Abstract:In order to remove total phosphorus (TP) and organic matter in domestic sewage and achieve partial nitrification, an enhanced biological phosphorus removal granular sludge, which was cultivated with synthetic wastewater at room temperature (17-19 ℃), was used as inoculated sludge in this study. The effect of phosphorus removal and nitrosation on domestic sewage was studied. The experiment showed that the phosphorus removal of the granular sludge could be achieved through 27 d cultivation. The TP concentration of effluent could reach less than 1 mg/L and the TP release in anaerobic stage Δρ_TP/ρ_COD removal in anaerobic stage (Δρ_COD) could reach 0.3. The change of the aeration methods could make R_NA increase from 0 to 90% in a short time. The concentration of NO- 2-N reached 10 mg/L,and the concentration of TP and COD in the effluent were kept below 0.5 and 50 mg/L, respectively. The particle size decreased from 1 200 μm to 1 000 μm and the value of SVI reduced from 32 mL/g to 29 mL/g. The ratio of protein (PN) to polysaccharide (PS) dropped from 2.0 to 1.2. Although the particle size slightly decreased due to domestic sewage, it remained larger than 1 000 μm and the particles possessed better settleability. Thus, the adoption of high and low gradient aeration can achieve phosphorus removal and nitrosation with the removal rate of TP reaching 95%, R_NA reaching over 90%, and the particle performance remaining stable.

Abstract:In order to assess the variations of nitrogen removal performance and nitrogen concentrations at different frequencies of alternating aerobic/anoxic (FAA) and same ratio of aeration time to anoxic time (2 min∶2 min, 4 min∶4 min, 10 min∶10 min, 30 min∶30 min, and 120 min∶120 min), mature partial nitrification sludge from laboratory was inoculated to sequencing batch reactor (SBR) at room temperature (18-20 ℃). Results showed that good partial nitrification was maintained at different FAA. The average nitritation rate and ammonia oxidation rate were 89.7% and 87.1%, respectively. When the aeration time: anoxic time was 2 min∶2 min, total nitrogen removal efficiency (TNE) increased to 88.4% and remained stable. With the increase of the aeration time∶anoxic time (decline of FAA), the TNE tended to decrease, and it reduced to 56.2% when the aeration time∶anoxic time was 120 min∶120 min. Owing that with high FAA (2 min∶2 min), the nitrite generated during the aeration period could be used by the denitrifying bacteria timely in the next anoxic phase, TNE was increased, and FAA was positively correlated with it. Results of beaker experiment showed that the maximum ammonia utilization rate (R_AU) and maximum nitrate production rate (R_NP) were 10.387 and 0.42 mg/(g·h) with the aeration time∶anoxic time of 2 min∶2 min. It indicated that the ammonia oxidation rate was faster with higher FAA, which can reduce the relative amount of nitrite oxidizing bacteria (NOB).

Abstract:To reduce the cost of using sludge anaerobic fermentation products as carbon source and simplify the process, a novel method was proposed to study the feasibility of employing sludge fermentation products directly without separating fermentation broth and sludge or removing nitrogen and phosphorus. Different dosages of sludge alkaline fermentation products (i.e., 0,0, 0,0, and 200 mL, whose SCOD are 0,9, 8,6, and 792 mg) were poured into low C/N ratio municipal waste water to investigate nitrogen removal and phosphorus release. Results show that the nitric oxide (NO-_x-N) decreased first and then increased with the increase of the dosage of fermentation products. When the dosage was 50 mL with SCOD of 198 mg, nitrogen of 12.9 mg, and C/N ratio of 15.3, the concentration of NO-_x-N was the lowest, being only 1.2 mg/L and in the form of NO-₂-N, and the corresponding denitrification efficiency was 94.9%. However, with the increase of the addition of fermentation products, the amount of phosphorus release was not increased but decreased. When the dosage was 20 mL with SCOD of 79 mg, nitrogen of 5.2 mg, phosphorus of 1.6 mg, C/P ratio of 15.3, and C/N ratio of 49.5, the amount of phosphorus release was the highest at the end of the reaction, reaching 23.8 mg/L. Moreover, nitrification and denitrification processes showed that the bacteria activity was inhibited due to the damage of the cell structure of nitrifying bacteria and denitrifying bacteria in fermentation products, which was also proved by cell morphology. It indicated that the introduction of fermentation did not affect the stability of main microbial community structure in sewage nitrogen and phosphorus removal system. Therefore, it is feasible for sludge anaerobic fermentation products to be directly used as carbon source. In this study, the optimal amount for denitrifying nitrogen removal was 50 mL, and that for anaerobic phosphorus release was 20 mL.

Abstract:Aiming at the effect of aerobic starvation environment on the nitrification and phosphorus removal performance of activated sludge and the variations of the microbial community evolution during long-term aerobic starvation periods, an activated sludge with high level removal (>99%) of ammonium and phosphorus was used to study the differences of microbial community structures by Illumina high-throughput sequencing technology during 3,7, 14, and 30 d aerobic starvation periods. Results showed that the performance of nitrification and phosphorus removal decreased with the increase of the aerobic starvation time, and the change of microbial community structure was more obvious with the proceeding of aerobic starvation. During short-term (7 d) aerobic starvation period, the functional bacteria including nitrifiers and phosphorus removing bacteria utilized the released ammonium from cell decay and intracellular storage polymers for cell maintenance to guarantee the recovery of nitrification and phosphorus removal performance. Besides, higher activity resuscitation rate of ammonium oxidizing bacteria (AOB) than nitrite oxidizing bacteria (NOB) contributed to the shift of the nitrification pathway from nitratation to nitritation. Furthermore, the abundances of functional bacteria gradually decreased with the prolonging of aerobic starvation time. The microbial community structures of the activated sludge underwent a dynamic change during the 30 d aerobic starvation period, in which the majority of the original dominant species within the phylum Proteobacteria and Bacteroidetes declined with a remarkable increase of Firmicutes that could acclimatize themselves to the aerobic starvation conditions.

Abstract:In order to develop a new type of disinfection material for water treatment, a new kind of antibacterial material named quaternized chitosan/ silver nanoparticles (QCS/nAg) was prepared by using quaternized chitosan as a modifier of silver nanoparticles, which has synergetic effect and positively charged surface. To study the antibacterial performance of QCS/nAg, neutrally charged and negatively charged nanoparticles were used as comparison to inactivate bacteria, especially Escherichia coli, in water. The function of QCS and nAg in composite materials was evaluated. Furthermore, the antibacterial influencing factors such as material dosage, pH value, and chloride ions were studied. The antibacterial mechanism of QCS/nAg was concluded through studying the dissolution of QCS/nAg and the reaction between QCS/nAg and bacteria, including adsorption and damage of cell wall (cytomembrane). Results showed that QCS/nAg with high dispersibility was successfully synthesized and it performed better inactivation effect than other nAg. QCS and nAg showed synergetic effect in QCS/nAg when treated with bacteria. Compared with PVP/nAg, QCS/nAg exerted superiority in dosing quantity and resistance to interference of chloride ion. The antibacterial mechanism was summarized as that QCS/nAg strengthened the adsorption process of bacteria and the damage to the cell wall (cytomembrane).

Abstract:For conventional wastewater treatment process, the pharmaceutical and personal care products (PPCPs) represented by ibuprofen in municipal wastewater have problems such as weak degradation efficiency, complex structure, and high activation energy. Therefore, based on the internal operational characteristics of biological aerated filter (BAF) and three dimensional electrocatalysis (TDE), a TDE-BAF was constructed to treat ibuprofen in municipal wastewater. Test results revealed that the ibuprofen removal efficiency of TDE-BAF was higher than that of BAF. With water temperature of (21.14±0.05) ℃, COD of (86.82±3.40) mg/L, TOC of (27.56±1.08) mg/L, ibuprofen of (93.2±5.16) μg/L, and ammonia nitrogen of (18.75±2.39) mg/L, the effluent concentrations of ibuprofen were 2.28-9.32 and 57.70-77.12 μg/L, and the average removal rates were 93.48% and 31.89%, which was 61.59% higher than BAF treatment. The removal of ibuprofen by TDE-BAE was mainly in the TDE area (T5-T6), and the removal rate reached 51.78%, accounting for 55.40% of the total removal rate. The mechanism of TDE-BAF degradation of ibuprofen is mainly through the synergistic effect of the TDE and the BAF.

Abstract:Since the pollution of algae blooms has seriously affected drinking water safety for a long time, it is urgent to develop effective techniques to control and reduce algal reproduction. By using Pt/Ti anode and ACF/Ni cathode, effects of the parameters such as cathode materials (ACF/Ni and stainless steel) as well as the concentration and valence state of iron added on the electrochemical removal of algae were investigated to explore the removal efficiency and mechanism of algae in the Pt/Ti-ACF/Ni-Fe²⁺ electrochemical system. Results showed that under the conditions of Fe²⁺ concentration of 0.05 mmol/L, current density of 50 mA/cm², inter-electrode gap of 1.0 cm, initial pH of 6.0, and initial algal cell density of 1.2×10⁹-1.4×10⁹ cells/L, 93% of the algae cells were removed in 15 min. Based on the analyses of ferric ion concentration, H₂O₂ concentration, and pH in the experiments, indirect detection of ·OH, FTIR analysis of ACF, SEM images of algae, and ACF/Ni and BET analyses of ACF, mechanism of algae removal was revealed in the Pt/Ti-ACF/Ni-Fe²⁺ system. H₂O₂ was generated efficiently through electrochemical reduction on the surface of the ACF/Ni cathode, the iron in solid phase generated during the reaction was precipitated on the surface of ACF/Ni cathode with the electrochemical reduction of Fe(Ⅲ) to Fe(Ⅱ), and meanwhile ·OH would be generated in the Pt/Ti-ACF/Ni-Fe²⁺ algae removal system. Heterogeneous and homogenous electro-Fenton processes were the main mechanism in the Pt/Ti-ACF/Ni-Fe²⁺ algae removal system.

Abstract:Aiming at investigating the degradation of low concentration tetrabromobisphenol A (TBBPA) in water and toxicity controlling by ozone oxidizing technology, the degradation of TBBPA (concentration: 0.15 mg/L) was carried out by ozone reactor under different values of pH and different dosages of ozone. The variation and controlling of the acute, chronic toxicity, and genotoxicity of the samples during the reaction were investigated, the internal reasons of toxicity were analyzed, and the possible degradation mechanism was proposed. Results show that TBBPA could be completely degraded when pH is 7.0 and ozone dosage is 0.12 mg/L. At the beginning of the reaction, the acute and chronic toxicity increased rapidly, and it was mainly because of the production of more toxic organic intermediates. As the reaction proceeded, the toxic intermediates were further degraded, and both of the acute and chronic toxicities were effectively controlled and the toxicity was controlled more quickly and significantly with the increase of ozone dosage. When the dosage of ozone was 0.12 mg/L, the acute toxicity could be completely controlled within 20 min of reaction, and the chronic toxicity could be controlled to be 0.76 TU within 60 min. After the reaction, the acute and chronic toxicities of the water samples could meet the emission standard. During the reaction, the mutagenic ratios of the samples were all smaller than 2.0, which had no genotoxicity at the genetic level. The analysis of mechanism showed that the degradation of TBBPA by ozonation mainly included the reaction process of debromination, the beta scission, addition, dehydroxylation, methylation, and so on.

Abstract:To effectively remove the endocrine disturbing chemicals in water, nano Fe₃O₄ supported on the sepiolite was prepared by the method of co-precipitation to catalyze persulfate for bisphenol A (BPA) removal. The catalyst was characterized by XRD, XPS, SEM, TEM, and N₂ sorption experiments. The adsorption capacity toward BPA was studied with different solution pH values and temperatures, and effects of catalyst and persulfate doses on BPA removal efficiency were investigated. Results show that the catalyst with high specific surface area could effectively adsorb BPA, and the equilibrium absorption amount decreased with the increase of temperature, which could reach 11.6 mg/g at room temperature. The BPA (30 mg/L) could be degraded completely within 20 minutes with the catalyst dose of 2 g/L, PDS dose of 4 000 mg/L, and solution pH of 5. The catalyst could be recycled by external magnetic field, and the removal efficiency within 60 minutes decreased only 2.7% after 5 times of recycle. The BPA degradation was accomplished by a coupled process of adsorption and oxidation, and the adsorbed BPA molecular could be oxidized in-situ on the catalyst surface, where the radicals were produced. In this study, the magnetic-modified sepiolite was applied as persulfate activator in the advanced oxidation process for the first time. The coupled process of adsorption and oxidation was considered beneficial to increase the radical efficiency, which could provide a new avenue for trace-level contaminants removal from the point of catalytic oxidation system design.

Abstract:To investigate the impact of light intensity on the growth and photosynthesis activity of Pseudanabaena sp., which is a common species in freshwater cyanobacteria blooms, five light intensity gradients were designed according to the natural light intensity range. Experiments were conducted by pure culture and lasted for 16 days, during which biomass, chlorophyll fluorescence parameters, and the pigment composition of Pseudanabaena sp. were tracked. Results indicated that the optimum light intensity for Pseudanabaena sp. growth was 1 500 lx during 500-2 500 lx. The sequence of the special growth rate of Pseudanabaena sp. from high to low was 1 500 lx, 1 000 lx, 2 000 lx, 2 500 lx, and 500 lx. The photosynthesis activity of Pseudanabaena sp. was significantly correlated with light intensity. After a period of culturing, the photosynthetic rate and the light use efficiency of Pseudanabaena sp. had obvious negative correlation with light intensity, and on the 11th day the correlation coefficients were -0.939 (P<0.05) and -0.978 (P<0.01), respectively. Half light saturation had significant correlation with light intensity, and the coefficient was 0.976 (P>0.01) on the 11th day. Pseudanabaena sp. belongs to low light intensity tolerant cyanobacteria and has self-regulation mechanism that can deal with insufficient or excessive light. It requires relatively low light intensity compared with other algae species and is easy to dominate in water with low or fluctuant light intensity. Outbreaks of Pseudanabaena sp. are relatively unrestricted by water depth and light intensity, so it is not suitable to use vertical disturbance and shading technology for the control of Pseudanabaena sp. Results of this study can contribute to the prediction and control of Pseudanabaena sp. in surface waters.

Abstract:To improve the scientific management capacity of water resources in Harbin priority control section in Songhua River Basin, SWAT model was used to simulate the spatial and temporal characteristics of the water resources. Results show that the spatial and temporal distribution of the water resources in the study area was uneven. The runoff during the flood season was the largest, accounting for 56% of the annual runoff, while that of the dry season was only 16.1% of the annual runoff. The inter-annual runoff ranged from 725 to 2 872 m³/s and the average runoff was 1 320 m³/s. The monthly precipitation in the study area showed a significant upward trend in June and August. The spatial distribution of water resources in sub-basins was different in the years of abundance, normality, and dryness that sub-basins 20 and 23 had greater contributions to the water resources. The contribution rates of runoff in the sub-basin 20 were the highest in the years of abundance, normality, and dryness, which were 10.46%, 8.2% and 11.31%, respectively. The Harbin priority control section was further divided into eight ecological function zones based on the characteristics of water resource sensitivity of sub-basins. Water resources management and utilization plan were proposed combined with objectives of the function zones. The results of this study provide technical guidance for the management and utilization of regional water resources.

Abstract:The rational zoning of aquatic ecological function fully reflects the water environment management idea of “grading, classification, zoning, and staging,” which is an important basis for the management of aquatic environment and water ecosystem. In this paper, the characteristics of natural environment, water ecological factors, and socio-economic activities of the Songhua River basin are analyzed by data fusion technology on ArcGIS software. Based on the three levels of aquatic ecological function in Songhua River Basin, the ecological function importance level of five kinds of aquatic ecological function was evaluated, including habitat maintenance, water conservation, biodiversity maintenance, agricultural production maintenance, and urban support. According to the evaluation results, the Songhua River Basin was divided into 65 water ecological functions of level 4 zoning. Compared with previous methods, this study utilized the data fusion technology, which considered the natural ecology and the impact of social economic factors on the function importance level. The process of the evaluation is more intuitive, and the results are more reasonable and effective. Based on the analysis of the zoning results, this paper provides some reasonable suggestions for the management of the aquatic environment of Songhua River Basin. The results can help identify the characteristics and functional status of the water ecosystem, lay a foundation for the river health evaluation, and provide an important basis for the scientific management of the aquatic ecosystem in the Songhua River Basin.

Abstract:In order to effectively improve the short-term water demand forecasting model of water distribution networks in terms of prediction accuracy and stability, a novel combined prediction modeling method which can predict water demand and residuals simultaneously is proposed in this paper. First, the Bayesian least squares support vector machine method (Bayesian-LSSVM) was used to establish the time series prediction model of user’s water demand (BL model) to obtain the initial water demand prediction values. Then, to predict the residual sequence of the initial water demand prediction values produced by the BL model, a chaotic time series prediction model (RM model) was constructed based on the Bayesian-LSSVM method. At the same time, the predicted residuals produced by the RM model were compensated to the water demand predictions by the BL model to correct the initial water demand prediction values. Results of the case study show that the RM model could accurately capture the change trend of the residual value of the BL model initial prediction values and the residual sequence of the BL model initial water demand prediction values. The combined forecast model consisting of the BL model and the RM model (BL+RM model) was superior to single BL model in the accuracy and stability of short-term water demand forecasting. BL+RM model was applicable for short-term water demand forecasting with different water demand characteristics such as small average water demand and large water volatility, and hence could effectively meet the needs of actual engineering.

Abstract:To ensure the security of urban drinking water, a study was conducted by taking the water source of Mopanshan Reservoir as the research sample, which has low temperature, low turbidity, high chroma, and is rich in natural organic matter. In the study, different disinfectant methods such as liquid chlorine, sodium hypochlorite, and chloramine disinfection were carried out in conventional water treatment process. The study indicated that the disinfection of liquid chlorine and sodium hypochlorite resulted in the formation of trichloroacetaldehyde. However, for the chloramine disinfection method, when the weight ratio of sodium hypochlorite and ammonium sulfate reached 4∶1 (2 mg/L∶0.46 mg/L), the by-product of disinfection especially trichloroacetaldehyde decreased significantly. Moreover, the disinfection lasted longer, which provided more stable disinfection effect for pipe-network water. Chloramine disinfection method was superior to conventional liquid chlorine and sodium hypochlorite disinfection in the decrease of by-products produced in drinking water disinfection, and its indexes met the requirements of Drinking Water Health Standards (GB5749-2006), which solved the problem of overmuch trichloroacetaldehyde in pipe-network water.

Abstract:To improve the dynamic response of tapered piles and its application theory, the Winkler model was adopted to simulate surrounding soil, and the frequency domain and time domain responses of longitudinal vibration velocity of the pile top were obtained with the pile vibration equation simplified by changing variable, in which the pile was assumed to be elastic with gradually varied diameter and its body was divided into non-equal-section parts. The variable control method was adopted to investigate the influence factors. Results showed that the calculation results of the proposed model were similar with those of the traditional simplified model when soil shear wave velocity was low. However, the difference between the proposed model and the traditional simplified model became more significant as the shear wave velocity increased. For three geometric feature parameters, calculations showed that pile length L mainly affected the signal intensity of pile bottom. The longer the pile length was, the lower the reflected signal peak was. The radius R_m and cone angle α mainly affected the position of curve in C area, and slightly affected the reflection signal of pile bottom. With the increase of the compressional velocity (elastic modulus), the reflection signal of pile bottom and the amplitude of frequency response curve became more significant.

Abstract:The quartz-mica schist is a typical schistosity rock and its structural features are distinct from stratified or layered rocks. Its specific property leads to different deformation and failure mechanism between the quartz-mica schist and stratified or layered rock. Because the quartz-mica schist is easy to disintegrate in water and the angle of schistosity plane can change significantly, it is difficult to systematically carry out the mechanical test of the rock samples with different angles due to sampling difficulties and rock variability. As a research method commonly used in the field or rock mechanics, physical simulation method conducted on similar materials is frequently used to qualitatively explore the mechanical properties and behavior of rocks. The structure and tectonic characteristics of the quartz-mica schist were revealed by electron microscopy and polarized light microscopy, and the deformation and failure mechanism was analyzed from macroscopic and microscopic perspectives according to the experimental result. The device and method for making materials similar to schistosity rock were developed, and the corresponding physical simulation material was obtained. The mechanical behavior, failure characteristics, and mechanical parameters of the similar material were studied by means of uniaxial and triaxial tests. Based on the apparent analysis of material structure and the results of mechanical tests, the reliability of the device, the feasibility of the proposed method, and the similarity of the material itself were verified.

Abstract:The stability and reliability of unstable rock in the sliding failure mode are controlled by the discontinuous structure. The variability of the connection rate of the structural plane, the section intensity parameters, and the force on unstable rock exerts high degree of uncertainty on the reliability of unstable rock. This paper presents a method for the reliability analysis of unstable rock controlled by discontinuous structure. Based on Monte Carlo method, the reliability calculation method of unstable rock mass with uncertain structure and uncertain force parameter was established. The sensitivity of each factor corresponding to the instability probability was analyzed and the dominant factor was determined by orthogonal test. Through the response surface design method, the influence of the dominant factor parameter variability on reliability was analyzed. The study on the Nanmenwan unstable rock belt shows that the connection rate and cohesion of unbroken segment are the main factors that influence the reliability of the rock mass, and the influence of variation of the two parameters on the reliability of unstable rock mass is controlled by their mean size. When the selected mean value causes the unstable rock mass to become unstable, the probability of instability will increase with the decrease of the coefficient of variation and the low variability will lead to an overly conservative assessment of reliability. The coefficient of variation is positively correlated with the probability of instability as the mean tends to be the stable segment of the unstable rock mass, and low variability parameters may result in a non-conservative estimate of the reliability of hazardous rocks. The study provides references for the reliability evaluation of this kind of unstable rock.

Abstract:To make full use of the gelation activity of hemihydrate phosphogypsum and use hemihydrate phosphogypsum as mine filling cementing material, the physicochemical properties and micromorphology of hemihydrate phosphogypsum were analyzed by XRD, XRF, and SEM. Through the orthogonal experiment, the best ratio of hemihydrate phosphogypsum filling materials was obtained: the content of quicklime is 1.5%, the content of tailings is 0%, and the content of crystal water is 5%. The single-factor experiment shows that the strength of hemihydrate phosphogypsum has a positive correlation with the dosage of lime and the stirring time, and is negatively related to the content of crystal water, the content of water soluble phosphorus, and the amount of tailings mixed with hemihydrate phosphogypsum. To make the 3 d strength of the hemihydrate phosphogypsum filling material reach 3 MPa, the amount of lime in the filling material should no less than 1.5% and the stirring time no less than 10 minutes. At the same time, the content of water soluble phosphorus in the raw material of hemihydrate phosphogypsum should be less than 4%, the content of crystalline water should be less than 10.3%, and the content of the tailings no more than 60%. Microanalysis shows that the strength of hemihydrate phosphogypsum filling body is influenced by the crystal morphology of hydrated phosphogypsum, the strength of the contact, and the volume rate of hydration products.

Abstract:In underground engineering, especially in deep excavation engineering, in-situ stress is one of the important parameters of the guiding excavation, thus the measurement of in-situ stress is crucial. The CSIRO in-situ stress measurement method is recommended by the International Society for Rock Mechanics. The deep granite of the Sanshandao Gold Deposit was processed into standard cylindrical specimens. The Hoek-Brown strength criterion curve was obtained by uniaxial and triaxial compression tests. A single rock sample multi-confining pressure step loading test considering multiple confining pressures was designed. Physical parameters such as elastic modulus and Poisson’s ratio were obtained by calculation of experiment data. Deformation parameters including bulk modulus K and shear modulus G were introduced, and the mean stress increased following a non-linear manner. The constitutive relation between the bulk modulus and shear modulus vs. mean stress was fitted by the hyperbolic function K/G=K₀/G₀+Pb+a×P, where K₀/G₀ is the initial modulus of deformation, K₀/G₀+1/a is approach value of mean stress at limit, 1/b is initial growth rate of deformation modulus, all of which have clear physical meanings. Based on this formula, the high-pressure biaxial formula in the CSIRO in-situ stress measurement method which considers the non-linear elastic deformation of rock was deduced, and its applicability was verified by rock core removal high pressure biaxial loading test conducted on the deep granite of Sanshandao Gold Deposit.

Abstract:To study the influence of joint dip angle on rock mass damage, the damage evolution model and damage constitutive model of jointed rock mass were built considering the combined action of joint and load based on damage mechanics theory. The model test was verified by the single weak surface theory, and the damage evolution characteristics of the jointed rock mass were investigated. Results showed that the theoretical results of single weak surface theory were in good agreement with the experimental results. The model test could better characterize the mechanical characteristics and damage evolution law of the rock mass with single structural plane under load. The initial jointed damage showed an inverted U-type distribution that it increased first and then decreased with the increase of the joint dip angle, and it reached the maximum value when the dip angle was 60°. The total damage curve showed an S-type distribution that it grew slowly first, then rapidly, and finally slowly approached 1. The joint dip angle only affected the magnitude of the total damage rate instead of its evolution trend. The total damage rate curve showed a normal distribution that it increased first and then decreased with the increase of the strain. The total damage rate was affected by the distribution of the joint plane, which decreased first and then increased when the joint dip angle increased from 0° to 90°.

Abstract:To analyze the formation and evolution mechanism of shear bands and clarify the macroscopic and microscopic relationship of the interface parameters of the soil in the pull test, by employing particle flow code (PFC 2D), geogrid-reinforced glass sand numerical pull-out tests were conducted on the basis of discrete element numerical simulation, whose results were compared with those of laboratory tests. In the numerical test, the nonlinear stress-strain relationship of the geogrid was reconstructed by using the piecewise function. According to the sand particle displacement, the average thickness of shear bands was determined. Factors such as contact force chain, particle displacement, and particle rotation as well as relations between the major principal stress direction and parameters of fabric anisotropy were analyzed. Results show that DEM could better analyze the mechanical behavior between the interface of the glass sand particles and the geogrid under small geogrid displacement, and volume dilatancy of the sample was mainly controlled by the motion of particles in shear zone. The program for Particle Rotation Color Displaying, developed by FISH language, showed that particles in the upper and lower interfaces of geogrid had different rotation modes and displacement and rotation of the particles formed shear zone with serrated distribution, which revealed that particle displacement and rotation were important characteristics of the evolution of shear band. The distribution of contact force and the evolution of fabric anisotropic determined the macroscopic mechanical properties and the basic shape of the shear band. During the shearing, the deflection of the direction of the major principal stress was similar to the orientation of contact force anisotropy in the shear band.

Abstract:To solve the problem of surface lifting caused by grouting in urban shallow underground projects, grouting lift calculation method and simplified algorithm were established based on the theory of stochastic medium, and effects of compaction grouting and fracture grouting on surface uplift were studied. Through PFC simulation and laboratory model experiments, the suffering area of the surface uplift by ball compaction grouting and horizontal fracture grouting were studied, and the accuracy of the grouting lift calculation method of surface uplift displacement was verified. Effects of grouting depth, soil dry density, and soil water content on surface uplift during grouting were investigated by introducing the grouting uplift coefficient γ. Results show that the simplified method of theoretical prediction of surface uplift displacement was accurate when the depth of grouting was greater than 2 m, and it was not applicable when the depth of grouting was less than 2 m. The surface uplift caused by the two grouting methods was consistent with the results of the numerical simulation and the mathematical model calculation. Single hole grouting changed the displacement field of the overlying inverted cone soil. The maximum surface displacement caused by compaction grouting was large, so was the influence range of fracture grouting on the surface. Factors such as grouting depth, soil dry density, and soil water content all influenced the maximum surface displacement caused by grouting, among which grouting depth was the most important factor.

Abstract:Dry-wet cycle and chloride ion (Cl^-) penetration are the main factors affecting the durability of marine concrete. To study the influences of different environmental conditions and the addition of nano-particles on the Cl^-penetration resistance of marine concrete, nano-SiO₂ and nano-Fe₃O₄ were respectively added into ordinary concrete with different amounts, and the contrast test of Cl^-penetration was carried out by dry-wet cycle and full immersion, then the Cl^- content in concrete at different depths by chemical titration was measured. The test results show that dry-wet cycle accelerates the Cl^-migration to the inner of concrete, which makes that the total Cl^- content, free Cl^- content and bound Cl^- content in concrete and the Cl^- binding capacity of concrete under dry-wet circle condition are all higher than those under full immersion condition at the same age, and the difference in Cl^- content between the two environmental conditions becomes more and more larger with the increasing number of dry-wet cycles. Under the two environmental conditions, the total Cl^- content and free Cl^- content in concrete with nano-particles are all lower than those in ordinary concrete, but the bound Cl^- content and the Cl^- binding capacity are all higher than those in ordinary concrete. The optimum amount of two nano-particles in marine concrete is 2%, and the Cl^-penetration resistance of concrete with nano-SiO₂ is superior to that of concrete with the same amount of nano-Fe₃O₄. The surface effect and filling effect of nano-particles improve the pore structure of concrete, resulting in the Cl^-migration in concrete difficult. Both nano-SiO₂ and nano-Fe₃O4 with different amounts can enhance the chemical binding capacity and physical adsorption capacity of hydrated products to Cl^- in different extent, which can reduce the free Cl^- content in concrete to improve the Cl^- penetration resistance of marine concrete. This study can provide references for the durability design of marine concrete.

Abstract:This paper analyzes the influence of urban outdoor leisure sport space (OLSS) factors on leisurely physical activities (LPA) between genders by a survey in Harbin. A model about the relationship of OLSS factors and LPA was established by the Structural Equation Model (SEM). Using simultaneous analysis of several groups of SEM, the genders as moderator variables were introduced into the model to test the influence of OLSS factors on LPA between genders and the corresponding difference. Result shows that in the male group, facilities, accessibility, amenities, aesthetics, maintenance, and safety had significant impacts on the frequency of LPA. There was no OLSS factor that affected the duration of LPA, and facilities had a significantly greater impact on frequency than accessibility. In the female group, factors that impacted frequency of LPA were identified as facilities, amenities, aesthetics, maintenance, and safety. The two factors which impacted the duration of LPA were facilities and physical environment, and physical environment had a significantly greater effect on duration than facilities. By comparing the two groups, accessibility had significant influence on the frequency of males LPA and physical environment greatly affected the duration of females LPA. Amenities had a greater impact on the physical environment in the female group. The influence and disparities of those relationships in different gender groups were analyzed and interpreted, and the suggestions for designing OLSS considering different gender characteristics were proposed.

Abstract:In order to study the running safety and derailment mechanism of high-speed railway under earthquake, a full-size vehicle-track model shaking table test was carried out by using a 6 m×6 m large-scale shaking table. Based on the shaking table test, a similar multi-freedom and multi-rigid-body vehicle-track numerical model was established, and the test results were compared with the calculation results. The two results were basically consistent, indicating the validity of the numerical calculation model. Then, according to the safety reserve of derailment coefficient and other indicators between the normal running state and the earthquake state of the train, a new idea for determining the earthquake early warning threshold of high-speed railway was proposed. On the basis of the vehicle-track numerical model, time-lapse analysis was carried out by inputting 6 different horizontal seismic waves. The relationship between the derailment coefficient, the wheel load reduction rate, and the peak acceleration of seismic wave was analyzed. Finally, the warning thresholds corresponding to different derailment coefficient limits and different wheel load reduction rate limits were given, and it was suggested that the earthquake warning threshold of China’s high-speed railway should be set to 40 gal.

Abstract:Membrane biofouling is a phenomenon where bacteria adhere to the surface of membrane material and form biofilm, resulting in the block of membrane holes and decrease in membrane flux. The problem of membrane biofouling largely increases the extra energy consumption and operating cost in the operation and maintenance process of membrane bioreactor (MBR), which has become the main bottleneck that limits the efficient and stable operation of MBR. The quorum quenching (QQ) technology based on the quorum sensing (QS) theory is an emerging and effective method for biofilm inhibition, which has achieved much attention in the field of membrane fouling control. The QQ technology can hinder the genetic expression of signal molecules by disturbing the quorum sensing system of bacteria, which effectively restrains the extracellular polymeric substance (EPS) secretion of bacteria and ultimately decreases the biofilm formation on the membrane material. This review introduces the QS and QQ theory, function of the QS theory in the formation and disintegration of biofilm, and three approaches to realize QQ technology. The membrane fouling control methods based on QQ technology are introduced from the perspective of QQ reagents (compounds, enzyme, and bacteria) additions. Furthermore, the immobilization technologies of QQ reagents in QQ membrane fouling control and their potential applications in MBR are summarized according to the latest research progress at home and abroad. Finally, an outlook of future research in QQ membrane fouling control technology is proposed.