Abstract:The negative skin friction(NSF) has important influence on the bearing and deformation behavior of piles in collapsible loess soils. The current calculating method of NSF recommended by the Standard for Building Construction in Collapsible Loess Regions (Standard I) and the Technical Code for Building Pile Foundations (Standard II) cannot reflect the actual behavior of the NSF. This paper conducted a statistical analysis on the field flooding test datum of reinforced concrete piles in the loess area of China during the past 30 years. The relationship between the depth of the neutral plane, the depth of the maximum NSF as well as the coefficient of NSF with the pile length diameter ratio was analyzed, and the empirical expressions of the three parameters above with the pile length diameter ratio were obtained linear fitting, then a new approach for calculating NSF of piles in loess soils was established. According to the proposed method, the distribution of the NSF along pile shaft is represented by a triangle, i.e., the NSF increases with the depth and reaches a maximum value at a certain depth, then decreases to zero at the neutral plane depth, which perfectly reflects the actual distribution characteristics of the NSF along pile shaft. The calculated NSF by using the new method presented herein, Standard I and Standard II were compared with the field test datum. The results show that the neutral plane depth ratio predicted by Standard II is better than that by Standard I, and the maximum drag load predicted by Standard I is better, while the NSF calculated by the new approach are in good agreement with the measured.

Abstract:Based on Bockingham π theorem, a shaking table model test is carried out for the bedding rock slope with building pile foundation. Strain value of building pile foundation and the acceleration of the slope top, the seismic dynamic response of the system is studied base on the presstressed anchor cable. The results indicate that the strain of the anchor cable changes with the seismic wave, and the strain of the anchor cable reaches the maximum when the seismic wave reaches the peak, indicating that the upper cable force is larger than the lower. When the seismic amplitude increases, the upper anchor cable slips, and the anchoring effect decreases. The maximum strain of building pile foundation is located at a certain depth below the sliding surface, and the stress of building pile foundation far away from the slope is greater than that near the slope. The peak accelerations of slope top increase linearly with the seismic amplitude, but under the condition of Wenchuan-Wolong wave (0.55g) amplitude and Sin wave (0.4g) amplitude, there is a decreasing tendency among the peak acceleration at each point. With increase of seismic amplitude, the peak acceleration amplification coefficient of each point under Wenchuan and Sin earthquake does not change monotonously, but decreases first, and then increases.

Abstract:Slope soil erosion is common in hilly regions and reservoir bank slopes, as the primary driving force is brought by the thin overland water flow caused by rainfall or wave run-up, which results in the shear force and subsequently the incipient motion of soil. In order to explore the incipient motion conditions of slope soil under waterflow scouring, the incipient motion test and theoretical research of slope soil were carried out via self-developed testing device. The incipient motion phenomenon of cohesionless soil particles was observed by particle staining and high magnification electron microscopy, and the relationship between incipient motion mode of cohesionless bank slope soil and flow velocity was determined. This study also explored the relationships among differing dry densities, clay contents, and slopes with the critical incipient motion velocity on a clay slope, the results showed that clay content, dry density, and soil gradient had a great impact on the incipient velocity. Compared with the dry density and gradient, clay content had a clearer impact on incipient velocity. The incipient motion velocity equation of cohesionless bank slope soil was verified, and the rolling incipient motion velocity equation was reliable. The incipient motion mode of clay was used to establish the mechanical balance equation of the clay slope. Then, a semi-empirical incipient motion velocity equation of the clay slope was deduced, of which the relevant parameters were solved using the test results. The proposed incipient motion velocity equation showed good fit with the test results, and the verification results demonstrate that the equation is reliable.

Abstract:In order to study the influence of size effect of square foundation pit on the supporting effect of long and short pile retaining structure, numerical simulation is adopted for analysis of foundation pit of a bridge cap. Firstly, the selected parameters are verified by field measurement and the calculation conditions of different plane sizes are proposed, the size effect is analyzed by the change of stratum stress and soil pressure behind piles. Then, by comparing the deformation and stress of the long-short pile retaining structure and the equal-length pile retaining structure, the influence of the size effect on the supporting effect of the long-short pile retaining structure is examined. The main conclusions arrived at include: When the size of the square foundation pit is small, a continuous and closed “quasi-circular” arching area would be formed at a certain distance from the pit edge, and there is a “quasi-circular hoop effect” similar to the hoop effect in the circular foundation pit. When the arch area is closed as ring hoop, the earth pressure behind the retaining structure pile is significantly reduced. Otherwise, the earth pressure increases, and the increment of the earth pressure behind the pile in the middle of the pit is greater than that at the corner. The supporting effect of the long-short pile retaining structure is less in the square foundation pit with stronger size effect. The size effect of foundation pit is beneficial to its deformation and stability. In this project, the foundation pit with a side length of less than or equal to 14.4 m can make full use of the size effect and use long and short piles instead of equal-length piles for green environmental protection.

Abstract:The subway stations - bridge unitized (station - bridge unitized) projects can reduce urban traffic congestion and save construction space. But their seismic response mechanism and the seismic response of underground structures are not very clear. 3D models of station - bridge unitized condition and single station condition were established using finite difference software. Firstly, static calculations were completed, and the law of force and deformation of two conditions were analyzed. On the basis, with the input of El-Centro and Kobe waves, interlayer displacement angle, stress and weak positions of subway station were analyzed. Finally, the effects of load and height of the bridge on the seismic response of subway station were studied. The results indicate that as the input acceleration of bedrock increases, the effect of the overpass on the interlayer displacement angle and maximum stress of the subway station becomes greater. Tensile damage at the ends of station floors is easier to occur in station - bridge unitized condition, and the middle columns should also be attached equal importance to in strong earthquakes. There is a positive linear correlation between the interlayer displacement angle and bridge load, which can also be observed in bridge height. In addition, stresses increase linearly with bridge load and height.

Abstract:Bolt support is a common means in tunnel construction, and with the increasing working condition complexity, the combined structure of bolt and surrounding rock is also subjected to various dynamic loadings. In the past, researches focused on the mechanical characteristics of single bolt in tunnel, but there are few on the dynamic characteristics of the combination of bolt and surrounding rock. In this paper, the overall analysis of the bolt-surrounding rock structure, with a simplified roadway roof bolt-supporting model, combined with the dynamic double beam theory, was established to solve the dynamic model equation; MATLAB was used for numerical simulation to study the natural vibration characteristics of the structure under different supporting parameters and the dynamic response under the external load, and the vibration reduction measures were proposed. Finally, GTS NX is used to verify the safety of the supporting system. The results show that the dynamic characteristics of rock bolt-surrounding rock structure are related to the length of anchor segment, the distance between bolts and the diameter of bolts. In the model established in this paper, the dynamic response of the structure decreases obviously with the proper increase of anchorage length and bolt spacing. With change of bolt diameter, the dynamic characteristics of the structure are becoming complicated, and the dynamic response of different parts of the structure varies greatly.

Abstract:Evaluation of swelling behavior is of great importance for designing structures in expansive soils areas. Due to infiltration, the expansive soil produces swelling deformation in both vertical and horizontal directions, and the swelling pressure occurs if the swelling deformation was restrained that influences the stability of surrounding structures. In order to reveal the causes of anisotropy behavior of expansive soil in the process of wetting and swelling, from the microscopic point of view, this paper observed the microstructure of expansive soil from Baise with medium swelling potential and Zhijiang with weak swelling potential respectively, and statistically analyzed the orientated distribution of clay mineral particles in expansive soil by image processing technique. Meanwhile, from macroscopic aspect, variations of swelling strain with swelling pressure were measured under lateral confining condition via the developed 2D dilatometer and the modified specimen preparation method. The results show that the microstructure of expansive soil is flaky and stacked layer by layer. When the expansive soil is of natural loose state, the clay mineral particles are randomly oriented and aggregated; After compaction, clay mineral particles tend to be horizontally oriented due to the anisotropic stress. The higher the dry density, the denser the soil sample, and the more obvious its horizontal orientation. Under lateral confined condition, significant swelling differences are observed between the vertical and horizontal direction. The greater the dry density, the stronger the swelling capacity, and the more obvious the difference. However, for clay mineral particles, the swelling direction is perpendicular to their long axis, so the highly horizontal orientation is the reason why expansive soil shows swelling anisotropy behavior in macroscopic view. The swelling anisotropy is influenced by dry density and swelling ability, which is difficult to estimate, therefore it is suggested to measure the swelling principle in two directions in engineering practice.

Abstract:The composite early strength soil stabilizer (CRSS) has the characteristics of rapid setting and high strength. The independently developed CRSS stabilizer is used to rapidly solidify the surface sludge as the overlying hard shell layer. Through model tests, the failure mode of the hard shell layer, p-s curve characteristics, the shape of the deflection basin and the distribution law of soil pressure under different overlying hard shell layer thicknesses (3 cm, 6 cm, 9 cm and 12 cm) are studied. On the basis of the existing deformation theory of the deflection basin, combined with the test results, deformation shape function of the deflection basin is modified. The results show that with increase of the thickness of the hard shell, the failure mode of the hard shell transits from folding failure to punching failure; The greater the thickness of the hard shell, the more obvious the diffusion effect, and the higher the ultimate bearing capacity, as well as the corresponding increase in settlement; the settlement displacement at different distances from the central point of the load plate can be described by the shape of the deflection basin. A modified formula for calculating the assumed deformation of the logarithmic deflection basin is proposed, which is more reasonable than the formula for calculating the assumed deformation of the linear deflection basin; the earth pressure decreases from the center outwards and gradually decreases along the depth direction; the distribution of earth pressure becomes more uniform with increase of the thickness of the hard shell.

Abstract:Field tests were carried out to observe surface settlement induced by twin shield construction in silty fine sand stratum, based on the project of Nantong Metro line 2. The applicability of the twin peck formula for silty fine sand stratum is examined through measured data. The ground loss rate, the width of the preceding tunnel and the rear tunnel were analyzed. The results show that in silty fine sand soil, the secondary perturbation effect of tunnel construction on the rear tunnel induces a significant increase in surface settlement above the axis of the preceding tunnel. The secondary perturbation effect in silty fine sand stratum is more obvious than that in other soft soil layers, but less than that for sand layer. Compared with silty soil layer, the impact of shield stoppage on ground settlement is more significant in silty fine sand stratum. The ratio of ground loss rate η₁/η₂ caused by the twin shield construction ranges from 1 to 5 with a mean value of 2.3, and the ratio of the surface settlement trough width parameter K₁/K₂ between the leading tunnel and the trailing tunnel ranges from 1 to 2 with a mean value of 1.4; The ratios of ground loss rate η₁/η₂ in sand, silty fine sand, and silt soil stratums all exceed 1. Furthermore, none obvious relationship can be found between ratios of ground loss rate η₁/η₂, width parameter K₁/K₂ and the ratio of cover depth to diameter (H/D).

Abstract:For Liujiazhuang railway tunnel of Shanghai-Kunming through the coal strata in construction of large deformation phenomenon, based on theoretical analysis, numerical simulation and field monitoring method, this study investigates the causes of significant deformation in tunnels, focusing on the initial locations of this deformation. It examines the impact of stress states on unit cells aligned with the inclined direction of a coal seam and explores the relationship between tunnel depth and horizontal distance in tilted strata. Additionally, the research analyses the stress and deformation experienced by the element body and the primary support structures in an inclined coal seam. The result showed that the stress state of the coal element above the palm face increases with the horizontal distance between the palm face and the bottom of the inclined coal seam, and the rock mass is subjected to three deformation stages including extrusion, compression shear and shear slip. The large deformation of surrounding rock and the failure of primary support structure both occur in the early stage of shear slip stage, so shotcreting to palm face, grouting reinforcement to coal seam up the palm face and strengthening the stiffness of primary support should be taken to prevent the large deformation of the tunnel in the stage of compression and shear deformation combined with the field monitoring data.

Abstract:The separation and categorization of the basic “global (G), distortional (D), and local (L)” mode classes are necessary for systematical analysis and design of thin-walled members. This paper proposes a new set of basic mode definitions totally based on the orthogonal completeness principle and the force characteristics, which distinguish from the conventional deformation/strain shape-based definitions and are more compatible with complex stress-strain relationships. In contrast to the current general beam theory (GBT) and constrained finite strip method (cFSM), the proposed G, D, and L classes span the entire deformation space of the thin-walled member, and are strictly orthogonal to each other with respect to the stiffness of the member. Buckling mode decomposition and identification according to the proposed definitions are realized based on finite strip models of thin-wall members. Numerical validations confirm the applicability of the proposed method to open/closed polygonal/curved cross-sections, and effects from shear and transverse extension deformations can be reasonably accommodated in the GDL classes. Further, the G, D, and L buckling mechanisms of curved cross-sections are consistent with those of the polygonal ones.

Abstract:In order to study the anchorage property of rebar-metallic bellows slurry anchor connection, 18 groups of connection specimens were designed and fabricated in this study, and the pull-out tests were completed. The influences of anchorage length l_a, grouting material curing age T and spiral confinement on the anchorage property of the connection were analyzed based on the test results. The experimental results show that all the anchored rebars had undergone integral elastic stage and yielding stage, and the ultimate performance of specimens were bond slip failure and rebar fracture. When T=3 d, bond-slip failure occurred in all specimens. When T=7 d and l_a≥13d, rebars fractured. When T=28 d, specimens whose l_a=7d without stirrup and l_a=5d with stirrup began to failure of rebar fracture. With application of spiral confinement and the increase of anchorage length and grout age, the ultimate strength of specimens increased first and then approached to the tensile strength of rebar, the maximum sliding displacement of rebars in the elastic stage decreased significantly, the initial stiffness of specimens increased, and anchorage property improved significantly. In engineering practice, when D/d≥2.6, the anchorage length should be greater than 13d to ensure the anchorage performance of 3 d and 7 d. In order to fully exert its mechanical properties in normal work stage, anchorage length is prohibited to be less than 10d.

Abstract:The wind-induced response of a high-rise chimney can be divided into along-wind response and across-wind response. The along-wind responses are dominated by buffeting vibrations caused by flow turbulence. The across-wind responses are dominated by vortex-induced vibrations (VIVs) caused by Karman vortex shedding. Accurate assessment of these two kinds of wind-induced responses is critical to the wind-resistants design and structural safety of strustures. The two-dimensional wake oscillator model established by Y. Tamura is further derived and successfully applied to the three-dimensional structure in the present study. An iterative calculation method for practical engineering structures is proposed, which provides a new field of vision for VIV predictions of chimney structures. In addition, a complete quadratic combination (CQC) method in the frequency domain is developed for buffeting predictions of high-rise chimneys. The results of frequency domain calculation are compared with those of time domain calculation. The results show that the iterative calculation method can effectively predict the VIV responses of three-dimensional chimneys, and the buffeting responses calculated in the frequency domain are in good agreement with that obtained in time-domain.

Abstract:Rocking timber frame is the main bearing system of Chinese traditional timber structure. The pseudo static test was carried out on the full-scale single-span timber frame model under three-level vertical load. The displacement and deformation characteristics of the timber frame during the test were observed. The hysteretic curve and skeleton curve of the timber frame under low cycle horizontal cyclic loading were obtained to explore its structural characteristics under different vertical loads and low cycle horizontal cyclic loading. In the loading process, the column rocks and the deformation of the column frame layer are concentrated, and the test object can return to the initial position independently in the unloading stage. The test result shows that the hysteresis loops of each stage are long, narrow and overlap. The equivalent stiffness degrades significantly, and the equivalent viscous damping coefficient is low; the residual displacement is between 0.28 mm and 2.53 mm, and the two displacement recovery coefficients are greater than 87.1%. The two type of displacement recovery coefficient does not decrease significantly with the increase of control displacement, so the displacement recovery ability of timber frame is good; the initial stiffness tends to be stable when the control displacement exceeds the yield displacement; the deformation of column frame layer is 2.95 to 86.47 times that of dougong bucket layer. The concentration coefficient of interlayer displacement is between 1.22 and 2.03, which first increases and then decreases with the increase of control displacement.

Abstract:There are usually some defects and deviations in the manufacturing and installation of glulam glued-in rods joints, and there is currently no standard to follow for the design and construction of joints. Therefore, this paper focuses on the influence of installation deviation including manufacturing defects on the flexural capacity of such joints, aiming to clarify the allowable range of installation deviation. Based on the theoretical calculation method to check the beam end flexural bearing capacity of the designed joints, firstly, the finite element analysis of the joints with and without installation deviation was carried out, then the finite element analysis of the joints with installation deviation was compared with the experimental results, and the limit value of installation deviation was determined by using the finite element analysis method considering the cracking of rubber layer. The results show that: the beam end flexural bearing capacity of joints with installation deviations has decreased; the failure modes of the specimens in the test are mainly the yield of the implanted steel bars, the damage of the wood around the reinforcement holes and the cracking of the wood columns along the grain direction. If the installation deviation and adhesive cracking can be reflected in the finite element analysis, the analysis results are in good agreement with the test results. When the installation deviation is controlled within 10~25 mm, the flexural bearing capacity of the joint model is reduced by less than 5% compared to the joint model with the usual reserved gap of 10 mm.

Abstract:The mechanical system of a cable-stayed bridge with a steel arch tower is different from that of a traditional cable-stayed bridge. In order to investigate the effects of ambient temperature variations on the main components of a cable-stayed bridge with a tower in an abnormal shape, an actual cable-stayed bridge with a steel arch tower has been used as the engineering prototype. The online temperature data of the onsite environment and the bridge components were first collected and used to analyze the time-varying effects of the environmental temperature on the cable forces, the tower obliquity and the stress of the main girder. Subsequently, the analysis was focused on the cable forces. The temperature variation simulation was applied to the finite element model of the bridge, and the temperature coupling effects caused by the temperature difference between different bridge components on the cable forces were analyzed. Lastly, the temperatures of the environment, the tower and the main girder were used as the inputs, while the cable forces were defined as the outputs of a long short-term memory neural network. The network was trained using the actual measurement samples of the temperatures and the cable forces. Data compression and feature extraction were realized during the training process. Then, the prediction model for the cable forces was established, and new temperature monitoring data were input into the network model for predicting the cable forces. The analysis results show that the temperature variations of the main girder and the steel arch tower follow a periodic rule and lag behind the ambient temperature. The strain variation tendency of the main girder accords well with the ambient temperature, but the latter has a time lag. The influence of the ambient temperature variation on the obliquity of the arch tower is very small without any periodic rule. A linear negative correlation is found between the cable forces and the ambient temperature. The temperature coupling effect caused by the temperature difference between different bridge components should be considered in the analysis. The long and short-term memory neural network is suitable for the data with timing characteristics. The cable force prediction model based on the neural network has high prediction accuracy, and it can be used for the real-time prediction of this bridge.

Abstract:Due to the uneven transverse settlement of bridge piers caused by the parallel construction of existing and new high-speed railway lines, a CRTS Ⅲ slab track-bridge system static-coupled model was established using the ABAQUS finite element analysis method for a commonly used 32 m standard double-track multi-span simply supported beam bridge in high-speed railways. Considering different settlement types and settlement amplitudes, this paper studies the force between layers of track structure and the deformation law of rail surface caused by the uneven settlement of piers in the transverse direction. On this basis, the static damage classification and maintenance suggestions for the uneven settlement of single and double piers in the transverse direction under this type of bridge are proposed. Based on this analysis, static damage classification and repair recommendations were proposed for single and double-pier uneven transverse settlement of this bridge type. The results have shown that the uneven settlement of the pier in a transverse direction has the greatest influence on the vertical irregularity of the rail surface, followed by the distortion and the horizontal irregularity, and the deformation extremum is easy to appear at the top of the settlement pier. When the unilateral settlement of the pier in the transverse direction of the bridge, the settlement difference between the singer pier of 10 mm, 15 mm and 20 mm, its damage classification is rated as Ⅱ, Ⅲ and Ⅳ. It is necessary to pay attention to the bilateral settlement of the pier across the bridge, and the damage is more serious than the unilateral settlement. When the settlement difference of the transverse direction reaches 20 mm, the transverse tensile stress of the self-compacting concrete layer exceeds the tensile strength limit of C40 concrete, and the track structure has the risk of cracking. It is recommended that the uneven settlement in the transverse direction of the single and double piers should be limited to 10 mm or less for daily maintenance and that adverse settlement of 15 mm or more should be avoided.

Abstract:Permeability is the most important index affecting the durability of concrete. At present, the test methods of concrete permeability, whether water permeability or chloride permeability, have the disadvantages of time-consuming and operation inconvenience. To solve the problem of real-time and in situ monitoring of concrete permeability, this paper studied the evaluation technology of concrete permeability by the resistivity based on the DC-step transient resistance method. The influences of different water-binder ratios, mineral admixtures, water saturation and ambient temperature on the electrical resistivity of concrete were researched. The relationships between the resistivity and the strength, capillary water absorption rate, water permeability and chloride permeability resistance were analyzed. The results show a good association between the transient resistance test and the current permeability methods. The recommended values of transient resistance for evaluation of concrete permeability are proposed, and it is verified that the transient resistance can be used to evaluate the permeability of concrete.

Abstract:Photocatalytic cement-based material is one of the research hotspots of advanced building functional materials, but TiO₂ cement-based composites prepared by the traditional internal mixing method have low effective utilization rate of TiO₂ and poor economic benefits. To solve this problem, cement mortar with quartz sand supported TiO₂ (QST) aggregates were prepared and the effects of the QST aggregates on the drying shrinkage performance of the cement mortar was studied. The interfacial bond strength between the QST aggregates and the cement stone was measured using the pull-out strength method. The effects of the nano TiO₂ on the hydration products and pore structure of the interfacial transition zone (ITZ) between the aggregates and the cement stone were studied via SEM, EDS and MIP methods. Compared with ordinary quarz sand aggregates, the QST aggregates can reduce the drying shrinkage of the cement mortar and improve the interfacial adhesion between the aggregates and the cement stone. The nano TiO₂ that was loaded onto the surface of the aggregates promotes the hydration of the cement paste, reduces the enrichment of Ca(OH)₂ in the ITZ, and refines the pore structure of the ITZ between the cement stone and the aggregates.

Abstract:Occupants, behaviors have great influence on building energy consumption, and family structure is one of the important factors affecting occupants, behaviors. Based on the questionnaire survey and field measure, 12 families with different family structure information such as number, algebra and age in Chongqing were selected, and collect the operating parameters such as air-conditioning opening and closing time in summer. The association rules between family structure parameters and air-conditioning behavior were analyzed by using association rule algorithm, and it was found that the number, algebra and minimum age of members in family structure parameters were significantly correlated with air-conditioning operation time (operation duration and opening time period). Algebra is the most important feature of air-conditioning operation duration in different functional rooms. The air-conditioning operation duration increases with the increase of the algebra. The air-conditioning operation duration of three generations of families in different functional rooms is longer than that of other generations of families. The minimum age is the secondary characteristic of the air-conditioning operation duration of rooms with different functions. In families of the same generation, the air-conditioning operation duration of families with the minimum age of teenagers or preschool children will be higher than that of families with the minimum age of youth or middle age. The main parameters related to the air-conditioning operation time in the family structure characteristics are found out, which provides basic data for predicting the air-conditioning energy consumption and helps the building to save energy and reduce emissions.

Abstract:Compared with traditional phosphorus adsorbents, lanthanum-based materials have stronger affinity towards phosphorus and higher environmental friendliness, which have become the research hotspots of new phosphorus adsorbents. However, in practical applications, lanthanum-based materials have problems such as difficult recycling and low lanthanum utilization. Therefore, in this experiment, the magnetic lanthanum-loaded acidified vermiculite adsorbent (LaFeAVE) with high lanthanum utilization rate, high efficiency in phosphorus removal and magnetic separation was prepared by using acid-activated vermiculite as the carrier, introducing Fe₃O₄ to give it magnetic properties and loading it with lanthanum by solvothermal method and precipitation method respectively. The two kinds of magnetic lanthanum-loaded vermiculite adsorbents (LaFeAVE and LaFeVE) were compared and analyzed by adsorption experiments and various characterization methods to explore the differences in their structures and phosphorus removal performance. In addition, the phosphorus removal mechanisms of LaFeAVE were investigated. The results showed that the acid activation could remove most of the impurities such as Al₂O₃ from vermiculite, which increased its specific surface area and the loading amount of La on vermiculite. The phosphorus removal capacity of LaFeAVE was 15.97 times higher than that of unmodified vermiculite. The adsorption of phosphorus by LaFeAVE was in accordance with the Langmuir isotherm model and the quasi-secondary kinetic equation. Its maximum adsorption capacity at 35 °C was 40.01 mg/g, which was 1.30 times as much as that of LaFeVE, and its time to reach the adsorption equilibrium was shortened by half than that of LaFeVE. It could be used in a wider pH range than LaFeVE and the phosphorus removal rate of LaFeAVE was above 93% in the pH range of 3.00-8.00. LaFeAVE was more regenerative than LaFeVE. Its adsorption capacity of phosphorus decreased by 20% after 5 repeated regenerations. Electrostatic interaction, ligand exchange and intra-sphere complexation reaction were the mechanisms of phosphorus adsorption by LaFeAVE.

Abstract:The occurrence of nano-plastics (NPs) in the aquatic environment has become a global environmental problem. As one of the important primary consumers in freshwater, Daphnia magna is widely used in the biological manipulation and restoration of eutrophic water, while the potential influence of NPs on the feeding behavior of Daphnia magna remains unclear. In the current study, we performed a 21-day experiment and investigated the effect of polystyrene nanoplastics (PSNPs, with size of 1000 nm) exposure on the grazing behavior and physiological response of Daphnia magna toward toxic Microcystis aeruginosa and Scenedesmus oblique. The results showed that in the treatment with toxic Microcystis aeruginosa, the developmental and reproductive toxicity of Daphnia magna were the most obvious. Compared with the control group (feed with Scenedesmus obliquus), the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA) in the Daphnia magna that feed with Microcystis aeruginosa were 3.97 and 4.55 times higher. Meanwhile, the total number of oviposition and body length were decreased by 73% and 13%, respectively. And the filtration rate of Daphnia magna to toxic Microcystis aeruginosa increased with time. Upon exposure to 3.56 mg/L PSNPs, the grazing ability of Daphnia magna was significantly reduced in all treatments, and the feeding rate of Daphnia magna to Scenedesmus oblique was decreased by 32% when PSNPs were added. In the mixed feeding systems containing toxic Microcystis aeruginosa and Scenedesmus obliquus, exposure to PSNPs reduced the feeding rate of toxic Microcystis aeruginosa by 66%, and thereby alleviated the developmental and reproductive toxicity towards Daphnia magna, however, inhibited the reduction of Microcystis aeruginosa biomass.

Abstract:Protein flocculant is a kind of special polymer material produced by animals, plants or microorganisms, which can make the solid suspended particles in the liquid gather and precipitate. Protein flocculant can be directly used as water purifier in some areas due to its good adsorption and flocculation performance. In recent years, with the rapid development of natural water treatment agents, protein flocculants as efficient, and environmentally friendly flocculants are widely favored by researchers. In this paper, the extraction and purification methods, molecular structure and effective functional groups of protein flocculants were reviewed. The research status, performance and mechanism of protein flocculants for removing emerging pollutants in water were summarized. Finally, the prospect of protein flocculants for removing emerging pollutants from water environment was proposed. Protein flocculants have certain advantages as water treatment agents. In the future, in-depth scientific research on protein flocculants can explore their potential value in removing emerging pollutants in water, thus providing a new way to improve the safety of water environment.

Abstract:Sulfur autotrophic denitrification (SAD) has become one of the hotspots in nitrogen removal technology during wastewater treatment because of its characteristic green and low-carbon technology for nitrogen removal from sewage, which has the advantages of low cost, low sludge yield and no need for organic carbon sources. In this paper, the research progress on SAD of carrier compositions and synthesis method of composite sulfur source filler. The structure and applicable conditions of SAD packed bed reactor and fluidized bed reactor were summarized. The research progress of SAD coupled with electrochemical, heterotrophic denitrification and Anammox technology was reviewed. The advantages and disadvantages of SAD coupled technology were summarized. The metabolic function of microorganisms is a key factor in the realization of effective SAD. This review enumerates the types of SAD functional microorganisms with different metabolic characteristics, the denitrification characteristics and growth conditions of Thiobacillus and Sulfurimonas in the SAD process were described. Currently, SAD technology has made significant progress in the fields of filler, reactor and coupling process, but still faces many challenges, further innovations have been made in temperature adaptability of SAD technology, reactor design with high treatment load, and process optimization.

Abstract:In light of the emissions of organized/unorganized waste gases during natural gas extraction, this study conducted an investigation of the occurrence of exhaust pollutants at 16 natural gas extraction stations in the eastern Sichuan region. Subsequently, an evaluation of the health risks posed by the detected waste gas pollutants to both operational personnel and the surrounding population was carried out. The results indicated that, in 2020, the concentrations of H₂S, SO₂ and NO_x detected during the non-operational state of 13 individual well sites ranged from 0.001 to 0.016, 0.007 to 0.023 and 0.012 to 0.047 mg/m³, respectively. These concentrations were comparable to those detected at the JZZ and TD71 wells over a continuous 3-year period from 2017 to 2019, reflecting the consistent emission levels of fixed-source waste gases in the East Sichuan gas field in recent years. Additionally, H₂S, CS₂ and NH₃ were identified as the primary malodorous gases emitted from unorganized sources, but their concentrations remained low and met the secondary standard requirements stipulated in the Emission Standards for Odor Pollutants (GB 14554—93). Furthermore, the health risk assessment results revealed that when the operation of Gas Field Water Tank (GFWT), the Hazard Quotient (HQ) values for H₂S and NO_x at the GFWT and Transfer Water Tank exceeded 0.1, which potentially posing health risks to operational personnel. However, when GFWT was not in operation, the HQ values for H₂S, SO₂ and NO_x at all well sites except TD62, and residential areas were all below 0.1, which indicating minimal health risks for both operational personnel and residents.

Abstract: