzed based on the test results. Moreover, a mathematical model is developed to characterize the relationship between compressive strength and permeability coefficient by analyzing empirical results and theoretical derivations. The results show that the effective porosity approaches the target porosity when the water–binder ratio (w/b) is in the range of 0.26–0.34. The strength and permeability of the PC can be both maintained at a high level when the effective porosity is in the range of 18–21%. Specifically, the PC may lose its water permeability by sealing the bottom with a w/b of 0.4 or more. Moreover, a new empirical model for the compressive strength and permeability coefficient of PC is established based on Griffith’s fracture theory. The model proposed presents a better agreement with the experimental data and could provide a better prediction of the compressive strength of PC by selecting the appropriate parameters. This research enriches the performance prediction model of PC and provides a basis and reference for PC material design and objective optimization. [ABSTRACT FROM AUTHOR]

Copyright of Earthquake (1000-3274) is the property of Editorial Office of Earthquake Journal 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.)

The aim of this research was to measure the filtration properties of waste coal ash under the influence of hydrostatic pressure generated in a three-axial compression apparatus. The scope of work included determining the compactibility parameters, maximum bulk density and optimal moisture content. Permeability tests were performed for a sample with an average grain composition at three compaction indices I S : 0.964, 0.98 and 1.00. The hydrostatic pressure ranging from 0.5 to 1.8 bar corresponded to the layer depths from 2.17 to 7.83 m. Gradually increasing the pressure during the first loading cycle caused irreversible changes in the structure of the sample by local material agglomeration or grain interlocking. The water permeability coefficient was higher in the second loading cycle than in the first cycle. It was shown that waste coal ash cannot be used as a construction material on its own. To obtain constant filtration properties, the waste coal ash material should be doped, or an optimal compactionshould be used ( I S = 1.00). The results presented in this study are important for assessing the use of waste coal ash for construction engineering purposes. [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]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials 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 Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources 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.)

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]

Copyright of Railway Construction Technology is the property of Railway Construction Technology 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.)

In order to save the consumption of natural high quality aggregate and improve the utilization rate of nano-composite materials, the investigation on the compressive strength and water permeability of nano-composite modified reclaimed aggregate concrete materials was proposed. In this experiment, reclaimed nano-ceramic aggregate was used to replace natural aggregate, and the effects of reclaimed aggregate substitution rate, water-cement ratio and target porosity on the compressive strength and permeability coefficient of reclaimed ceramic aggregate pervious concrete were studied. The reclaimed ceramic aggregate was pretreated with modifier. The results show that with the increase of substitution rate, the compressive strength decreases and the permeability coefficient has little difference. With the increase of water-cement ratio, the compressive strength increases first and then decreases, and the water permeability coefficient has little difference, but the value is lower when the water-cement ratio is greater than 0.4. As the target pore increases, the compressive strength decreases and the permeability coefficient increases. The optimal test scheme is as follows: the replacement rate is 40 %, the water-cement ratio is 0.35, and the porosity is 15 %. In this case, the performance of the specimen is better. Conclusion: With the increase of replacement rate, the performance index of recycled aggregate decreases, the compressive strength of pervious concrete decreases continuously, and the permeability coefficient has little difference. With the continuous increase of water-cement ratio, the compressive strength increases first and then decreases, which can meet the construction requirements.

The evaluation of grouting effect is one of the crucial links in grouting water control project. As grouting technology matures, traditional methods of evaluating grouting effects are more subjective and fewer objective, which leads to the drawback that the evaluation results deviate from reality. Taking the grouting project of 8901 working face in Baizhuang Coal Mine of Shandong Province as the background, combining existing research and field experience, the grouting final pressure, permeability coefficient, water absorption rate and the number of dry material per ton of water are selected as the evaluation indexes, and the comprehensive evaluation system of grouting effect is established. Based on the comprehensive evaluation theory, a comprehensive subjective and objective weighting method is proposed, which based on analytic hierarchy process(AHP) combined with CRITIC objective weighting method. And the objectivity ofpf indicator assignment is improved by combining subjective and objective weights. Based on the combination weighting method, a comprehensive evaluation model of grouting effect is established, which is sorted by technique for order preference by similarity to an ideal solution (TOPSIS) and assisted by rank sum ratio (RSR). The evaluation results are converted into visual partition maps and compared with the actual evaluation results of field engineering and the results of the testing process after grouting, and the results show that the model has superior accuracy and rationality.