Abstract:For engineering practice, conducting experiments with different stress paths to study the mechanical characteristics of rock masses is essential. In order to study the mechanical characteristics of siltstone under the special stress path of cyclic unloading-loading of confining pressure, the MTS815 rock mechanics testing system was used to conduct staged cyclic unloading-loading confining pressure tests at different axial force levels, and the evolution characteristics of axial and circumferential plastic strain and elastic modulus at different stress levels were analyzed. The relationship between the energy evolution and the deformation as well as the damage of the specimens was also analyzed via calculation of dissipated energy. The results show that the hysteresis loops move in the direction of strain increase as the number of cycles increases, and the stress-strain curves of unloading-loading confining pressure gradually close, and the overall change of hysteresis loop spacing is from “sparse” to “dense”. The lower the unloading level is, the lower the modulus of elasticity is, while the lower the stress level is, the higher the modulus of elasticity is. Modulus of elasticity is affected by both the axial force level and the unloading level; the circumferential plastic strain is generally larger than the axial value in a single cycle, and the resistance to plastic deformation at high axial force levels is stronger than that at low force levels under the special stress path; the total energy dissipated in the final damage of the rock is positively correlated with the axial force level to some extent.

Abstract:In order to explore the effect of lignin on weak expansive soil in Xinxiang area, the physical and mechanical properties of weak expansive soil in Xinxiang area with different lignin contents were examined by laboratory test and ESEM (Environmental Scanning Electron Microscope) test. The microstructure characteristics and pore morphology characteristics of the improved soil with different lignin contents were qualitatively described and quantitatively characterized. Based on the XRD ( X-Ray Diffraction ) testing results, the changes of mineral composition in the improved soil were discussed, so as to reveal the interaction mechanism between lignin and soil. The test results show that when lignin is used to improve expansive soil, 3% lignin has the optimal effect on inhibiting the expansion, and simultaneously the compressive strength reaches the maximum, while the compressive strength of soil decreases after exceeding the optimal dosage. The pore structure in the soil is complex, the pore arrangement is disordered and the orientation is less satisfactory. The lignin cement can fill the soil pores to make its microstructure more dense. Lignin plays a cementing role in expansive soil, and cannot react with expansive soil to form new mineral components. It has satisfactory stability when interacting with soil, which belongs to physical improvement. As an efficient and environmentally friendly modifier, lignin can effectively improve the basic engineering properties of expansive soil, of which further study is promising.

Abstract:Carbonation is an important factor affecting the durability of cement-solidified heavy metal-contaminated soils. In order to explore the influence of carbonation on the strength of solidified contaminated soils, lead-contaminated soils were artificially prepared, and carbonation tests were carried out after cement solidification treatment. The effects of carbonation and compactness on unconfined compressive strength(UCS) of solidified soils were analyzed, and the effects of carbonation on micro mineral morphology and micro pore structure were also analyzed by electron microscope scanning and mercury injection tests. The test results show that UCS of solidified lead-contaminated soils decreases under carbonation, the strength of solidified soils with 15% cement content is reduced by 44%-45%, which is the result of the filling enhancement effect of carbonation reaction products and the weakening of cementation between soil particles. There is a good power function relationship between UCS and porosity of solidified soils, which reveals the influence of filling on strength of solidified soils. Under carbonation, crystalline carbonation reaction product CaCO₃ is observed, the total pore volume of solidified soils decreases, the proportion of gel pores less than 0.01 μm and capillary pores between 0.01 μm and 0.1 μm decreases, and the proportion of capillary pores between 0.1 μm and 10 μm and macro pores greater than 10 μm increases.

Abstract:In the electro-chemical reinforcement method, the type of injecting solutions has been one of the main research issues. The injection of chemical solution has a significant impact on the electrokinetic properties of the soil, and the main influential factors include the types of cation, ion concentration, cation valence, cation radius, etc. of the injecting solutions. The change of the electrokinetic properties of the soil has a non-negligible impact on the electro-osmotic reinforcement effect. In order to study the effect of cation radius in injecting chemical solutions on the effect of electro-chemical reinforcement of soft soil foundation, taking the divalent metal ions Ca²⁺, Mg²⁺， Cu²⁺ with different radii of the same valence as research objects, the changes of current, drainage volume, electric permeability coefficient during the test and the distribution of water content and shear strength after test were analyzed, combined with scanning electron microscope(SEM) to explore the effect of different radii of cations on the electro-chemical reinforcement effect. The results show that increasing the ionic radius can significantly improve the current, drainage rate, electric permeability coefficient and shear strength of the soil after treatment. Among them, the cation radius of Ca²⁺ is the greatest, and the reinforcement effect of calcium ions is the best. The SEM images also show that soil compactness is higher after calcium ion treatment.

Abstract:With fundamental research on geopolymer, the study of using geopolymer as solidification agent in the field of soil stabilization has received extensive attention. Geopolymer, as a new soil solidification agent, is a kind of green inorganic cementitious material formed by aluminosilicate-rich minerals as precursors under the action of alkali activators. It is equipped with the advantages of good mechanical properties, great durability, low carbon and environment friendly, etc. It can effectively overcome the disadvantages of high energy consumption, high pollution and poor durability of traditional soil solidification agents such as cement or lime, and is generally considered as an ideal substitute for traditional soil solidification agents. In order to clarify the solidification mechanism and reinforcement effect of geopolymers on soil, the research progress of geopolymer solidified soil in recent years is reviewed in this paper. Firstly, the reaction mechanism of geopolymer solidified soil is introduced; secondly, the influence of different factors on the mechanical properties such as unconfined compressive strength and shear strength is described in detail; thirdly, the durability of geopolymer solidified soil under freeze-thaw cycle, dry-wet cycle and chemical ion erosion is discussed; finally, the future study of geopolymer solidified soil technique is prospected.

Abstract:Chemical corrosion has a degrading effect on the mechanical properties of rock masses. The rock masses in engineering practice is generally facing dynamic impact loading such as drill burst excavation and mechanical rock breaking, moreover, the destruction of rock is essentially a process of energy absorption and dissipation. Therefore, it is of great practical significance to study the energy evolution of corroded rock under impact loading. Dynamic impact tests were conducted on granite specimens after soaking in KHSO₄ solutions at 2 different pH values (3 and 5) using the Split Hopkinson Pressure Bar (SHPB) system. Corrosion time was set to 30 and 60 days, and another set of specimens without corrosion was set up as control group, in order to investigate the energy evolution of granite after acidic corrosion under air chamber pressures of 0.15 MPa. The change laws of dynamic stress-strain curve, peak stress, peak strain, and energy absorption rate with pH value and corrosion time were given. It was found that with the decrease of pH value and the increase of corrosion time, the nonlinear stage of dynamic stress-strain curve was compressed, the peak stress and peak strain decreasing. Moreover, the energy absorption rate increased from 37.39% to 52.11% after 60 days of corrosion in solutions of pH=3, indicating that with increase of chemical corrosion, the strength of granite decreased, the deformation ability becoming worse, stress waves consuming more energy as they propagate through the interior of samples and the specimens were more easily damaged.

Abstract:Assessment of landslide hazards is important in highway engineering especially considering the landslide hazards along challenging roads; more research is needed to understand progressive strategies. Therefore, multidisciplinary and advanced methodologies were needed to assess the formation mechanisms and stability of complex landslides on the Muzaffarabad-Mansehra Highway in northern Pakistan. The main study objectives were to investigate slope failures, identify the triggering mechanism of layered rocks, image subsurface geometrical configurations, and assess slope stability factors using field operations, remote-sensing tools, geomorphological mapping, geophysical imaging, and kinematics analysis. The findings indicate that the foliated Hazara Formation, being buckled easily, is particularly susceptible to the geo-environmental conditions that triggered the landslide. Geophysical surveys revealed multiple layers of varying depth and thickness, highlighting the complexity of the landslide. Low resistivity zones (0.325-1 350 Ω·m) indicated the presence of un-onsolidated, water-saturated materials and highly sheared substances, whereas high resistivity zones (1 510-26 092 Ω·m) were associated with overburden, including alluvium, boulders, and dry slate fragments. Seismic refraction tomography indicated low P-wave velocities (400-1 800 m/s) within highly saturated overburdens, reworked blocks, and surficial weathering. The subsurface layers are interspersed with fragmented pieces of high-density rock and massive boulders, displaying P-wave velocities within the range of 3 000-5 000 m/s. Both tomographic methods revealed a fracture zone extending 30 m depth, which poses a significant risk of catastrophic occurrences. The sliding surface was found to be 25-30 meters depth at the crown and 45 meters depth in the main body. Kinematic analysis identified wedge failure as the primary failure mode along highway cuts. The findings of this study demonstrate the significance of employing integrated techniques to analyze the underlying mechanics of landslide hazards within the context of highway engineering. Furthermore, these integrated procedures are highly advantageous in efficiently eliminating the associated risks posed by such hazards.

Abstract:The stability of mine slope is a major safety and production problem that affects mining practice. A safe environment is an important prerequisite for mining. Therefore, mine slope stability analysis has important guiding significance for safety production. This paper takes the Huanghua limestone mine slope in Chongqing as an example to perform a numerical modeling analysis. Firstly, the unmanned aerial vehicle (UAV) was used to obtain the geometric shape of the mine slope and identify the rock structure surface, and a 3D geologic model was created based on photographic identification results. Then, the finite element strength reduction method was used to compare the stability of the slope of the mine under natural condition and heavy rain condition, and the influences of rainfall on slope stability were revealed. The results show that under the condition of heavy rain, the slope deformation and strain are larger than those under natural conditions, and the safety factor is smaller. Specifically, the deformation and strain under heavy rain are 30% and 40%-60% higher than that under natural condition. The safety coefficient decreased by 5%-7%, and the numerical simulation results were basically reasonable. The stability of the mine slope is high, and the possibility of overall slip failure is low. However, the risk of local block falls should be prevented, and further research is needed to determine whether local slope reinforcement is required. In addition, the research results of this article verified the applicability and reliability of the comprehensive research methods of on-site investigation, lab testing, preliminary determination of 3D models, and key analysis of 2D profiles for evaluating the stability of rock slopes.

Abstract:In view of the existing problems of confined water risk analysis of deep foundation pit, such as single analysis method, insufficient risk prior assessment theory and lack of dynamic risk prediction during the construction process, this paper proposed a confined water risk analysis method of deep foundation pit based on Bayesian network (BN) to realize the pre-analysis of confined water risk accidents and the dynamic risk evaluation of the whole construction process. From aspects of environment, design, construction and management, the method established a risk evaluation index system of confined water of deep foundation pit, constructed static BN risk analysis model, and completed the risk probability prediction, accident factor diagnosis, disaster factor identification and other risk assessment contents in advance. On this basis, the dynamic risk analysis of confined water in the whole construction process based on monitoring data was realized by setting risk transfer nodes and observation nodes and introducing Noisy-Max hypothesis. Finally, taking the north deep foundation pit of Jingjiang Yangtze River tunnel project in Jiangyin as an example, the risk level of confined water in the project was analyzed, the related risk factors were further defined, and the dynamic risk change was accurately predicted. Results show that the proposed method has high applicability and can provide practical guidance for the safety of deep foundation pit construction.

Abstract:To study the stability of the tunnel face for dual-mode shield machine excavated in a composite strata, a two-dimensional failure mechanism of the tunnel face was constructed by using spatial discretization technique. The objective function of the soil chamber pressure in the limit state was derived by using this failure mechanism and the upper limit theorem of limit analysis. The upper bound solution of the soil chamber pressure to maintain the stability of tunnel face during the shield machine pass through the interface of the soil/rock was obtained from optimization. Moreover, the influence of different parameters on the soil chamber pressure and the failure mode of the tunnel face were discussed. On this basis, based on the probabilistic theory, the reliability model of the soil chamber pressure was established, and the minimum soil chamber pressure which was used to maintain the stability of tunnel face in composite stratum with a tolerable reliability was given. Parametric analysis shows that the soil chamber pressure decreases as the distance between the shield machine and interface of the soil/rock shortens, and failure region in front of the tunnel face increases with the increase of the interface inclination angle.

Abstract:It’s of great significance for engineering practice to study the variation of pore water pressure increment and effective radial stress at the pile-soil interface caused by jacked pile-sinking in saturated clayey soil. Embedded installation of micro test elements on the surface of the open and closed piles was realized. Then the effective radial stress of the pile-soil interface considering the increase of pore pressure was successfully obtained by using large-scale model test system and double-walled open and closed model pipe pile. The results show that the excess pore water pressure and effective radial stress of pile-soil interface increase with the embedded depth. The excess pore water pressure at the pile-soil interface of closed pile is greater than open pile. The excess pore water pressure and effective radial stress of upper part of pile is less than lower part of pile. At the same depth of penetration, with the increase of h/L of the pile body, there is a phenomenon of lateral pressure “degradation” in the soil pressure of the pile-soil interface. Under specific test conditions, the maximal ratio of excess pore water pressure of pile-soil interface and effective pressure of superimposed soil of open and closed pile are 61.2% and 52.1%. The effective radial stress of the pile-soil interface is 3.76-5.46 times of excess pore water pressure. Therefore, the change of excess pore water pressure and effective earth pressure of pile-soil interface are related to variation of pile locations of h/L at different penetration depths.

Abstract:X-section cast-in-place concrete pile (XCC pile), as a non-circular sectional special-shaped pile, turned the circular arch into reverse arch based on the principle of constant sectional special-shaped periphery enlargement, to turn the circular arc positive arch into an anti-arch, and finally forms a symmetrical X-shaped section, to expand the section perimeter and improve the bearing capacity. The installation process of XCC piles is actually a process of soil squeezing, and the effect of soil squeezing of pile group penetration is more complicated than that of single pile. However, there is limited research on the effect of soil squeezing of XCC piles group penetration at present, and the effect of soil squeezing of XCC pile group penetration is an important topic in the study of XCC piles. The effects of different pile types and different pile sequences on the squeezing effect of pile group penetration are studied. Based on the transparent soil technique, the penetration test of XCC pile and circular pile group was carried out. The displacement field variation pattern of pile group penetration was obtained via particle image velocimetry, and the influence of different pile types and penetration sequences on squeezing effect of pile group was studied. Results show that obvious cumulative effect and shielding effect can be observed during the penetration of XCC and circular group piles. For the displacement of the soil of the last penetrated pile dorsal surface, the displacement caused by XCC piles penetration reaches the peak first than that of the circular piles, and both XCC piles and round piles penetration produce obvious cumulative effect and shielding effect. The shielding effect of XCC pile is stronger than that of circular pile. Finally, empirical formula for predicting the shielding effect for XCC and circular piles under different penetration sequences was provided.

Abstract:In order to obtain the optimal design scheme of a foundation pile that meets the reliability requirements, the construction cost of foundation piles should be reduced as much as possible under the condition of effectively controlling the settlement of foundation piles. In this paper, the foundation pile of the China Zun Mansion is taken as an example, and the inherent uncertainty in the ultimate resistance of soils is considered. The non-dominated sorting genetic algorithm-II (NSGA-II) is used, which includes the non-dominated solution selection sorting and crowing distance comparison for individuals in a population. In this algorithm, the pile diameter and pile length are regarded as optimal design variables, the targeted reliability index of the bearing capacity for foundation pile is taken as constraint condition, and the minimum engineering cost and the lowest settlement is taken as an objective function. The Pareto optimal solution set is obtained, and a few shortcomings are resolved, such as the poor optimization performance and slow speed of traditional multi-objective optimization methods in the absence of experience. Moreover, each solution in the Pareto optimal solution set is weighted by using the TOPSIS method based on the entropy weight theory, the best scheme is chosen with the largest relative closeness. The results show that the chosen scheme is slightly better than the original design scheme in terms of construction cost and pile settlement, which demonstrates that the proposed optimal design method for foundation piles is feasible.

Abstract:Excessive loading in soft soils will cause significant displacement of adjacent bridge pile foundations, which is extremely detrimental to the safe service of the bridge. Combined with an actual pier deviation case in soft soil caused by surcharge loads, a material model subroutine considering the time-dependent characteristics of lateral deformation of soft soil was proposed, and a finite element model of surcharge load-pile foundation-bridge pier structure was established to study the time-dependent deviation characteristics of bridge pier-cap-pile foundation structure in soft soil area under surcharge loads and to reveal the lateral-deviation mechanism of the bridge pier-cap-pile foundation structure. In addition, effective and reasonable correction measures were proposed for the site conditions. The results show that with the increase of loading time, the pile response distribution along the depth changed significantly, while the time-dependent lateral deformation of the soft soil caused by the surcharge load caused the lateral additional pressure acting on the pile side to gradually increase, but its distribution range along the depth remained unchanged and was mainly distributed in the depth range of the soft-weak soil layer. Based on the assessment of the ultimate bending moment in the pile sections, the pile foundation studied was still in a safe state, but extra attention should be paid to the bending moment at the location of the connection between the cap and the pile foundation and at the interface between the upper soft layer and the lower harder soil layer. In addition, the proposed corrective measure of unloading+high-pressure rotary pile reinforcement can achieve the expected correction effect.

Abstract:This analysis is based on relevant engineering cases in domestic and international contexts, the structural system of assembled bridge piers is introduced. The advantages and disadvantages of different types of assembled piers are analyzed and compared from the perspectives of structural stress performance, durability and construction convenience. Through analysis of the existing research results found that: most of the existing research focused on the seismic performance of the piers, but the research involving the compressive and shear performance of assembled RC piers is still relatively rare, Pacifications for Design of Highway Precast Concrete Bridges (JTG/T 3365-05—2022) although the structural calculation method of assembled concrete piers, but not yet according to the different types of assembled piers of the splicing structure characteristics, the corresponding limit of the local structure bearing capacity calculation method; Pacifications for Design of Highway Precast Concrete Bridges (JTG/T 3365-05—2022), Specifications for Construction of High Wary Precast Concrete Bridges (JTG/T 3654—2022) for some types of assembled piers construction requirements, construction techniques, some local standards have involved assembled piers seismic design, construction, acceptance, etc. These standards can be used to guide the design and construction of some types of assembled piers, but its content is still not comprehensive. On this basis, the shortcomings of assembled piers in structural design, construction, quality control and other aspects as well as the future development direction are proposed.

Abstract:Cement (sand) slurry in the concrete plays a dual role of gelation and lubrication, its dosage with concrete increase with the increase of fluidity requirements, the existing research shows that slurry can lead to volume stability of concrete problems and low degree of green environmental protection, but the aggregate gradation on the effect of reasonable dosage of slurry in the concrete research is still rare. The influence of coarse aggregate grading and mortar rheological features on the mortar coating thickness and mortar coating content of coarse aggregate is studied by adjusting the mortar content under the condition of equal slump-flow of concrete, which coarse aggregate has a fixed amount and relative less bulk voids. The mortar coating thickness increases monotonically with the increase of the geometric average particle size of coarse aggregate, mortar coating content shows a trend of first decreasing and then increasing, while a minimum mortar coating content occurs around the optimal geometric average particle size. It has also been proved that larger mortar coating thickness and mortar coating content are required with higher fluidity, but the smaller the optimal geometric mean particle size. The mortar coating thickness and mortar coating content increase with the increase of mortar yield stress and plastic viscosity under fixed particle size grading of coarse aggregate.

Abstract:Knowing the mechanical behavior of montmorillonite under tensile stress is crucial in earth sciences and geomechanics. However, existing theories and methods are difficult to predict its hydration mechanical properties and inner mechanism within the small layer-spacing. In this paper, through the stress-strain script, tensile molecular dynamics simulation and stress-strain analysis are conducted on montmorillonilte with different hydration amounts to determine the mechanical properties, interaction mechanism and microstructure evolution. It is found that the weakening effect of interlayer hydration on the ultimate stress and tensile modulus is obvious, and the weakening effect is larger in the early stage of hydration; the volume expansion with hydration results from the linear increase in lattice length c. The Z direction tensile modulus is much smaller than the in-plane, that is, the stress has the greatest influence on the mechanical behavior of surface Z direction; after reaching the ultimate tensile stress, the layer separation failure occurs; besides, the interlayer is the main cause of deformation and dominates the tensile mechanical properties of montmorillonite; the tensile stress in the Z direction causes the increase of lattice length c and lattice angle β, while in the X and Y directions, it is mainly the decrease and increase of β. The higher the layer charge density, the denser the bound-water film, the more hydrogen bonds formed, the smaller the volume and lattice length c, and the stronger the tensile mechanical properties.

Abstract:In order to investigate the mechanical properties of polyethylene fiber-reinforced engineered cementitious composites (PE-ECC) with rubber powder, static and impact resistance tests were carried out on the PE-ECC with varying parameters of rubber powder particle sizes and strain rates. Elastic modulus, Poisson,s ratio, cubic compressive strength, primal strength, splitting tensile strength, and axial tensile strength of the rubber powder PE-ECC were experimentally obtained, and the influence of rubber powder particle sizes on static mechanical properties of the PE-ECC were analyzed. The impact performance of the PE-ECC with rubber powder was evaluated using a split Hopkinson pressure bar, and the dynamic growth factor of strain rate on the dynamic impact factor (DIF), peak dynamic stress, and peak dynamic strain were analyzed. The experimental results indicate that the mechanical properties of the PE-ECC decreased with the usage of rubber powder. For the particle size of rubber powder ranged from 0.2 mm to 0.9 mm, the PE-ECC with particle sizes of 0.3 mm for rubber powder exhibited acceptable static and dynamic performance. Comparing to the PE-ECC without any rubbers, the cubic compressive strength, primal strength, elastic modulus, and dynamic compressive strength of the PE-ECC using 0.30 mm-particle size rubber powder and a volume content of 10% decreased by 8.9%, 15.6%, 10.8%, and 23.4%. Similar to the PE-ECC without rubber powder, the tensile strain hardening effect of rubber powder P-ECC was significant and the ultimate tensile strain of PE-ECC with different partial size (0.20-0.90 mm) rubber powder remained at 4.6%. Moreover, with the increase of impact strain rate, the DIF and dynamic compressive strength of rubber powder PE-ECC gradually increased.

Abstract:In order to improve the abrasion resistance of concrete, the effects of granular, acicular and powdered rubbers on the abrasion performance of concrete were studied. Based on granular rubber concrete, basalt fiber was added to study the abrasion performance of concrete when fiber-rubber composite was used. The microstructure was observed by SEM and the abrasion enhancement mechanism was analyzed. The fractal dimension was used to characterize the morphology change of concrete abrasion process, and the relationship between fractal dimension and abrasion degree was discussed. The results show that when 15% of granular rubber, acicular rubber and powdered rubber are added respectively, the abrasion resistance of concrete increases by 140.24%, 157.96% and 83.88%. When the basalt fiber content is 0.1%, the abrasion resistance of granular rubber concrete increases by 11.63%. Fiber and rubber can play a role at different levels and jointly enhance the abrasion resistance. The degree of concrete abrasion can be characterized by the fractal dimension. With the increase of time, the more serious the concrete abrasion is, the larger the fractal dimension is. The relationship between fractal dimension and mass loss rate and volume loss rate is obtained, and the curve equation is established.

Abstract:In order to to improve the pozzolanic activity of the pulverized powder from the high temperature sintering slag of surface treatment sludge and construction residue, the effect and mechanism of Ca(OH)₂ on mechanical properties and heavy metal leaching of Portland cement-based materials were studied, and the microstructure characteristics of the materials were analyzed by XRD, SEM, BET, TG and other microscopic testing techniques. The results show that when Ca(OH)₂ content is 0.6%~0.8% of the total mass of ground powder cement-based materials, the mechanical properties of cement-based materials mixed with grinding powder are better. At 60 days, the flexural strength and compressive strength increased by 11.0% and 7.8%, respectively. Microscopic test results show that a small amount of Ca(OH)₂ can not only increase the specific surface area of ground powder cement-based materials’ hardened slurry, but also increase the number of hydration products, and improve the structural compactness of hardened slurry. However, when the content of Ca(OH)₂ exceeds 0.8% of the total mass of cement-based hardened slurry, it has a negative effect on the structure and properties of cement-based materials. It is also found that the addition of Ca(OH)₂ can reduce the leaching concentration of harmful heavy metals in cement-based materials with the addition of the ground powder. The leaching rates of Cu, Ni and Zn were 17.5%, 13.0% and 40.8% lower than those of blank group. It can ensure that the leaching values of harmful heavy metals Cu, Ni, Zn and Cr in cement-based materials mixed with grinding powder are lower than the leaching concentration limits specified in the Technical Specification for Coprocessing of Solid Waste in Cement Kiln (GB/T 30760—2014).

Abstract:Industrial park wastewater treatment is an important step in reducing pollutants and improve the quality of water environment. Natural conditions, influent impact, diversity of pollutant composition and complexity of wastewater treatment technology lead to uncertainty and change of wastewater treatment system in industrial parks. These uncertainties lead to fluctuations in effluent quality and operating costs in industrial parks, as well as environmental risks in receiving water bodies. Artificial intelligence has become a powerful tool to reduce the complexity and risks of wastewater treatment. Through a large-scale bibliometric analysis of the application of artificial intelligence technology in wastewater treatment, this paper systematically reviews the application of artificial intelligence technology in five aspects of industrial park wastewater treatment, such as monitoring, pollutant removal, energy saving, management and wastewater reuse, and summarized the appropriate application scenarios, prediction accuracy and application limitations of typical artificial intelligence technology. Finally, we discuss potential future directions for utilizing the new research frontier of artificial intelligence in wastewater treatment plants, while addressing challenges of pollutant removal, cost reduction, water reuse and management in complex practical applications.

Abstract:Under the background of promoting environmental function quality and carbon peak and carbon neutrality, the hidden problems of repeated consumption and low sustainability in artificial nitrogen fixation/ nitrogen removal process come to prominence. Synthesizing the necessity and resource availability of ammonium-nitrogen in wastewater, research and development of ammonium-nitrogen resource recovery technology is receiving more and more attention in wastewater treatment. Among the existing techniques, electrochemical technology has become a hot research direction due to its advantages such as fast reaction, simple equipment, and convenient operation. In this paper, an overview of the research and development status of electrochemical-mediated ammonium recovery technology in recent years was reviewed. Focusing on the migration and conversion mechanism of different forms of ammonium-nitrogen in the electrochemical system, three main principles of recovery technology were introduced including electrochemical-driven migration and adsorption, cathode reaction-driven volatilization and anode reaction-driven precipitation. The enhancement effect of electrodes and membrane materials on the ammonium recovery performance was then highlighted and the energy efficiency of related processes including capacitive deionization and membrane-based processes (via cation-exchange membrane, gas-permeable membrane and bipolar membrane) was analyzed, leading to the conclusion that an integrated process toward ammonia recovery exhibits merits of low energy input and high removal/recovery efficiency. Finally, the inherent demand for technological innovation in a low-carbon background was discussed, the future efforts would hopefully be directed toward the development of high-performance system components, energy reduction, and functional expansion/smart operation to promote the high-quality and sustainable development of electrochemical-mediated ammonium recovery technology.

Abstract:In recent years, the demand for lithium-ion batteries (LIB) has grown rapidly, but many basic elements in the positive electrode, such as lithium, cobalt, and nickel, are expensive and heavily dependent on imports. At present, most hydrometallurgical leaching methods are based on the use of an “in/organic acid+H₂O₂” system, but there are environmental pollution, safety hazards, and efficiency issues. Therefore, this study proposes a new environmentally friendly, safe, and efficient leaching process using malonic acid and ascorbic acid as leaching and reducing agents. Under the optimal conditions: malonic acid concentration of 0.4 mol/L, ascorbic acid concentration of 0.2 mol/L, solid-liquid ratio of 30 g/L, leaching temperature of 50 ℃, and leaching time of 50 minutes; the leaching rates of lithium, nickel, cobalt, and manganese are all more than 95%. The kinetic fitting validation results indicate that the leaching process conforms to the “shrinking core model” and the apparent activation energy is lower than the previous values of “organic acid+H₂O₂”; therefore, the addition of ascorbic acid can effectively promote the leaching of valuable metals from positive electrode materials with malonic acid, thereby improving the leaching efficiency; the infrared spectrum and XRD results indicate that the coordination form between malonic acid and transition metals during the leaching process is C₃H₂O₄M (M is transition metals Ni, Co, Mn).

Abstract:Microbial fuel cells have already been used as biosensors to monitor assimilable organic carbon (AOC). However, their signal production from AOC is known to be completely suppressed by dissoved oxygen (DO). In this study, two identical microbial electrolysis cell (MEC) based biosensors were inoculated with marine sediment and operated at two different anodic potentials, namely -300 mV and +250 mV relative to Ag/AgCl. The MEC biosensor operated under positive anodic potential conditions had electrochemically active microbial communities on the anode, including members of the Shewanellaceae, Pseudoalteromonadaceae, and Clostridiaceae families. However, the strictly anaerobic members of the Desulfuromonadaceae, Desulfobulbaceae and Desulfobacteraceae families were found only in the negative anodic potential MEC biosensor. The positive anodic potential MEC biosensor showed several other advantages as well, such as faster start-up, significantly higher maximum current production, fivefold improvement in the AOC detection limit, and tolerance of low dissolved oxygen, compared to those obtained from the negative anodic potential MEC biosensor. The developed positive anodic potential MEC biosensor can thus be used as a real-time and inexpensive detector of AOC concentrations in high saline and low DO seawater.