摘要：
Marine soft clay is characterized by a high water content and low strength, exhibiting pronounced creep deformation under long-term loading that threatens the serviceability and durability of coastal infrastructure. Accordingly, this study develops a creep constitutive model that combines elastic, plastic, and viscous effects and quantitatively evaluates time-dependent deformation under varying water contents and stress levels to provide reliable prediction tools for tunnel, excavation, and pile-foundation design. Cyclic creep tests were carried out on reconstituted marine soft clay with water contents of 40–60% and stress ratios of 0.4–1.2 using a pneumatic, fully digital, closed-loop triaxial apparatus. A “nonlinear spring–Bingham slider–dual viscous dashpot in parallel with a standard Kelvin dashpot” element assembly was proposed, and the complete stress–strain relationship was derived. Experimental data were fitted with Python to generate a creep-strain polynomial and verify the model accuracy. The predicted–measured creep difference remained within 10%, and the surface-fit coefficient of determination reached R2 = 0.97, enabling rapid estimation of deformation for the given stress and time conditions. The findings offer an effective method for the precise long-term settlement prediction of marine soft clay and significantly enhance the reliability of the deformation assessments in coastal civil-engineering projects.
摘要：
Rapid urban industrialization has significantly increased the generation of industrial solid waste, posing substantial challenges for its effective and sustainable disposal. This study utilizes industrial waste combined with construction waste (CW) to solidify dredged sediment (DS), resulting in the creation of a novel solid waste-based landfill cover material (GH). After 20 dry-wet cycles, GH retained favorable mechanical performance, with compressive strength ranging from 4.31 to 6.83 MPa, volumetric shrinkage between 1.56% and 2.96%, and a stabilized permeability coefficient of 8.74 x 10- 8-1.412 x 10- 7 cm/s. Furthermore, the GH material functions as an impermeable layer within landfill cover systems, which were evaluated through a field-scale model test. The cover system at a depth of 40-60 cm exhibited the most substantial recharge from rainfall, with volumetric water contents were 17.97-51.19%. The GH at the bottom of the model box did not achieve saturation at any point during the experiment. A comprehensive characterization of the GH was conducted using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The solidification mechanisms of industrial solid waste and municipal construction waste in lake sediment were elucidated. This study pioneers the solidification of lake sediment using industrial and construction waste to develop a solid waste-based landfill cover material, addressing both waste management and environmental sustainability. By converting harmful waste into a durable, low-permeability material, this research presents a sustainable strategy for mitigating landfill pollution and reducing carbon emissions. This approach not only promotes waste recycling but also improves the mechanical and environmental performance of landfill covers, representing a notable advancement in sustainable geotechnical engineering.
摘要：
Solid waste-based cementitious materials represent a promising alternative to conventional Portland cement, contributing to a reduction in carbon dioxide emissions and enhancing the recycling of industrial and municipal waste. However, these materials are susceptible to harsh environmental conditions, such as sulphate attack, which may result in expansion, strength degradation, and alterations in permeability. This study systematically investigated the effects of sulphate exposure on the mechanical properties and permeability of cementitious materials derived from industrial and municipal solid wastes, such as blast furnace slag, desulphurisation gypsum, construction waste, and municipal sludge. Microstructural and chemical characterisation was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). In sulphate solutions ranging from 0.2 to 50 g/L, the unconfined compressive strength of these materials increased by 5.8% to 24.8% during the initial 10 days of exposure, before decreasing to 4.13–9.18 MPa after 90 days. Sulphate reactions with industrial waste components resulted in the formation of expansive phases, such as ettringite and gypsum dihydrate, leading to structural degradation. The particle size of construction waste and the slag content significantly influenced the rate of sulphate-induced degradation.
Solid waste-based cementitious materials represent a promising alternative to conventional Portland cement, contributing to a reduction in carbon dioxide emissions and enhancing the recycling of industrial and municipal waste. However, these materials are susceptible to harsh environmental conditions, such as sulphate attack, which may result in expansion, strength degradation, and alterations in permeability. This study systematically investigated the effects of sulphate exposure on the mechanical properties and permeability of cementitious materials derived from industrial and municipal solid wastes, such as blast furnace slag, desulphurisation gypsum, construction waste, and municipal sludge. Microstructural and chemical characterisation was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). In sulphate solutions ranging from 0.2 to 50 g/L, the unconfined compressive strength of these materials increased by 5.8% to 24.8% during the initial 10 days of exposure, before decreasing to 4.13–9.18 MPa after 90 days. Sulphate reactions with industrial waste components resulted in the formation of expansive phases, such as ettringite and gypsum dihydrate, leading to structural degradation. The particle size of construction waste and the slag content significantly influenced the rate of sulphate-induced degradation.
期刊：
Construction and Building Materials,2025年488:142158 ISSN：0950-0618
通讯作者：
Lan, JR
作者机构：
[Zou, Nachuan; Lu, Haijun; Dong, Yiqie; Zang, Meng] Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Peoples R China.;[Lan, Jirong] Hong Kong Polytech Univ, Civil & Environm Engn, Hong Kong, Peoples R China.;[Huang, Bo-Tao] Zhejiang Univ, Inst Adv Engn Struct, Hangzhou, Peoples R China.
通讯机构：
[Lan, JR ] H;Hong Kong Polytech Univ, Civil & Environm Engn, Hong Kong, Peoples R China.
关键词：
Phosphogypsum;Grinding kinetics;Fractal theory;Activity index
摘要：
Mechanical ball milling significantly enhances the recovery rate and utilization efficiency of phosphogypsum (PPG). This study investigates the mechanical activation of PPG. Mechanical ball milling was conducted at a speed of 300 r/s for periods ranging from 30 to 120 min. The particle composition and structure of activated PPG were analyzed using laser particle size testing. The grinding kinetics mechanism was analyzed based on classification theory, and its chemical activity was characterized through activity index testing. Results indicate that after 30 min of grinding, the median particle size of PPG powder increases to 83.42 μm. The specific surface area reaches 5.2729 m²/g, and the morphology shows agglomeration, forming spherical structures of varying sizes. When grinding exceeds 60 min, the median particle size of PPG decreases to 32.45–37.88 μm. The spherical structures shatter and become irregular fragments. The Swebrec function and RRB are suited for describing the grinding kinetics of PPG in the initial (less than 60 min) and the later (more than 60 min) stage of grinding, respectively, and the fractal characteristic curve of PPG powder adheres to a linear fitting law. As curing time increases, the activity index of PPG cement mortar test blocks rises by 30.7–56.5 %. After 28 days of curing, the highest activity index value exceeds 75 %, meeting the requirements for S75 grade slag grinding particles according to the Chinese national standard GB/T 18046–2017.
Mechanical ball milling significantly enhances the recovery rate and utilization efficiency of phosphogypsum (PPG). This study investigates the mechanical activation of PPG. Mechanical ball milling was conducted at a speed of 300 r/s for periods ranging from 30 to 120 min. The particle composition and structure of activated PPG were analyzed using laser particle size testing. The grinding kinetics mechanism was analyzed based on classification theory, and its chemical activity was characterized through activity index testing. Results indicate that after 30 min of grinding, the median particle size of PPG powder increases to 83.42 μm. The specific surface area reaches 5.2729 m²/g, and the morphology shows agglomeration, forming spherical structures of varying sizes. When grinding exceeds 60 min, the median particle size of PPG decreases to 32.45–37.88 μm. The spherical structures shatter and become irregular fragments. The Swebrec function and RRB are suited for describing the grinding kinetics of PPG in the initial (less than 60 min) and the later (more than 60 min) stage of grinding, respectively, and the fractal characteristic curve of PPG powder adheres to a linear fitting law. As curing time increases, the activity index of PPG cement mortar test blocks rises by 30.7–56.5 %. After 28 days of curing, the highest activity index value exceeds 75 %, meeting the requirements for S75 grade slag grinding particles according to the Chinese national standard GB/T 18046–2017.
关键词：
High alumina fly ash;Mechanical milling;Grinding kinetics;Microstructure;Activation mechanism
摘要：
Mechanical force can significantly enhance the physical and chemical activity of high-alumina fly ash (HAFA). Microparticle fly ash (MFA) was produced through mechanical ball milling of HAFA. The study concentrated on the particle size distribution of MFA after ball milling for 30–90 min and examined the impact of triethanolamine as a grinding aid. The particle size distribution (PSD), grinding kinetics, and mechanisms of microstructure evolution were analyzed. To verify the chemical activity of MFA, a high-alumina fly ash-based environmental material (EMFA) was synthesized. The results indicated that the particle proportion of 1–10 μm in MFA exceeded 50 %, and the RRB function was more suitable for describing the grinding kinetics of MFA. The mineral structure exhibited an increase in the content of amorphous substances, leading to the formation of amorphous active aluminum (Al). The microstructure of MFA displayed a combination of gel-like and fiber-like structures, including large smooth areas and fragment stacking. However, after 90 min of ball milling, a dense pore structure formed. The addition of triethanolamine accelerated the fragmentation of large particles and the formation of a secondary aggregate structure, with D50 remaining stable between 5.424 and 5.736 μm. The maximum compressive strength of EMFA reached 22.34 MPa, meeting the MU20 level of the Chinese standard "Solid Concrete Brick" (GB/T 21144-2023). This study provides crucial theoretical support for the modification, activation, and resource utilization of HAFA.
Mechanical force can significantly enhance the physical and chemical activity of high-alumina fly ash (HAFA). Microparticle fly ash (MFA) was produced through mechanical ball milling of HAFA. The study concentrated on the particle size distribution of MFA after ball milling for 30–90 min and examined the impact of triethanolamine as a grinding aid. The particle size distribution (PSD), grinding kinetics, and mechanisms of microstructure evolution were analyzed. To verify the chemical activity of MFA, a high-alumina fly ash-based environmental material (EMFA) was synthesized. The results indicated that the particle proportion of 1–10 μm in MFA exceeded 50 %, and the RRB function was more suitable for describing the grinding kinetics of MFA. The mineral structure exhibited an increase in the content of amorphous substances, leading to the formation of amorphous active aluminum (Al). The microstructure of MFA displayed a combination of gel-like and fiber-like structures, including large smooth areas and fragment stacking. However, after 90 min of ball milling, a dense pore structure formed. The addition of triethanolamine accelerated the fragmentation of large particles and the formation of a secondary aggregate structure, with D50 remaining stable between 5.424 and 5.736 μm. The maximum compressive strength of EMFA reached 22.34 MPa, meeting the MU20 level of the Chinese standard "Solid Concrete Brick" (GB/T 21144-2023). This study provides crucial theoretical support for the modification, activation, and resource utilization of HAFA.
摘要：
Marine soft soils, characterized by high water content and low strength, present significant challenges to foundation stability. These soils often lead to settlement and uneven deformation, posing risks to infrastructure safety. This study tackles these challenges and promotes industrial waste utilization by developing a novel curing material for marine soft soils. The material consists of ground granulated blast furnace slag (GGBS), phosphogypsum (PG), and calcium carbide slag (CCS), and is compared to ordinary Portland cement (OPC). A D-optimal design was employed to establish regression equations for unconfined compressive strength (UCS) at 7 and 28 days. The interactions between factors were analyzed to optimize the mix ratio. The effects of different curing ages on the unconfined compressive strength, modulus of elasticity, moisture content, and pH of GPCOR solidified soft soil and cement solidified soil were investigated. The microstructure of the solidified soils was analyzed using SEM, XRD, FTIR, and BET techniques. The results indicated that the optimal GPC ratio was GGBS: PG: CCS = 64.81: 20.00: 15.19. After 28 days, GPCOR solidified soil exhibited superior UCS (4.48 MPa), 1.47 times greater than that of OPC solidified soil, and a deformation modulus 2.04 times higher. Furthermore, GPCOR exhibited a denser microstructure with smaller average pore sizes, improved durability, and better water retention than OPC. These findings underscore the potential of GPC as a sustainable alternative to conventional cement for reinforcing marine soft soils, promoting both soil stabilization and industrial waste resource utilization.
Marine soft soils, characterized by high water content and low strength, present significant challenges to foundation stability. These soils often lead to settlement and uneven deformation, posing risks to infrastructure safety. This study tackles these challenges and promotes industrial waste utilization by developing a novel curing material for marine soft soils. The material consists of ground granulated blast furnace slag (GGBS), phosphogypsum (PG), and calcium carbide slag (CCS), and is compared to ordinary Portland cement (OPC). A D-optimal design was employed to establish regression equations for unconfined compressive strength (UCS) at 7 and 28 days. The interactions between factors were analyzed to optimize the mix ratio. The effects of different curing ages on the unconfined compressive strength, modulus of elasticity, moisture content, and pH of GPCOR solidified soft soil and cement solidified soil were investigated. The microstructure of the solidified soils was analyzed using SEM, XRD, FTIR, and BET techniques. The results indicated that the optimal GPC ratio was GGBS: PG: CCS = 64.81: 20.00: 15.19. After 28 days, GPCOR solidified soil exhibited superior UCS (4.48 MPa), 1.47 times greater than that of OPC solidified soil, and a deformation modulus 2.04 times higher. Furthermore, GPCOR exhibited a denser microstructure with smaller average pore sizes, improved durability, and better water retention than OPC. These findings underscore the potential of GPC as a sustainable alternative to conventional cement for reinforcing marine soft soils, promoting both soil stabilization and industrial waste resource utilization.
通讯机构：
[Wu, K ] S;Shandong Univ, Sch Civil Engn, Jinan 250061, Peoples R China.
关键词：
Constitutive model;Disturbed state concept;Geotechnical tests;Marine soft soil;Numerical calculation
摘要：
Marine soft soils are widely distributed in near-coastal areas and pose significant risks to the stability of structures due to their unique mechanical properties. While researchers worldwide have used various theoretical constitutive models and scientific methods to investigate the mechanical properties of marine soft soils, no attempts have been made to establish a mechanical model based on the concept of disturbed state for marine soft soils. In this paper, based on the concept of disturbed state, we utilize triaxial and creep test methods, apply the Duncan tensor modulus to describe the relatively complete state of marine soft soil, and modify the Cambridge model to characterize the fully adjusted state. Additionally, we derive the disturbance function to establish the intrinsic model for the disturbed state of marine soft soil. The model's accuracy is verified by comparing its predictions with experimental test results. Subsequently, the model is applied to engineering cases and compared with numerical simulation results. The study shows that the results from the disturbed state constitutive model are consistent with the experimental data and can effectively be used to assess the foundation bearing capacity of marine soft soil layers. The development of the constitutive model based on the concept of disturbed state offers a new theoretical framework and calculation method for studying the mechanical properties of marine soft soil in near-coastal regions.
摘要：
Carbon dots (CDs), as a revolutionary nanomaterial, exhibit unique advantages in terms of wastewater treatment, offering new opportunities for the development of water treatment technologies due to their simple synthesis methods, excellent biocompatibility, tunable optical properties, and favorable environmental performance. This review systematically discusses the synthesis methods, structural characteristics, and application progress of carbon dots in wastewater treatment, highlighting several key findings. (1) Excellent adsorption performance: CDs can effectively remove heavy metal ions, dyes, and organic pollutants from water. (2) Outstanding photocatalytic performance: Some carbon-dot-enhanced photocatalytic systems can efficiently remove pollutants under visible light. (3) Exceptional selective detection ability: CDs are capable of highly sensitive detection of heavy metals and organic pollutants in water, with the detection limits reaching the nanomolar level. (4) Enhanced membrane separation performance: The high water flux and excellent selectivity of carbon-dot-modified membranes make them suitable for efficient water treatment and water quality separation. (5) Enhancement of biological treatment: In biological treatment systems, CDs can significantly improve the microbial activity and electron transfer efficiency to enhance the efficiency of biological degradation processes. (6) Sustainable utilization of waste as a raw material and regeneration of CDs are conducive to reducing the cost of preparation of CDs. These findings indicate that CDs have broad application potential in wastewater treatment. Furthermore, this review looks ahead to the future development directions of CDs in wastewater treatment, proposing potential innovations in catalytic performance enhancement, cost control, and practical applications, aiming to provide important references and guidance for future research and industrial application of CDs in wastewater treatment.
摘要：
Geopolymers are coating materials with excellent properties that have received considerable attention due to their high resistance to weathering, chemical attack, abrasion, and adhesion. This paper further investigates the performance of geopolymer-based coatings by examining the effect of varying percentages of zinc oxide on their antimicrobial and durability properties. The performance of the coatings was evaluated following durability tests with the incorporation of different zinc oxide doping levels. Furthermore, to demonstrate the degree of antibacterial properties of the coating, test plates were treated with two common fungi and bacteria, and the number of bacterial colonies was observed. Results showed good stability and antimicrobial properties when coating with ZnO.
摘要：
Cr(VI)-contaminated soil is frequently encountered at abandoned industrial sites, posing a significant threat to surrounding ecosystems and human health. In this study, a novel of slag-phosphogypsum-based environmental material (SPEM) was developed using granulated blast furnace slag and phosphogypsum as raw materials under alkaline activation. Unconfined compressive strength tests, volume shrinkage tests, and toxicity leaching tests were conducted to evaluate the mechanical strength, volume shrinkage, and Cr(VI) ion leaching concentration of the solidified contaminated soil. Characterization of the solidified environmental material blocks (EMB) was performed using X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate that as the SPEM content and curing period increase, the unconfined compressive strength of Cr(VI)-contaminated soil (cured for 14 days at a fivefold pollution level) increases by 58.457 % before declining to 4.867 MPa. Meanwhile, the Cr(VI) ion leaching concentration decreases to 0.099 mg/L. The leaching concentration of Cr(VI) in SPEM containing 5 %, 10 %, 15 %, and 20 % for 14 days ranged from 0.099 mg/L to 0.379 mg/L, significantly lower than the emission limit specified in the "Integrated Wastewater Discharge Standard" (GB8978-1996). The heavy metal Cr(VI) is chemically immobilized and physically encapsulated within SPEM. This study provides experimental validation for the remediation and ecological restoration of Cr(VI)-contaminated soil.
关键词：
Anammox;Biochar;Fe3+;Nitrogen removal performance;Global warming potential;Microbial community
摘要：
Anammox is a new type of autotrophic nitrogen removal technology with high efficiency and low consumption. However, the long start-up time and poor running stability of Anammox seriously restrict its large-scale application. In this study, simultaneously addition strategy of Fe 3+ and reed straw biochar was developed to improve the nitrogen removal performance of Anammox. The nitrogen removal was highest in Anammox system with simultaneously addition of Fe 3+ and reed straw biochar prepared at 600 °C for 2 h. And continuous addition of Fe 3+ in the Anammox system with reed straw biochar not only exhibit high nitrogen removal efficiency and excellent resistance to nitrogen shock loading, but also had low global warming potential (GWP). Genus Candidatus Brocadia as dominant AnAOB had the highest relative abundance with the simultaneously addition of Fe 3+ and reed straw biochar. Besides, enrichment of iron oxidation–reduction microorganisms through enhancing extracellular electron transfer with reed straw biochar achieved the coupling of Anammox, Feammox and NDFO, which was significantly facilitated the nitrogen removal performance of Anammox.
Anammox is a new type of autotrophic nitrogen removal technology with high efficiency and low consumption. However, the long start-up time and poor running stability of Anammox seriously restrict its large-scale application. In this study, simultaneously addition strategy of Fe 3+ and reed straw biochar was developed to improve the nitrogen removal performance of Anammox. The nitrogen removal was highest in Anammox system with simultaneously addition of Fe 3+ and reed straw biochar prepared at 600 °C for 2 h. And continuous addition of Fe 3+ in the Anammox system with reed straw biochar not only exhibit high nitrogen removal efficiency and excellent resistance to nitrogen shock loading, but also had low global warming potential (GWP). Genus Candidatus Brocadia as dominant AnAOB had the highest relative abundance with the simultaneously addition of Fe 3+ and reed straw biochar. Besides, enrichment of iron oxidation–reduction microorganisms through enhancing extracellular electron transfer with reed straw biochar achieved the coupling of Anammox, Feammox and NDFO, which was significantly facilitated the nitrogen removal performance of Anammox.
摘要：
A series of cyclic triaxial tests were conducted on marine soft clay deposits to establish and validate a predictive model for cumulative plastic strain. Additionally, a numerical model of particle flow code in cyclic triaxial tests was developed. The effects of confining pressure, moisture content, and dynamic stress ratio on the dynamic properties of marine soft clay were examined, considering factors such as volume deformation and microscopic failure patterns. The results indicated that both the predictive model and numerical model showed strong consistency with the experimental data. The plastic strain of marine soft clay was influenced by moisture content, stress ratio, and confining pressure in a consistent manner, with moisture content being the primary factor. A predictive model for the cumulative plastic strain of marine soft clay was successfully established, allowing for the evaluation of dynamic properties from the perspective of cumulative plastic strain. During the loading process in the numerical model, microcracks within the soil structure gradually compacted, and the main displacement of the specimen extended from the vertical center axis to the sides, ultimately resulting in shear damage.
摘要：
Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 x 10-6 cm2/s-9.5 x 10-6 cm2/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 x 10-8 to 4.13 x 10-7 cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills.
摘要：
Landfills necessitate a liner barrier system to prevent the leakage of contaminants into the surrounding soil. However, the currently employed compacted clay liner (CCL) is insufficient to prevent the leakage of heavy metal ions. This study proposes a novel landfill liner system utilizing sludge-based activated carbon (SAC)-modified clay. The adsorption characteristics of SAC-modified clay liner (SAC-CCL) for Cd(II) or Cu(II) were evaluated through batch tests. The permeability coefficient and unconfined compressive strength of SAC-CCL were assessed through permeation and unconfined compression tests. The permeability coefficient of the SAC-modified clay ranged from 2.57 x 10(-9) to 1.10 x 10(-8) cm/s. The unconfined compressive strength of the SAC-CCL varied between 288 and 531 kPa. The migration of Cd(II) or Cu(II) within an 80 cm thick, full-scale SAC-CCL was simulated using soil column tests. The diffusion coefficient (D) was calculated by inversion using the one-dimensional solute migration equation. The diffusion coefficients (D) for Cd(II) and Cu(II) ranged from 1.9 x 10(-10) to 13.5 x 10(-10) m(2)/s. The retardant performance of SAC-CCL for Cd(II) and Cu(II) followed the order: 3% SAC-CCL > 1% SAC-CCL > CCL > 5% SAC-CCL, from strongest to weakest. Consequently, SAC-modified clay demonstrates significant potential as a landfill lining material. However, the migration behavior of heavy metal ions in SAC-CCLs under cyclic dry-wet conditions requires further investigation.
摘要：
This study introduces a novel landfill cover material, employing lake sediment as a substrate, stabilised with fly ash, slag, desulfurisation gypsum and construction waste. The mechanical properties, including shear strength parameters, unconfined compressive strength, hydraulic conductivity, volumetric shrinkage, and water content, of the solidified sludge were evaluated. The microscopic mechanism of the solidified sludge were investigated through XRD, FTIR, and SEM-EDS techniques. A novel three-layer composite capping cover system for landfills is proposed, comprising an upper capillary barrier layer, a middle drainage layer and a bottom impermeable layer . Indoor rainfall simulation tests were conducted to assess the water retention performance of this capping cover system under repeated moderate, heavy, and torrential rainfall events. The early strength of the solidified sludge exhibited rapid development, with cohesion and internal friction angle reaching 382.56 kPa and 57.67°, respectively, after 3 days. After 28d, the unconfined compressive strength ranged from 6.93 to 14.29 MPa, with hydraulic conductivity between 3.98-23.1 × 10(-8)cm/s. The hydration reactions of the industrial waste residues resulted in the formation of Ettringite, Gypsum, and hydrous calcium (aluminum) silicates. The Ettringite and Gypsum crystals formed an internal support framework, while the generation of gel-like substances such as C-S-H and C-A-S-H facilitated product aggregation. The RSM was employed to optimise the material ratio of the solidified sludge, while the Pearson coefficient facilitated correlation analysis. This study provides valuable data for designing landfill solidified sludge cover systems and offers a new approach for the co-disposal of sludge and industrial waste.
摘要：
High-speed sliding often leads to catastrophic landslides, many of which, in the initial sliding phase before disintegration, experience a friction-induced thermal pressurization effect in the bottom shear band, accelerating the movement of the overlying sliding mass. To quantitatively investigate this complex multiphysical phenomenon, we established a set of equations that describe the variations in temperature and excess pore pressure within the shear band, as well as the conservation of momentum equation for the overlying sliding mass. With a simplified landslide model, we investigated the variations of temperature and excess pore pressure within the shear band and their impacts on the velocity of the overlying sliding mass. On this basis, we studied the impact of seven key parameters on the maximum temperature and excess pore pressure in the shear band, as well as the impact on the velocity of the overlying sliding mass. The simulation results of the standard model show that the temperature and excess pore pressure in the shear band are significantly higher than those in the adjacent areas, and reach the maximum values in the center. Within a few seconds after the start, the maximum excess pore pressure in the shear zone is close to the initial stress, and the shear strength loss rate exceeds 90%. The thermal pressurization mechanism significantly increases the velocity of the overlying sliding mass. The results of parameter sensitivity analysis show that the thermal expansion coefficient has the most significant impact on the temperature and excess pore pressure in the shear band, and the sliding surface dip angle has the most significant impact on the velocity of the overlying sliding mass. The results of this study are of great significance for clarifying the mechanism of thermal pressurization-induced high-speed sliding.
摘要：
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.
摘要：
Desert areas pose challenges for building construction due to extreme temperatures, low humidity, and water scarcity. These factors contribute to the rapid drying of self-bonding materials, leading to poor stability of materials. This study aims to address these issues through a novel approach involving the collaborative utilization of natural aeolian sand (NAS) and secondary aluminum dross (SAD) for the synthesis of self-bonding materials. By utilizing CaO as an alkali activator, NAS, and SAD are subjected to mechanical grinding, leading to the successful production of self-bonding materials for the first time. The results indicated that when the ball grinding rotational speed was 550 rpm, the mass ratio of NAS to SAD was 1:1, and 5% calcium oxide was added, a 360-day compressive strength of 8.57 MPa was achieved for self-bonding materials. Under the synergistic action of mechanical collisions and high temperature, the mineral lattice of SAD was defected, and amorphous substances was appeared, the majority of the Si-O chemical bonds and Al-N bonds were broken by alkaline attack, forming a more stable structure (Si-O-Al). This approach enables the full-volume materialization of hazardous and bulk solid wastes while opening up new possibilities for municipal building materials in desert areas. Furthermore, the proposed method provides an economically viable and environmentally friendly solution for the treatment of 1.3 million km 2 of desert and two million tons of SAD in China.
Desert areas pose challenges for building construction due to extreme temperatures, low humidity, and water scarcity. These factors contribute to the rapid drying of self-bonding materials, leading to poor stability of materials. This study aims to address these issues through a novel approach involving the collaborative utilization of natural aeolian sand (NAS) and secondary aluminum dross (SAD) for the synthesis of self-bonding materials. By utilizing CaO as an alkali activator, NAS, and SAD are subjected to mechanical grinding, leading to the successful production of self-bonding materials for the first time. The results indicated that when the ball grinding rotational speed was 550 rpm, the mass ratio of NAS to SAD was 1:1, and 5% calcium oxide was added, a 360-day compressive strength of 8.57 MPa was achieved for self-bonding materials. Under the synergistic action of mechanical collisions and high temperature, the mineral lattice of SAD was defected, and amorphous substances was appeared, the majority of the Si-O chemical bonds and Al-N bonds were broken by alkaline attack, forming a more stable structure (Si-O-Al). This approach enables the full-volume materialization of hazardous and bulk solid wastes while opening up new possibilities for municipal building materials in desert areas. Furthermore, the proposed method provides an economically viable and environmentally friendly solution for the treatment of 1.3 million km 2 of desert and two million tons of SAD in China.
摘要：
This paper utilizes industrial wastes, including slag powder, desulfurized gypsum, fly ash, and construction waste, to solidify municipal sludge and develop a new type of landfill cover material. To investigate the durability of solidified sludge under wet-dry cycles, this study systematically analyzes its mechanical properties-such as volume shrinkage rate, unconfined compressive strength, and permeability coefficient-along with microstructural characteristics like pore structure, micro-morphology, and hydration products. In addition, the impermeability of the solidified sludge cover under varying rainfall conditions was assessed using rainfall simulation tests. After 20 wet-dry cycles, the solidified sludge samples exhibited volume shrinkage between 0.56% and 0.85%, unconfined compressive strength from 1.31 to 4.55 MPa, and permeability coefficients ranging from 9.51 x 10- 8 to 5.68 x 10- 7 cm/s. Portions of the gelatinous hydration products in the solidified sludge experienced discrete damage, leading to an increase in microporous volume. However, the overall structural integrity of the solidified sludge was maintained. The 3-layer landfill cover system was constructed using engineering soil, coarse construction waste aggregate, and solidified sludge and resisted strong precipitation. The 40 cm thick solidified sludge acted as an impermeable layer and yielded a good water-blocking effect. This study provides data support the application and technical advancement of solidified sludge as a landfill cover material.
