Abstract:In recent years, extreme meteorological and hydrological events have become more frequent and intense, and the frequent occurrence of flood disasters in a rapidly evolving environment has brought severe challenges to socio-economic development. This study focuses on Chongqing, one of two principal cores within the megacities of western China, part of the Chengdu-Chongqing urban agglomeration. This city, s terrain, predominantly hilly and mountainous, together with its proximity to upstream rivers and the backwater of the Three Gorges Reservoir Area (TGRA), highlights its exposure to the threat of flood disasters. This study focuses on Chongqing, s historical flood disaster events to assess the current state of flood prevention and disaster reduction efforts within the city. The authors further analyze the impact of various factors, including hydrology, geography, topography, urbanization, and meteorological conditions, on both the frequency and intensity of flood disasters in Chongqing. Alongside these causal factors of flood disasters, the authors further delve into the analysis of Chongqing, s disasters—Forming environment and the entities that bear these disasters. Finally, countermeasures are provided. The findings indicate that the occurrence of flood disasters in Chongqing is influenced by various factors, and its special location and characteristics of the mountain city determine the difficulty of flood prevention and management in Chongqing. Notably, the city, s complex terrain and numerous rivers creat the conditions conducive to flood disasters. Given the evolving circumstances brought about by meteorological hydrology and socio-economic development, it is imperative to proactively reassess and optimize Chongqing, s urban flood disaster prevention system. This should be done in accordance with the unique flood disaster characteristics that have emerged following the completion of the TGRA and the current flood control and waterlogging prevention capacity of the urban area.

Abstract:When the slurry shield passes through the composite formation, the parameters of shield tunneling control and slurry separation system generally fluctuate greatly, influencing construction safety and tunnelling efficiency. In order to improve the safety and stability of the construction process and prevent abnormal working condition prediction, based on the Wangjing Tunnel, the coordinated control technique, including solid-liquid separation screening, two-stage cyclone, and centrifugal /pressure filtration are adopted according to the stratum conditions. Shield tunneling parameters (tunnelling speed, cutter head speed, total propulsion force, etc.) and slurry separation parameters (feed quantity, feed gravity, feed viscosity, etc) are collected. Data quality can be improved through Cook distance outlier detection, wavelet threshold denoising. 12 parameters are selected as inputs, such as specific gravity ratio and viscosity ratio of two-stage cyclone separation, and the output parameters are discharge volume, discharge specific gravity and discharge viscosity，A BP neural network was established to predict parameters of the slurry separation system, three different formation annulus were selected for prediction. Results show that the average prediction errors are all within 5%, while predictions have high accuracy under the composite formation.

Abstract:To address the issue of decreased heat and vacuum negative pressure in soil, which leads to uneven reinforcement effect during vacuum thermal consolidation, the vacuum thermal consolidation combined with dynamic compaction method is applied for engineering waste slurry treatment, and the characteristics of soil compactness can be improved by dynamic compaction method. The influence of different tamping times on the reinforcement effect of soil was studied through four groups of model tests. Results show that when the settlement rate is 4 cm/(3 d), the tamping time is the best, the settlement of soil surface is 26.55%, 11.72% and 3.74% higher than that of other tests correspondingly, and the treatment effect of engineering waste slurry is the best, effectively solving the unsatisfactory reinforcement effect of deep soil under vacuum thermal consolidation and improve the uniformity of soil. Combined with the results of microstructure analysis, it can be found that due to the redistribution of pores between soil particles, the soil density is higher, and the shear strength of the cross plate increases accordingly under the appropriate tamping time. In addition, the drainage channels formed by the micro-cracks generated by the redistribution of internal pores can promote drainage and further improve the consolidation effect. Therefore, the shear strength of the cross plate and degree of consolidation of the soil can be enhanced under the appropriate tamping time.

Abstract:After flocculation conditioning and chemical solidification, the engineering characteristics of high-water-content mud can be improved. If waste mud is to be recycled into embankment filler, it is bound to have certain requirements on the strength of the treated mud. In recent years, the authors have explored and proved that the vacuum preloading-flocculation-solidification combined method (VP-FSCM) can effectively treat mud slurry with high water content (>300%), and the strength of the treated mud can meet the demand for embankment filler utilization. This study has carried out a series of laboratory model tests to explore the feasibility and high efficiency of VP-FSCM process for treating waste mud (water content is about 150%-300%); and to optimize the formulation (type, dosage, etc.) of VP-FSCM process in waste mud treatment. The test results show that: (1) The undrained shear strength of the waste mud treated by VP-FSCM after 28 days is 2.76 times that of the waste mud treated by the flocculation-solidification combined method (FSCM), which proves the high efficiency and feasibility of VP-FSCM. (2) The results of dehydration / settlement characteristics and mechanical characteristics show that the optimal additives for treating waste mud by VP-FSCM process are cement (OPC), ground granulated blastfurnace slag (GGBS), quicklime (CaO) and polyacrylamide (PAM), and their optimal contents are 5%, 5%, 1.5% and 0.12% respectively. (3) Under the optimal additive type and dosage, higher vacuum pressure results in greater undrained shear strength of the treated waste mud and lower moisture content after curing.

Abstract:In order to find out the influence of screw height on bearing characteristics of threaded pile and soil around the pile under vertical loading, this paper studied the influence of different screw heights on the bearing performance of pile, soil failure characteristics around the pile and soil displacement field around the pile through laboratory half-surface model pile test combined with digital image correlation (DIC) technique. The ABAQUS numerical simulation method was used to validate the results of the model test, and the range of screw height values was extended. The pattern of the ultimate bearing capacity and material utilization rate of threaded pile as well as the distribution of soil stress field around the pile were analyzed. The results show that the utilization bearing capacity of pile is increased, the influential zone of the soil displacement around the pile gradually increased and the development of shear failure of soil around the pile can be delayed with increase of the screw height. As the settlement of the pile body increases, the loading on the pile top gradually evolves from being borne by the pile side resistance to borne by the pile end resistance. Although increasing the screw height can enhance the ultimate bearing capacity of pile, there is a peak in the material utilization rate of the pile.

Abstract:A sandy soil liquefaction interlayer can cause both foundation failure and damping effects on the superstructure, while the overburden would reduce building settlement but increase seismic effects. Therefore, it is necessary to consider the seismic coupling effects of the liquefied interlayer and the overburden on the building under the structure-soil interaction. Based on the Biot two-phase saturated porous medium dynamic coupling theory, the effects of seismic intensity, sand compactness D_r and liquefied layer thickness-to-depth ratio K (considering the coupling effect of liquefied interlayer and overburden) on the seismic isolation of the superstructure are analysed using finite element and finite difference coupled dynamic analysis methods. The results show that the structural acceleration spectrum ratio first decreases and then stabilises with increasing seismic intensity, and the damping effect of the liquefied layer no longer increases when the seismic intensity exceeds a certain threshold; the damping effect of loose sand (D_r=30%) is better than that of medium-density sand (D_r=50%) and dense sand (D_r=70%), but it would cause a non-negligible settlement hazard, while dense sand, although it will better suppress the settlement amount of the building, would lead to amplification of vibration; considering the coupling effect of overburden and liquefied layer, it is found that there is a K-value interval (0.3<K<0.5), which can both reduce building settlement and act as shock absorber.

Abstract:Laying a flexible cushion or backfilling lightweight soil behind the retaining wall has important engineering significance for its optimized design and cost reduction. By carrying out model tests of retaining walls under different level of loads, the magnitude and distribution characteristics of the lateral earth pressure when laying EPS flexible cushion, backfilling lightweight soil and applying it simultaneously are analyzed, and the load-reducing effect is discussed. The result shows: when the retaining wall is paved with flexible cushion, backfilled with lightweight soil, or both applied, the lateral earth pressure exhibits a “bulging” nonlinear feature that increases first and then decreases with the burial depth, and the maximum value of earth pressure generally appears at half of the wall height; under the same loading, the load-reducing effect of backfilling lightweight soil is relatively weak, achieving a reduction rate of 10%-25%, the maximum load-reducing rate of laying a flexible cushion is increased by 1.5 times compared with lightweight soil, when both are applied, the load-reducing effect is the most significant, and the maximum load-reducing rate is increased by nearly 3 times; the load-reducing effect of the flexible cushion decreases with the variation of thickness, the foam content is more sensitive to the load-reducing rate of the backfill lightweight soil. In the engineering project, a medium-thickness cushion is an optimal choice, if the applied load of the backfill is large, the content of the backfill lightweight soil can be appropriately increased.

Abstract:Based on tunnel boring machine (TBM) disc cutter penetration laboratory model tests, the penetration load evolution characteristics of high-strength granite specimens under different confining pressures were studied using three different rock-breaking modes (intact rock-breaking, rock breaking along pre-cutting trajectory and rock breaking between pre-cutting trajectory). The study focused on revealing the penetration load-penetration depth characteristic curves, peak load, maximum drop amplitude variation laws, and obtaining the force characteristics of TBM disc cutters under different rock-breaking modes and confining pressures. The results show that: (1) The penetration load-penetration depth characteristic curve of the high confining pressure group drops earlier and has a smaller decrease in amplitude than that of the low confining pressure group, but the corresponding penetration load is not the peak load, while the initial drop load of the low confining pressure group is the peak load, and the drop amplitude is larger; (2) The peak load and the maximum drop amplitude of the penetration load are smallest at medium-high confining pressures of 10-15 MPa, indicating that this confining pressure range is more conducive to TBM excavation; (3) Under low confining pressure conditions, choosing rock-breaking between pre-cutting trajectory mode can reduce TBM disc cutter penetration load more effectively than rock-breaking along pre-cutting trajectory mode. However, the rock sample with the rock-breaking along pre-cutting trajectory mode exhibits wedge failure, and its maximum drop amplitude is the smallest, which can reduce the impact load on cutters and reduce cutter wear.

Abstract:The excessive number of cementing solution injections required for MICP limits its practical engineering application. In order to reduce the number of injections and improve the efficiency of the cementing process, an enhancement method was investigated in this study in which aluminum ion flocculant was added to the cementing solution to enhance the curing rate and effectiveness of MICP. Experiments were carried out on MICP-reinforced sand columns, and the influence of different concentrations of AlCl₃?6H₂O on the cementing solution was studied. Then the influence of AlCl₃?6H₂O on production of calcium carbonate and unconfined compressive strength (UCS) was studied. In the aqueous solution test, the changes of precipitation and solution pH under different solution conditions were observed, and the effects of the aluminum ion flocculant on the composition and morphology of the deposited calcium carbonate were investigated using XRD and SEM tests. The results show that, compared with the control group, after adding an appropriate amount of aluminum ion flocculant to the cementing solution, the proposed method resulted in the experimental sand column being reinforced after 3 treatments of the cementing solution. The UCS reaches 1.7 MPa after 5 treatments of the cementing solution, compared to 9 treatments using the conventional method. The addition of AlCl₃?6H₂O to the cementing solution significantly reduced the number of MICP injections required compared to the control group. This study provides an important reference for applying MICP-reinforced sand in practical engineering.

Abstract:In order to study the adsorption characteristics of water vapor on unsaturated loess, isothermal adsorption experiments under different humidity conditions were carried out by vapor equilibrium method. The adsorption behavior of water vapor on the surface of unsaturated loesswas analyzed, and the effects of temperature, mineral composition and content, dry density on the adsorption property of soil were discussed. The experimental results show that the water vapor adsorption capacity of unsaturated loess increases with the increase of relative humidity, and the entire process consists of three stages: monolayer adsorption, multilayer adsorption and capillary condensation. The GAB model can describe the water vapor adsorption process of unsaturated loess. There is a significant negative correlation between water vapor adsorption capacity and temperature. When the relative humidity is constant, the adsorption capacity of water vapor decreases with the increase of temperature. Water vapor adsorption of unsaturated loess is closely related to mineral composition, and clay mineral content directly affects its water vapor adsorption capacity. In addition, the effect of dry density on water vapor adsorption capacity can be divided into two stages. When the relative humidity RH<80%, water vapor adsorption capacity increases with the increase of dry density. For capillary condensation stage, with the increase of dry density, the amount of water vapor adsorption no longer increases but decreases.

Abstract:Industrial solid waste phosphogypsum and lignin were used to solidify the artificially formulated lead contaminated soil. Through the unconfined compressive strength (UCS) test, the effect of curing agent dosage and curing age on the stress-strain curve, failure pattern and UCS of the soil with different levels of lead contamination after solidification were investigated, and the curing effects of the two curing agents were compared and analyzed. The microscopic characteristics of soil samples before and after curing were analyzed by scanning electron microscopy (SEM) test. The results show that both phosphogypsum and lignin can increase the UCS of stabilized soil and reduce the failure strain. UCS of solidified soil increases continuously with the increase of phosphogypsum content, and increases first and then decreases with the increase of lignin content. Extended curing time can effectively improve the UCS of stabilized soil. With the increase of dosage and curing age, the internal cementation level of soil increases, and the failure pattern of soil sample gradually changes from local tension cracking to shear failure, showing brittle failure characteristics. The two curing agents have their own advantages and disadvantages in curing soil. Lignin is more effective than phosphogypsum in curing high concentration lead contaminated soil and has better resistance to deformation, while phosphogypsum has better ability to improve strength and fix lead in a short time. SEM tests show that the curing agent can fill the pores and cement soil particles, and the hydration products form a dense structure in the soil, which is macroscopically expressed as strength enhancement.

Abstract:To dispose of sludge and construction waste and facilitate their common resource utilization, the solidification tests of sludge are carried out in the laboratory and in site. In the field test, the construction waste is used as aggregate and added to the sludge by 15% of the mass ratio of the sludge, and then the sludge solidified agent is added to the sludge. Sludge, construction waste and solidified agent are mixed evenly by mechanical stirring, and finally the solidified soil is cured. The laboratory test results show that when the content of solidified agent is 8%, the strength of solidified sludge is quite high, and the laboratory UCS of solidified sludge can reach 320 kPa after curing for 28 days. The cone penetration test and plate loading test in field show that the solidified agent has an obvious solidifying effect on sludge. With low dose solidified agent, the structure effect of aggregate is not obvious. When the content of solidified agent is 8%, the structure effect of aggregate is beneficial in improving the bearing capacity of solidified sludge and the characteristic soil bearing capacity can reach 325 kPa. The improvement rate of solidified sludge by structure effect is 71.05%, which facilitates the common resource utilization of silt and construction waste.

Abstract:Most of the existing ancient buildings are in service with injuries, and the internal damage state is complex and diverse. Meanwhile, the reinforcement and maintenance of the ancient buildings carried out by the later generations and the original damage have the opposite impact on the safety performance of the original structure. In order to realize the preventive protection of ancient buildings, it is necessary to quantify the impact of damaged state and repair measures of pure wooden structures on the safety state of ancient buildings. Based on the statistical data of the damaged state of various components of Feiyun Wood Pavilion in Wanrong, Shanxi Province, and combined with existing norms and engineering experience, this paper divides the damaged state of components in detail, establishes a four-level fuzzy hierarchical analysis model, and determines the weight value and judgment matrix of the load-bearing components and the damage types of components in the structure. The security state of Feiyun Wood Pavilion is evaluated by fuzzy analytical hierarchical approach. The results show that the fuzzy analytical hierarchy safety evaluation model established can reflect the damage state and the impact of repair measures on the safety state of Feiyun Wood Pavilion, effectively link structural evaluation with the component evaluation, and verify that the repair measures can effectively enhance the safety and stability of the ancient building structure. The model and method can be applied to the safety grade evaluation of multi-storey ancient wooden structures.

Abstract:The shear failure mode and failure mechanism of 12 CFRP-strengthened concrete beams without stirrups were analyzed. The stress-strain curves of the CFRP beams in the whole process were obtained. The quantitative effects of structural size and CFRP ratio on the shear strength of CFRP are discussed. Furthermore, a formula for calculating the shear strength of CFRP is proposed and compared with the test results, the test results of others and the standard results in this work. It is found that the structural size has a significant influence on the shear strength of CFRP. The nominal shear strength of CFRP decreases significantly when the structural size increases. In addition, when the beam depth changes from 300 mm to 1 200 mm, the nominal shear strength of CFRP decreases by about 50%, which has an obvious size effect. Furthermore, under different cross-section sizes, the nominal shear strength of CFRP increases with the increase of CFRP ratio ρf , but with the increase of CFRP ratio ρf, the increase amplitude of nominal shear strength decreases, showing a nonlinear growth trend. Finally, the established formula for calculating the shear capacity of CFRP could predict the shear capacity of CFRP under different CFRP ratio and section size scientifically.

Abstract:Until now, there has been limited research on the bonding behavior of ribbed fiber-reinforced polymer (FRP) bars. In this paper, bond test data of the spirally-glued FRP bar and mechanically-grooved FRP bar were collected to investigate the test parameters on the bond behavior. The results show that the macroscopic failure mode for the two types of ribbed FRP bars is pullout failure. More specifically, spirally-glued FRP bars mainly exhibit shearing off of FRP bar ribs, while slight damage occurs in concrete. Most grooved FRP bars show shearing off of concrete ribs, and the bond strength increases with the increase of concrete strength for both FRP bars. Spirally-glued FRP bars show higher bond strength by increasing concrete cover which contributes to better confinement to FRP bars, but this seems to have no effect on grooved FRP bars. The bond strength of spirally-glued FRP bars can be improved by increasing relative rib height h_rd and FRP bar rib width ratio F_R. While grooved FRP bars are almost unaffected by h_rd, and are mainly influenced by concrete rib width ratio C_R, having higher bond strength by increasing C_R. The calculated results by the proposed equations are in good agreement with the test results with greater accuracy than the design codes. This is because the effect of rib forming process and geometrical features of ribbed FRP bars on bond strength is accurately accounted in the proposed equations.

Abstract:Welded detail is the weak part of steel bridges. The fatigue damage of the welded joint is becoming one of key problems affecting the service safety of bridges under repeated vehicle loads. This study conducted static tensile and fatigue crack growth (FCG) tests of the base metal and weld joint of Q550E high strength steel. The FCG models of base metal and welded joint were established, and the effects of stress ratio on the FCG rate of welded joints of high strength steel were revealed. The coupled simulation method of FRANC3D and ABAQUS was performed, and the key influence parameters were determined by sensitivity analysis. The results show that the FCG rate parameter m increases with the increase of stress ratio. The FCG rate parameter lg C and the threshold stress intensity factor range decreases. The parameter m of butt weld specimen is about twice that of base steel. The threshold stress intensity factor range of weld joint is larger than the base steel and more sensitive to the stress ratio. The developed coupled simulation method can accurately predict the fatigue life of high strength steel welded joints. The specimen thickness and initial crack depth have a significant impact on the fatigue growth under high stress ratio.

Abstract:A novel design method for concrete-filled square steel tubular spliced columns with grouting anchor connections is proposed in this paper to increase the assembly efficiency, improve the seismic performance and reduce production cost of the column members in the steel-concrete composite structures. The seismic performances of novel spliced columns with different reinforcement ratios, reinforcement configurations and column-column joint positions were tested via quasi-static loading test on five spliced columns and one monolithic cast column with a scale ratio of 2. The results showed that the failure modes and processes of the novel spliced column members under low cyclic loading are similar to those of the reference member. The hysteretic curves of the novel spliced columns are full, and the energy dissipation capacity, load bearing capacity degradation and stiffness were advantageous than those of the reference column member. In particular, the P-type members with the column-column joint located in the column inflection point area had better ductility and deformation capacity under the seismic effect. The test results identify that the novel spliced columns designed method proposed is scientific and has application potential to improve the overall seismic performance of the steel-concrete composite frame structures.

Abstract:In recent years, deep neural network and computer vision techniques have played an increasingly important role in structural health monitoring. In this paper, deep learning technology is used to identify the PE sheath damage through the image data of bridge stay cable damage collected by UAV. This paper aims to realize the intelligent and rapid identification of local damage on the surface of stay cables of long-span bridges on devices with low computational ability, and to solve the problems of relatively low computational efficiency and large scale of model parameters in the current research of traditional deep convolution neural network. A lightweight region proposal convolution neural network model is proposed. Firstly, the theoretical basis of region proposal network and its lightweight improvement method is introduced, and the necessity of lightweight model processing is analyzed. It reduces the performance requirements of devices for model training and prediction under the premise of ensuring identification accuracy, achieving the purpose of saving computational resources and time. Secondly, the problem of insufficient data of damage samples is solved by multiple means of data augmentation. The contrast experiment and the analysis of statistical results verify the superiority of the lightweight neural network model. The results show that the lightweight network can improve the complexity and quantity of calculation of the model to a large extent under the premise of a small sacrifice of recognition accuracy. It effectively expands the practicability of the neural network in engineering applications.

Abstract:In order to study the splitting tensile failure characteristics of ultra-high performance concrete (UHPC), three different loading rates (0.1, 0.01, 0.001 mm/s) were used for the splitting tensile loading. During the loading process, the digital image correlation (DIC) method was used to observe the crack evolution by non-contact deformation. At the same time, the acoustic emission (AE) technology was used to dynamically monitor the entire failure process of UHPC, and the failure characteristics of the specimen were analyzed based on the DIC strain cloud map and AE parameters. The results show that due to the incorporation of steel fibers, the brittleness of concrete is improved, and the post-peak load-displacement curve of UHPC decreases more gently without a sharp decline. The higher the loading rate, the higher the splitting tensile strength measured by UHPC, which conforms to the law of concrete rate effect. When the loading rate is increased from 0.001 mm/s to 0.01 mm/s and from 0.01 mm/s to 0.1 mm/s, the splitting tensile peak load is increased by 27.9 % and 28.5 % respectively. The digital image correlation method is used to measure the deformation of UHPC splitting tensile experiment, and continuous deformation data can be obtained, which can completely capture the development process of cracks. It is proved that DIC can well reflect the evolution process of cracks on the surface of specimens. The analysis based on RA-AF value can quickly and effectively determine the type of crack development in concrete. According to the analysis results, the crack types of UHPC splitting tensile experiment are mostly tensile cracks, and the proportion of tensile cracks in the total cracks increases with the increase of loading rate.

Abstract:Alkali slag recycled concrete is a new type of concrete prepared by replacing cement with alkali excited cementing material and natural stone with recycled aggregate, which can effectively reduce the amount of Portland cement and improve the utilization rate of waste concrete. However, there has been no relevant research on its mechanical properties. In order to study the basic mechanical properties of alkali slag recycled concrete, the compression test, splitting tensile test and flexure test were carried out with the steel fiber replacement rate and the recycled aggregate replacement rate as the main test parameters.The results show that: With the increase of recycled aggregate, the cube strength f_cu, splitting tensile strength f_t and flexural strength f_w of recycled alkali slag concrete all decrease, and the reduction range is 30%, 10% and 15% respectively when the substitution rate of recycled coarse aggregate is 100%. The cube strength and splitting tensile strength of alkali-slag recycled coarse aggregate concrete with increase first and then decrease with the increase of steel fiber volume substitution rate. When the steel fiber volume substitution rate is 0.6%, the compressive strength and flexural strength reach the maximum value. The flexural strength of alkali slag recycled concrete increases with the increase of steel fiber volume substitution rate.

Abstract:To investigate the micro-cracking evolution mechanism of cement stabilized macadam, a numerical model of mesoscale heterogeneous cement stabilized macadam was established. The microfracture network was introduced into the fine-scale inhomogeneous model and the relevant parameters were obtained using unconfined compressive strength tests. Then, the effect of different microfracture parameters on the micro-cracking degree was explored according to the displacement variation of particles in the model under vibration load. Finally, the energy evolution law of the system with different microfracture numbers was further analyzed. The results indicate that the numerical simulation results are in good agreement with the laboratory test results, the discrete element model of cement stabilized macadam can accurately characterize the mesoscopic failure characteristics of materials. Micro-cracking damage after the secondary vibration load together with the increase of microfracture width and microfracture number as a result. The microfracture density plays a decisive role in the degree of microcrack for cement stabilized macadam. With the increase of the microfracture number, the elastic strain energy storage capacity of the material decreases, and the total energy input of the cement stabilized macadam decreases. This study has proved that the positive effect of early micro-cracking on shrinkage stress reduction. In addition, the mechanical characteristics and fine mechanism of micro-cracking in cement stabilized macadam materials are revealed.

Abstract:There has been an increasing focus on the effective utilization of secondary resources and the prevention and mitigation of environmental pollution. Aluminum dross, recognized as a potential secondary resource due to its abundant reserves, has garnered significant attention for its resource utilization potential. The utilization of aluminum dross in the production of water treatment coagulants, through rational resource allocation, not only facilitates resource conservation and cost reduction, but also addresses the challenge of harmless aluminum dross treatment. The paper summarized the important raw material (calcium aluminate) and five types of aluminum ash-based coagulants (aluminum sulfate, polyaluminum sulfate, polyaluminum chloride, polyaluminum ferric sulfate, and polyaluminum chloride) used in the preparation of aluminum-based coagulants, along with their characteristics, preparation methods, and research progress. Furthermore, challenges were highlighted regarding the large-scale application of aluminumdross-based coagulants, necessitating a strategic approach focused on enhancing product competitiveness and addressing policy gaps. This aims to achieve high-quality, environmentally friendly, and sustainable development in the water treatment and aluminum industries, resulting in significant economic and environmental benefits.

Abstract:The UV/Fe(Ⅲ) process is a new combined process for treating heavy metal complexes. This process first releases free metal ions through the replacement of Fe(Ⅲ), then, it degraded the organic ligands via UV irradiation, and finally, heavy metals were removed by alkaline precipitation. In this study, heavy metal complexes, Cu(Ⅱ)-EDTA and Ni(Ⅱ)-EDTA, were removed by UV/Fe(Ⅲ) process. Through the comparison of removal effects and mechanism analysis, the internal mechanism of the difference in removal effects of the combined process was described, and the corresponding optimization scheme was proposed. The results showed that the removal efficiency of Cu(Ⅱ)-EDTA and Ni(Ⅱ)-EDTA was quite different, and the removal rates of Cu and Ni were 70% and 41%, respectively. The main reason for the difference in removal efficiency between Cu(Ⅱ)-EDTA and Ni(II)-EDTA was determined through high-performance liquid chromatography (HPLC), spectrophotometric analysis, and benzoic acid (BA) probe experiments, showing that Fe(Ⅲ) had a noticeable difference in displacing Cu(Ⅱ) and Ni(Ⅱ), with replacement rates of 85% and 22%, respectively. Optimal Fe(Ⅲ) dosages and reaction temperatures were separately optimized for the Ni(Ⅱ)-EDTA replacement process. The results showed that the reaction temperature optimization can significantly improve the Fe(Ⅲ) displacement efficiency on Ni(Ⅱ)-EDTA. When the reaction temperature was increased to 35 ℃, the removal efficiency of Ni was increased from 41% to 60%. The reaction temperature is very important for the removal of Ni(Ⅱ)-EDTA by UV/Fe(Ⅲ) process, proper heating is helpful to increase the replacement rate and further improve the removal efficiency.

Abstract:Ultraviolet disinfection technology has attracted more and more attention due to its advantages of no need to add chemicals, broad-spectrum disinfection and less disinfection by-products. However, it is difficult to guarantee the disinfection effect caused by the fouling of quartz sleeves, which has become a bottleneck restricting the development of ultraviolet disinfection technology. In this study, a pilot test device was set up in the ultraviolet disinfection channel of the sewage plant, and ultrasonic waves were used to inhibit the fouling of quartz sleeves. Single factor experiments have determined that the appropriate ranges of ultrasonic power, cleaning cycle, and ultrasonic time are 500-1 000 W, 0.5-1.0 d, and 20-40 min respectively; For quartz sleeves with a service time of 0, 0.5, 1, 3, and 5 years, ultrasonic waves have a good fouling inhibition effect. In order to further optimize the parameters, the Box-Behnken design method and the response surface analysis method were used to optimize the main factors, and the response surface regression model and the optimal solution were obtained. The results show that the optimized process parameters of ultrasonic technology for fouling inhibition and cleaning are ultrasonic power P=965 W, cleaning cycle T=0.5 days, ultrasonic time t=34 minutes, and the maximum predicted relative ultraviolet intensity is 1.01. Through the statistical test, the model has a good fit, and the predicted value of the relative ultraviolet intensity obtained under the optimized process conditions is close to the experimental value with an error of 1.00%.