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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 study the permeability characteristics of soft clay under vibration drainage conditions, vibration drainage consolidation instrument and variable head permeability test device were used to conduct permeability tests on soft clay under vibration drainage conditions, and the influence of load amplitude, frequency and void ratio on the permeability of soft clay was analyzed. The results show that the permeability coefficient of soft clay shows a trend of decreasing, then increasing and then decreasing with the increase of loading duration; the increase of permeability coefficient increases with the increase of loading amplitude; the increase of permeability coefficient at different frequencies is different in the middle of loading, and the highest increase is at 1 Hz; the e-k nonlinear expression is proposed for the vibration drainage condition, and the permeability coefficient decreases with the decrease of void ratio. The study can provide reference for the design and application of vibratory drainage consolidation method. [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]

The massive accumulation of graphite tailings causes serious environmental pollution, mainly from heavy metal pollution. Therefore, this article introduces a method of using graphite tailings as a high-content main material, cement as a small component of the auxiliary cementitious material, and clay as a substitute for cement. The compressive strength and permeability of graphite tailing–solidified material (GT, GT–Clay) were tested, and the effect of clay partially replacing cement as an auxiliary cementitious agent on GT–Clay performance was compared. In addition, inductively coupled plasma mass spectrometry (ICP) was used to analyze the effect of the graphite tailing placement time on the heavy metal content, as well as the changes in the GT heavy metal leaching concentration and its heavy metal content under outdoor freeze–thaw conditions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to elucidate the microstructural changes in the GT–Clay. The experimental results show that, as the substitution of clay for cement increased from 0 to 50%, the compressive strength of the 90% GT–Clay gradually decreased, and the permeability also increased. The compressive strength of 95% GT–Clay did not show significant changes, but the permeability increased, and when mixed with quicklime, gypsum, and silica fume, the permeability decreased. The Ni and As in graphite tailings fluctuated significantly with the placement time. The heavy metal leaching concentrations of the 90% GT and 95% GT were below the standard limit, and Cd, As, and Ni in GT were potential sources of pollution. The analysis of the microscopic test results showed that the hydration products of the GT–Clay included ettringite, Ca(OH)2, and calcium silicate hydrates. The hydration product stabilized and filled the gaps between the tailing particles, thereby cementing them together. Not only did it improve the mechanical strength of GT, it also reduced the permeability and heavy metal leaching rate. This study provides a new analytical approach to applying graphite tailings for environmental treatment. [ABSTRACT FROM AUTHOR]

In the practical operation of traditional landfills, compaction clay often experiences cracking, while the HDPE geomembrane may tear and bulge, resulting in a compromised performance of the landfill covering system. To address this issue, a capillary retarding covering material for landfill sites is proposed by utilizing municipal sludge and construction waste particles as substrates and incorporating a small quantity of calcium bentonite. The mechanical characteristics of the covering material were investigated using a standard consolidation test and a triaxial compression test. A permeability test and a soil water characteristic curve (SWCC) test were conducted to examine the permeability and capillary retarding effect of the covering material. Microscopic tests including SEM scanning, laser particle size analysis, and T2 NMR analysis were performed to investigate the connection mode, particle size composition, and pore structure characteristics of the covered particles. Based on the aforementioned research, the following conclusions can be drawn: The cohesion of the covering material ranged from 50 to 150 kPa, while the internal friction angle ranged from 24.23° to 31°. The cohesion was directly proportional to the content of construction waste, whereas the internal friction angle was inversely proportional to calcium bentonite content. The permeability coefficient ranged from 5.04 × 10−6 cm/s to 7.34 × 10−5 cm/s, indicating a certain level of impermeability. Both the sludge and the calcium bentonite contents jointly influenced the final permeability coefficient in a negative correlation manner, with a notable hydraulic hysteresis phenomenon observed. A higher content of construction waste leads to a more pronounced supporting force exerted by the formed skeleton structures within a load pressure range between 0 and 1600 kPa. When considering a mass ratio of municipal sludge: construction waste: calcium bentonite as 30:60:7, respectively, only a decrease in the pore ratio by approximately 13.20% was observed. This study provides valuable data support for designing and applying capillary retarding cover barrier systems in landfills. [ABSTRACT FROM AUTHOR]

The type of soil and its compactness significantly influence its permeability coefficient, which in turn affects the drainage difficulty of soil pore water and the distribution of the infiltration line. However, current tailings dam models typically consider only a single soil layer instead of taking into account the differences in soil types and compactness, resulting in a deviation between simulated results and actual conditions. To address this issue, this study proposes three models with a gradually increasing degree of layering refinement based on soil type and compactness. These models aim to simulate the variations in the infiltration line under three different strategies: constant head, rainfall, and drainage. The simulation results indicate that the average increase in the infiltration line of the three schemes after rainfall is 46.2%, 65.88%, 83.52%, respectively; the fitting percentages for each scheme of infiltration line after 720 days of drainage and the constant head stage are 72.38%, 88.27%, and 93.61%, respectively. It can be seen that the higher the refinement level of the layered model, the more sensitive it is to changes in the infiltration line. Furthermore, as the refinement level of the layered model increases, the simulation effect on the changes in the infiltration line improves, and the simulated results become more consistent with the actual situation. This finding provides a strategy and possibility for the study of the tailings dam's infiltration lines, safety, and stability. [ABSTRACT FROM AUTHOR]

In order to study the influence of heterogeneous field with permeability coefficient to the subsurface flow exchange, this study adopted a stochastic first-order analysis method to explore the cross-correlation between hyporheic exchange flux and permeability coefficient, as well as the spatial distribution of velocity variance. The results show that hyporheic exchange flux is positively correlated with permeability coefficient heterogeneity in every part of the streambeds with the high cross-correlation zone near the dunes surface. Ignoring the heterogeneity of the riverbed will lead to greater uncertainty of the flow velocity at the shallow position of the riverbed, in the field, the permeability coefficient of the shallow position of the riverbed should be monitored to reduce the uncertainty of the subsurface flow exchange. [ABSTRACT FROM AUTHOR]

The objective of this study is to formulate vegetated light porous concrete (VLPC) through the utilization of various cementing materials, the design of porosity, and the incorporation of mineral additives. Subsequently, the study aims to assess and analyze key properties, including the bulk density, permeability coefficient, mechanical characteristics, and alkalinity. The findings indicate a linear decrease in the volume weight of VLPC as the designed porosity increases. While higher design porosity elevates the permeability coefficient, the measured effective porosity closely aligns with the design values. The examined VLPC exhibits a peak compressive strength of 17.7 MPa and a maximum bending strength of 2.1 MPa after 28 days. Notably, an escalation in porosity corresponds to a decrease in both the compressive and the bending strength of VLPC. Introducing mineral additives, particularly silicon powder, is shown to be effective in enhancing the strength of VLPC. Furthermore, substituting slag sulfonate cement for ordinary cement significantly diminishes the alkalinity of VLPC, resulting in a pH below 8.5 at 28 days. Mineral additives also contribute to a reduction in the pH of concrete. Among them, silica fume, fly ash, fly ash + slag powder, and slag powder exhibit a progressively enhanced alkaline reduction effect. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing 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.)

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]

Compacted cement-bound soils (CCS) are widely used as leakage barriers around solid waste landfills and contaminated sites. However, a study of its long-term reliability in an acidic environment is relatively scarce. A 3-year-long experimental study on the changes in permeability coefficient and microstructure of CCS under acid attack was conducted, from which the following conclusions can be drawn: the permeability coefficient of CCS under weak acid (pH = 5.00) attack decreased progressively with time, from 4.90 × 10−8 cm/s at the beginning to 6.70 × 10−10 cm/s after 3 years. Under strongly acidic environments with pH values of 2.65 and 3.65, the permeability coefficients of CCS initially decreased and then increased with time, reaching 6.70 × 10−5 and 9.37 × 10−8 cm/s, respectively. The degradation effect of a weak acid (pH = 5.00) on the hydration products of cement was mild as a large amount of hydration products (e.g. C-S-H shaped in short fibrous) remained in the pores of CCS after 3 years of immersion. However, strong acid caused an obvious degradation effect on the hydration products, which almost disappeared after 3 years of immersion. Based on the study data, a unified mathematical model was developed to correlate the permeability coefficient of CCS, immersion time and acidic solution pH value. Furthermore, a quantitative expression function between the service life of CCS and solution pH value was established. [ABSTRACT FROM AUTHOR]

The potential impact of heavy metal ion infiltration on macroscopic and microscopic soil properties is a subject of academic interest. Laterite has an extensive distribution in southern China and is extensively utilized as a vertical containment wall for landfills. Consequently, there is a need to investigate how heavy metal ions affect laterite's microstructure and mechanical properties. To examine the impact of Cu2+ on laterite's microporous characteristics and mechanical properties, laboratory tests were conducted on the permeability, shear strength, microporous characteristics, and strong absorbed water content of Cu2+-contaminated laterite. The results show that Cu2+ hydrolysis generates an acidic environment, which leads to erosion of the cementing substance between the laterite particles, increasing the laterite's porosity and decreasing the soil's cohesive strength, thus affecting the shear strength and permeability of the laterite. When the concentration of Cu2+ is 5.0 g/L, the laterite demonstrated the most significant decrease in shear strength, 43.01%, while the permeability coefficient increased from 3.24 × 10−8 cm/s to 1.32 × 10−7 cm/s. Meanwhile, Cu2+ changes the content of strong absorbed water in laterite. The change of strong absorbed water content will affect the Van der Waals between laterite particles, promote the evolution of soil micropore structure, and lead to a decrease in the proportion of intra-aggregate pores (d < 1 μm) and an increase in the proportion of inter-aggregate pores (1 μm < d < 10 μm), which in turn affects the macroscopic shear strength and permeability. This study has improved our understanding of the mechanisms underlying the microporosity and mechanical property evolution of laterite when subjected to heavy metal attack. [ABSTRACT FROM AUTHOR]

Pervious concrete (PC) as a green infrastructure material has been increasingly used due to its positive environmental impacts, such as controlling storm water runoff, removing water pollutants and reducing heat island effect. The aggregate gradation is a critical factor influencing the physical properties of PC. Therefore, this paper represents an attempt to determine the effects of aggregate gradation on the various physical properties of PC, and then to explore relationships between them. To this end, three aggregate gradations 4.75–9.5 mm, 9.5–19 mm and 19–31.5 mm were recombined with various proportions (20–80%) to obtain five different gradations named as A, B, C, D and E. PC mixtures were prepared with these five aggregate gradations. Then, physical and mechanical properties of PC including porosity, permeability, compressive strength and water stability were investigated, according to the available specification. The results suggested that it was feasible to use waste concrete for permeable pavement, because all the specimens provided required specification requirements. Different linear relationships were also found between the maximum aggregate size and porosity, permeability coefficient, compressive strength and its loss rate. That is, porosity and permeability increased with the proportion of larger size aggregate increased, however, compressive strength reduced. Thus the compressive strength had an inverse correlation with the porosity and water permeability. Among five different aggregate gradations, group C (20% of 4.75–9.5 mm aggregate, 50% of 9.5–19 mm aggregate and 30% of 19–31.5 mm aggregate) can be seen as the optimum gradation and is suitable for base layer materials of permeable pavements. [ABSTRACT FROM AUTHOR]

Anisotropic permeability is of great significance for assessing the consolidation and drainage mode of soil layers in reclamation areas, as well as for preventing and controlling ground settlement after project construction. This paper analyzes the anisotropic permeability of the inland and nearshore soil layers in Chongming East Shoal, Shanghai, and the formation mechanism of anisotropic permeability through permeability and scanning electron microscope (SEM) tests. The results highlight that compared with dredger fill and sandy silt, the horizontal permeability coefficient of underlying soft clay (USC) is significantly higher than its vertical permeability coefficient, which is more significant in nearshore USC. Interestingly, the upper clay (21.5 m) in the thickest clay layer shows greater anisotropic permeability than the lower clay (41.5 m). Due to the instability of seepage channels, the USC anisotropic permeability increases in a fluctuating manner as the hydraulic gradient increases. Microstructural parameters are used to reveal the mechanism of anisotropic permeability, which shows that a simple soil skeleton and structure, strong particle orientation, decreased particle abundance, increased particle roundness, decreased particle contact area, and increased pore area all contribute to the enhancement of permeability. Moreover, micro-parameters have been proposed to evaluate anisotropic permeability in terms of the effective seepage-pore area. This approach addresses the constraint of water films on the permeability efficiency of USC particles. [ABSTRACT FROM AUTHOR]

During the operation of compressed air storage energy system, the rapid change of air pressure in a cavern will cause drastic changes in air density and permeability coefficient of sealing layer. To calculate and properly evaluate air tightness of polymer sealing caverns, the air-pressure-related air density and permeability must be considered. In this context, the high-pressure air penetration in the polymer sealing layer is studied in consideration of thermodynamic change of the cavern structure during the system operation. The air tightness model of compressed air storage energy caverns is then established. In the model, the permeability coefficient and air density of sealing layer vary with air pressure, and the effectiveness of the model is verified by field data in two test caverns. Finally, a compressed air storage energy cavern is taken as an example to understand the air tightness. The air leakage rate in the caverns is larger than that using air-pressure-independent permeability coefficient and air density, which is constant and small in the previous leakage rate calculation. Under the operating pressure of 4.5–10 MPa, the daily air leakage in the compressed air storage energy cavern of Yungang Mine with high polymer butyl rubber as the sealing material is 0.62%, which can meet the sealing requirements of compressed air storage energy caverns. The air tightness of the polymer sealing cavern is mainly affected by the cavern operating pressure, injected air temperature, cavern radius, and sealing layer thickness. The cavern air leakage rate will be decreased to reduce the cavern operating pressure the injection air temperature, or the cavern radius and sealing layer thickness will be increased.

Numerical simulation is an important method to determine the leaching range in the process of in-situ uranium mining, and the permeability coefficient is an important factor affecting the accurate calculation of leaching range by numerical simulation methods. However, the numerical model is difficult to completely describe the actual spatial distribution of permeability coefficients due to the complexity of the distribution of aquifer permeability. In order to analyze the influence of permeability coefficient uncertainty on leaching agent migration process and leaching range, according to the field condition test data of sandstone-type uranium deposits in Inner Mongolia, 200 random fields of permeability coefficient in accordance with the specific distribution were obtained using the Python geostatistical software package GSTools. All permeability coefficient random fields were applied to solute transport simulation, and Monte Carlo method was used to convert the parameter uncertainty of permeability coefficient into the uncertainty of model results. The results of simulation under homogeneous and heterogeneous permeability conditions were compared. The leaching agent in homogeneous conditions could not migrate outward and the leaching range is a regular circular shape. The direction of leaching agent migration is affected by the regional permeability between pumping and injection wells under heterogeneous conditions of permeability coefficients. When the permeability coefficient of the region between the pumping and injection wells is relatively higher, the leaching agent migrates only to the pumping wells and not outward. Conversely, a part of the leaching agent would spread along the preferential flow channels to the high-permeability region outside the pumping and injection wells region, resulting in a non-regular shape of contamination plume. Based on the analysis of the actual geological conditions, the complexity of its spatial distribution is ignored when the permeability coefficient is extended to the average value, and the influence of the random distribution of the permeability coefficient should be considered in the model. However, the leaching range obtained from different permeability coefficient random fields has obvious differences, indicating that the uncertainty of permeability coefficient leads to the uncertainty of simulation results, which can be quantified and analyzed using relevant statistical methods. The results of the quantitative analysis show that influence of permeability coefficient uncertainty on the expansion rate of the leaching range is distinct at different time. At the initial stage of the simulation (1-20 d), the influence of the uncertainty in permeability coefficient is low, and the leaching range expanded rapidly at an average rate of 350 m2/d. With the increasing of simulation time, the influence of permeability coefficient uncertainty is significant, and the expansion rate of leaching range is 18-54 m2/d. The expansion rate decreases but the uncertainty of leaching range shows a linear increasing trend. At the end of the simulation, the distribution characteristics of leaching range of 200 groups are counted, and it is found that the leaching range is concentrated in 20 000-30 000 m2 with a high degree of uncertainty. When the confidence levels are 95%, 85%, 75% and 65%, the confidence intervals of the leaching range are 34 072.0-17 699.8, 31 900.2-19 871.6, 30 688.9-21 082.8 and 29 770.1-22 001.7 m2, respectively. The higher the confidence level, the larger the confidence interval of the leaching range, indicating the higher uncertainty, and different confidence levels can be selected to determine the dissolved leaching range according to the demand in practical applications. The research results obtained by considering the uncertainty of permeability coefficients above are suitable for actual situation, therefore the results can provide reference for the determination of leaching range in uranium mining by in-situ leaching.

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.

Permeability characterized by permeability coefficient is one of the important engineering properties of clay, and its permeation mechanism depends on the permeation process of water in clay. To clarify the characteristics and influencing factors of the anisotropy of stress in red clay, indoor variable head permeability tests were conducted to obtain the permeability coefficients of undisturbed red clay in vertical and horizontal directions under different overlying loads. The research results indicate that under the same overburden load, the vertical permeability coefficient (kV) is greater than the horizontal permeability coefficient (kH), and on semi-logarithmic coordinates, both permeability coefficients exhibit a linear negative growth relationship with the overburden load. Moreover, with a gradual increase in the overburden load, the permeability coefficient ratio kV/kH shows a decreasing trend. When the overburden load does not exceed 150 kPa, the ratio of permeability coefficients (kV/kH) shows a linear decreasing trend, and when the overburden load exceeds 150 kPa, the rate of decrease gradually slows and eventually stabilizes. It is also found that the void ratio (e) is linearly related to lgkV and lgkH, and based on this, a prediction model for the anisotropy of stress in undisturbed red clay based on permeability coefficients is established. Under increasing osmotic pressure, the permeability coefficients in both directions exhibit linear growth. Essentially, it is the osmotic pressure that alters the stress pathways of red clay, and the smaller the overburden load, the greater the effect of osmotic pressure. With the increase in the overburden load, the anisotropy of stress gradually weakens.

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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]

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.)

In order to avoid subgrade diseases caused by groundwater erosion on highway, the organic silicon hydrophobic material was used as a new type of water resisting layer material to study the water barrier effect and the variation of its internal microstructure of soil, and the silty clay was the test object in this process. Firstly, the variation rules of soil permeability performance were studied through penetration test, and the action mode of hydrophobic material was summarized. Secondly, the contact angle test was used to characterize the hydrophobicity change of the soil surface. Finally the variation of the pore structure inside the soil was studied by means of image analysis. The results show that the permeability coefficient and the contact angle of the soil gradually decrease with the increase of the amount of the hydrophobic material per unit area. When the double-layer arrangement and the amount of the hydrophobic material is 100 g/m², the permeability coefficient is the lowest, which is 95.43% lower than that of the common soil. The contact angles of the soil modified with hydrophobic materials are all greater than 105°, the soil surface shows strong hydrophobicity. The hydrophobic material has an important influence on the microscopic pore structure of the soil. The transformation of large pores into small pores is an important reason for the enhancement of its impermeability. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of salt content and moisture content on the mechanical properties of loess-like saline soils, indoor triaxial tests were conducted by manually preparing loess-like saline soils with different salt contents, and the variation of shear strength parameters and permeability coefficients of loess-like saline soils under different salt content and moisture content conditions were analyzed. The results show that the shear strength parameters of saline soils show a trend of increasing and then decreasing with increasing salt content at low moisture content, and the lowest shear strength index is reached at 3. 2% of anhydrous sodium sulphate. Shear strength parameters of saline soils at high moisture content decreasing with increasing salt content. Under certain conditions of salt content, the shear strength parameters of saline soils all decrease with increasing water content, and the higher the salt content, the more obvious the change of shear strength index with water content. In addition, at a certain salt content, the permeability co-efficient of saline soils shows a clear tendency to increase as the water content increases; at a certain water content, the permeability coefficient of saline soils decreases with increasing salt content, and the higher the water content, the greater the change in permeability coefficient with salt content. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature 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.)

This study delves into the effects of sample height on consolidation behaviour, utilising the automatic air pressure consolidometer. Extensive tests were conducted on three varieties of dredged silt samples of varying heights from Qianwan, Shenzhen, China. The salient findings can be summarised as follows: (1) Compression curves for samples of different dimensions transitioned through three distinct phases: minimal load disturbance, elastic deformation, and plastic deformation. Notably, the void ratio during the latter two phases diminished as sample height increased. (2) A rising sample height corresponded to a reduced stable strain and compression index. Furthermore, the consolidation coefficient notably diminished with an escalation in the sample height, whereas the structural yield stress remained largely unaffected. (3) Given the disparate formation processes, stress histories, and material compositions between dredged and marine silts, the permeability coefficient of dredged silt was found to be superior to that of marine silt. Within the typical preloading pressure scope (50~300 kPa), the consolidation coefficient of dredged silt was lower compared to marine silt. However, as the consolidation pressure significantly surpassed this threshold, the coefficient disparity between the two silts narrowed. [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]

Porous asphalt concrete (PAC) has excellent performance in managing rainwater, improving groundwater quality, mitigating the heat island effect, and reducing traffic noise. However, PAC often becomes clogged with soil, sand, and other clogging materials, which attenuates its permeability performance. This paper investigated the anticlogging performance of PAC. Firstly, a clogging test of PAC was carried out, and the clogging material was aeolian sand. Then the PAC specimens were cleaned by manual brushing, vacuum pump suction, and high-pressure water cleaning after each clogging. The permeability coefficients (kR) after clogging and cleaning were measured by a variable head seepage device. Next, the influence of porosity, nominal maximum grain size and cleaning method on the permeability performance of PAC under cyclic clogging–cleaning were investigated in terms of the change law of the permeability coefficient. The effect of different clogging materials on the PAC's permeability performance also was investigated. The influence of PAC gradation parameters on the permeability performance of PAC pavement was investigated using statistical methods. The results showed that with the increase of loading times, the permeability coefficient's values after clogging and cleaning first decreased rapidly and then stabilized gradually. The larger the porosity and nominal maximum grain size, the better was the PAC's anti-clogging performance and the better was its effect on the permeability coefficient's recovery. The residual rate of permeability coefficient (γ) of PAC specimens with different porosities and nominal maximum grain sizes differed significantly. The value of γ was large for large-porosity and nominal maximum grain size PAC specimens after each cycle. The order of ranking of the cleaning effect from best to worst was high-pressure water cleaning, vacuum pump suction, and manual brushing. The order of ranking of the clogging effect was sandy soil mixture, aeolian sand, and silty soil. Among the PAC gradation parameters, the effect of porosity on PAC's anticlogging performance was greater than that of nominal maximum grain size. [ABSTRACT FROM AUTHOR]

Acrylic materials exhibit favorable grouting repair performance. However, their curing products are easily inclined to drying shrinkage, and their concrete impermeability repair characteristics have seldom been investigated. To improve material properties, reveal the impermeability repair mechanism, and address drying shrinkage, this study proposed the addition of styrene–acrylate copolymer emulsion (styrene–acrylic emulsion) to the grouting material to prepare two-component acrylate grouting materials. Using orthogonal and single-factor tests combined with physical and mechanical properties, the mechanical properties and impermeability repair performance (physical and mechanical properties combined) of grouting materials were analyzed and studied, and the optimal ratio of each component of acrylate grouting materials was determined. Results show that (1) the hydrogel produced by the reaction of sodium methacrylate with hydroxyethyl acrylate has good physical and mechanical properties. (2) With the increase in the accelerator dosage, the setting time of slurry initially decreases and then increases; as the initiator dosage increases, the setting time of slurry decreases, which is negatively correlated with the initiator dosage. (3) Talcum powder can improve the physical and chemical properties of gel and enhance the reliability and durability of acrylate grouting materials, and the comprehensive performance is the best at a dosage of 3%. (4) Styrene–acrylic emulsion can increase the solid content and reduce the volume drying shrinkage when added to grouting materials. The fractured impermeable specimens were repaired by grouting with prepared acrylate grouting materials and cured for 24 h for the impermeability test, and the water pressure for the 24 h impermeability repair was 1.0 MPa. This study's results provide important reference and basis for revealing the impermeability principle of acrylate grouting materials and evaluating their impermeability. [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]

In order to provide a new method for inhibiting the rise of capillary water, the influence of hydrophobic materials on the water-repellent performance of roadbed soils was investigated and the influence of hydrophobic substance dosage per unit area and action time on soil impermeability was analyzed. The results demonstrate that the permeability coefficient of the soil reduces dramatically as the amount of hydrophobic material per unit soil area increases, and start with an increment but later turned into a decrement with the action time. The permeability coefficient of the soil was 0.7892×10−7 cm/s as the minimum as with a drop of 98.86 percent under conditions of 125 g per unit area and an action time of 24 h. Furthermore, the organic silicone hydrophobic material will eventually form a dense hydrophobic film to block the infiltration of external water, thereby enhancing the hydrophobicity of the soil. [ABSTRACT FROM AUTHOR]

Water storage capacity has always been the core component of the underground water reservoir in open-pit coalmines. Taking the western underground water reservoir of Baorixile open-pit coalmine as the research background, boreholes in the waste dump overlying the underground water reservoir were designed and drilled, and the capacity characteristics of the underground water reservoir were studied by a layered summation method. These test results revealed that: (1) the regional strata from shallow to deep are the near-surface loose layer, upper bench loess, mixed stripping material, glutenite water reservoir layer and rubble collecting ditch; and the glutenite water reservoir layer is the main water storage body of the underground water reservoir. (2) Permeability coefficient, porosity, layered and cumulative water storage of the western underground water reservoir in Baorixile open-pit coalmine increase with the elevation increase, and show a quadratic function relationship. (3) The total storage capacity of the underground water reservoir is 1.2234 Mm3, and the average porosity is 0.1003, that is, each volume of the water storage medium can store 0.1003 volume of water. These results provide a scientific basis for the evaluation and determination of the water storage capacity of the underground water reservoir in open-pit coalmines. HIGHLIGHTS The design and construction of the underground reservoir in Baorixile open-pit coalmine.; A calculation method of underground reservoir capacity in open-pit coalmines based on a field borehole water injection test.; The reservoir capacity characteristics of the western underground reservoir of Baorixile open-pit coalmine.;

Abstract The spewing of a screw conveyor easily occurs from the earth pressure balance (called EPB) shield in a water‐rich sand stratum. This may lead to the collapse of the tunnel face and even serious subsidence of the ground surface. To understand the spewing mechanism of the shield screw conveyor and explore the critical hydraulic condition of soil spewing in a shield–soil chamber, a simplified theoretical model for the spewing of the screw conveyor was developed based on the equation of groundwater flow in the screw conveyor under turbulent state. Thus, coupling Darcy's law with Brinkman's equation, this model was implemented within the COMSOL Multiphysics framework. The underground water flow in the shield screw conveyor was simulated so as to obtain its velocity and flow rate. Numerical simulations show that the water pressure distribution is concentrated in the lower part of the soil chamber after the groundwater enters the soil chamber. When the groundwater enters the screw conveyor, its pressure gradually decreases along the direction of the screw conveyor. When the water flow reaches the stratum–shield interface, the flow velocity changes markedly: first increases and concentrates at the entrance of the lower soil chamber, plummets and stabilizes gradually, and increases again at the exit. The soil chamber and screw conveyor are significantly depressurized. It is also found that the soil permeability coefficient can be reduced to k

In order to study the subsidence deformation disaster prevention and mitigation in Fushun urban ground crack development area, we select different deformation sections of surface fault zone in Fushun West open-pit mine to carry out grouting reinforcement tests with sleeve valve tube method and full hole grouting method. Through the field practice, the rock mass is seriously broken and cavitated in the depth range of 18.50-25.5 m in the test area. F1A fault zone with full hole grouting method is better than sleeve valve tube method. It is better to use sleeve valve tube method in F41 fracture zone. Through the comparison of permeability and permeability coefficient before and after grouting, as well as drilling coring, it is shown that grouting reinforcement plays a filling and consolidation role in the test area, which is suitable for the treatment of deformation and failure of ground cracks.

In order to study the influence of different factors and the interaction of factors to the key performance of innovative recycled aggregate pervious concrete, by setting different levels of the three factors of the number of pipe holes, diameter and material type, response surface methodology was used to design experiment and establish positive and lateral compressive strength and response model of permeability coefficient, and experiment to verify the optimization results. The results show that the sensitivity degree of each factor to the impact of positive and lateral compressive strength is the number of pipe holes > the diameter of pipe holes > the elastic modulus of pipe holes. The sensitivity degree of the influence of various factors to the permeability coefficient is in the order of diameter of pipe holes > the number of pipe holes > the roughness of pipe holes. By comparing the model optimization prediction results with the validation test results, it is found that the experimental results are close to the model optimization prediction results, indicating that the design test based on response surface methodology has practical significance, and the theoretical analysis using response surface methodology can match the measured results of the performance of innovative recycled aggregate pervious concrete. [ABSTRACT FROM AUTHOR]

In this study, based on soybean urease and standard sand, the unconfined compressive strength test and permeability test of four variables of urease concentration, urea concentration, calcium chloride concentration and sodium alginate content under different combinations of values were carried out, and the range analysis and variance analysis of test data were carried out. On this basis, the coupling model of unconfined compressive strength and permeability coefficient of soybean urease reinforced sand was established based on four test variables. It was found that the engineering characteristics of soybean urease reinforced sand were significantly affected by the combination of variable values. The maximum value of unconfined compressive strength under the test combination condition was 6.5 times of the minimum value, and the minimum value of permeability coefficient was only 1/4 of the maximum value. The primary and secondary order of influence variables of unconfined compressive strength was: urea concentration > calcium chloride concentration > urease concentration > sodium alginate content, and the primary and secondary order of influence variables of permeability coefficient was: urea concentration > calcium chloride concentration > sodium alginate content > urease concentration. The influence of urea concentration on unconfined compressive strength and permeability coefficient was obvious, and the influence of the other three variables was not obvious. In addition, it was confirmed that the established coupling model of unconfined compressive strength and permeability coefficient of soybean urease reinforced sand had high correlation coefficient and significant linear regression, which can be used for subsequent research and engineering application. [ABSTRACT FROM AUTHOR]

The hydraulic conductivity is an important parameter in geotechnical studies. This parameter is required for analyzing, predicting, or modeling water flow, contamination movement and chemical transport in porous media of engineering constructions. Particle size distribution, is one of the most important factors affecting soil permeability. The main aim of the present research is assessing the effect of particle size distribution on the permeability coefficient of silty-sandy soils. For this purpose, three sandy soils and one silty soil from different regions of northern Iran have been selected and non-disturbed and disturbed samples have been provided from them. In the laboratory, the sandy soils were mixed with 10, 20, 30, and 40% of the silty soil, which is can be considered as an innovation for this research, and the physical properties were determined for all samples. To evaluate the permeability coefficient of the samples, first the suitable laboratory specimens were reconstructed with a relative density of 0.55 and then tested by a falling head permeameter apparatus. The obtained results indicated that the evaluated permeability coefficient is completely related to the particle size distribution indices of the soils, so that it increases linearly with increasing some indices namely D10, and D30 as well as decreases with increasing the other indices namely D50, D60, coefficient of uniformity (Cu), and Coefficient of curvature (Cc) as power functions. These found from six regression models developed between the parameters. The values of five calculated statistical indices were revealed that the developed models have high performance degree. [ABSTRACT FROM AUTHOR]

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.)

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology 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.)

Groundwater heat pumps (GWHP) are an efficient utilisation of shallow geothermal energy technology and of great significance in terms of promoting energy conservation and reducing emissions. However, recharge clogging has been a key problem restricting the continuous operation of GWHP. In this study, a simulation test device for sand column was designed with the aim of addressing chemical clogging induced by heat pump reinjection in a porous saline aquifer in the Huaibei Plain, China. The trend in the variation of the permeability coefficient was studied based on the detection of the sand sample composition, recharge water quality, and sand layer temperature, and the cause of formation was analysed using the saturation index (SI) and ion ratio method. The results indicated that the permeability coefficient in the sand column decreased exponentially, with a maximum and minimum decrease of 8.14% and 71.65% of the original coefficient, respectively, found in sections P2–P3 and P8–P9. Therefore, the clogging effect of the aquifer at approximately 200–400 mm from the recharge well was significant. Water–rock interactions predominantly involved the dissolution of halite, albite, chlorite, anhydrite, and dolomite and the precipitation of calcite, as well as the exchange adsorption of Ca2+ and Mg2+ to Na+, which were the key sources of ions during the water chemical evolution process. Finally, quartz was formed by the weathering and dissolution of aluminosilicate minerals such as albite, and particle migration and precipitation during the hydrodynamic disturbance were the primary causes of the front-end blockage of the column. [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]

High-strength pervious concrete (HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated, and a design method of HSPC pore characteristics (porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels, the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity (2.011%). HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology 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 Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department 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 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]

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.

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.

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 IS: 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 (IS = 1.00). The results presented in this study are important for assessing the use of waste coal ash for construction engineering purposes.

The deformation evolution of reservoir landslides of ten lags behind the variation in the reservoir water level during the operation of the Three Gorges Project, showing a deformation hysteresis effect, and the hysteresis effect is different with the difference in the permeability coefficient and fluctuation rate of reservoir water. Taking the Baijiabao landslide in the Three Gorges Reservoir area as an example, the variation law of the deformation lag time under different permeability coefficients k and reservoir water level decline rates v is studied by field investigation, monitoring data analysis and numerical simulation. The results show that when the permeability coefficient of the landslide is constant, the higher the decreasing rate of reservoir water level is, the more obvious the groundwater lag. When the reservoir water level drops at a certain rate, the greater the permeability coefficient of the sliding body is, the faster the groundwater drop.When the permeability coefficient of the sliding body is 0.85 m/d, the higher the rate of reservoir water level decline is, the shorter the deformation lag time of the landslide.The corresponding lag time is 3.74-9 d under different decline rates of the reservoir water level.When 0.47 < v/k < 1.18, 0.24 < relative deformation lag time < 1; when 1.18 < v/k < 2.38, 0 < relative deformation lag time < 0.24. When the reservoir water level decline rate is constant, the larger the landslide permeability coefficient is, the shorter the landslide deformation lag time is. Under different reservoir water level decline rates, the change rule of the relative deformation lag time with increasing v/k value is roughly the same, v=1.8 m/d, and the corresponding lag time of different permeability coefficients is 1.7-8 d. When 0.52 < v/k < 0.84, 0 < relative deformation lag time < 0.16; when 0.84 < v/k < 2.12, 0.16 < relative deformation lag time < 0.43; when 2.12 < v/k < 9, 0.43 < relative deformation lag time < 1. The research results have strong application value for the prediction and warning of reservoir landslides.