Abstract:To explore the effect of undulating angle and normal stress on the shear strength and deformation of the rock with regular saw-tooth joints, direct shear tests were carried out on the limestone samples with different undulating angles under different normal stresses. Subsequently, a shear strength estimation formula was established and verified. The results show that,under the same normal stress, according to the morphological characteristics，the shear stress-displacement curves can be divided into three types：the sliding curve, the sliding-peak curve and the peak curve. The sliding curve and the sliding-peak curve can be divided into nonlinearly slow rising, linear steep rising, and “upward convex” slow rising stage, approximately straight and flat stage. The peak type curve can be divided into nonlinearly slow rising, linear steep rising, “slightly convex” rising, brittle falling and gently descending stage. The failure mode of rock with saw-tooth joints with different undulating angles can be generalized into three failure modes: sliding failure, climbing failure and gnawing failure. The evolution of joint damage under each failure mode can be divided into three stages, i.e., the sliding failure mode can be divided into compaction, friction-over-coming and sliding stage. The climbing failure mode can be divided into compaction, climbing-sliding and plastic flow stage. The gnawing failure modes can be divided into compaction-climbing, climbing-gnawing and gnawing-sliding stage. The shear strength increases with the increase of the normal stress and undulating angle, and the evolution of shear strength still follows M-C criterion.

Abstract:The soft soil of silt underneath the miscellaneous fill can be easily squeezed into the pores between the particles of the miscellaneous fill under overlying loads, resulting in mutual embedding settlement, which is failed to be taken into account in traditional foundation settlement calculations. But miscellaneous fill has the property of uneven grading, and its porosity is closely related to its particle size component. This paper selected four different particle size groups, a binary mixture of heterogeneous soil particles of different particle sizes was studied, used self-made embedded instrument to investigate the evolution pattern of total settlement and mutual embedded settlement under the different particle size ratios and small particle content of miscellaneous fill by tests. The results indicate that: under binary mixed granular composition, when small particles occupy the body, mutual embedded settlement increases with increase of small particle size, when the content of large and small particles is the same, the mutual embedded settlement tends to decrease first and then increase with increase of the particle size of small particles, when the content of small particles is less, the mutual embedded settlement decreases with increase of particle size; and in the process of particle content change in miscellaneous fill, when the particle size of the small particle is small, mutual embedded settlement decreases with increasing particle content, when the particle size is large, the increase of particle content does not have much effect on the intermixing settlement between the miscellaneous fill and the soft soil.

Abstract:Soil suffusion induced by long-term seepage generally lead to deformation or damage of soil structure. The suffusion experiments of silty sand had been accomplished by the independently developed seepage instrument, to study the particle loss process and suffusion evolution characteristics of silty sand with different void ratios induced by seepage of different hydraulic gradients, and the influential mechanism of factors is understood on the sand suffusion, then a model is established to predict the increase of particle loss with seepage duration and hydraulic gradient. Furthermore, the development patterns are revealed of particles size distribution and void ratio during suffusion based on the particle grading test and three phases relationship. The results show that: firstly, fine and sandy particles are both washed away by the long-term seepage and some dominant seepage channels will form subsequently in the samples, and then the internal local collapse and the overall differential settlement will be induced by continuous suffusion, until the water pressure mainly dissipates along the dominant channel to achieve the suffusion stability. Secondly, the initial void ratio or compactness is the main internal factor affecting the degree of the seepage suffusion of the soil, which directly changes the hydraulic gradient threshold, loss rate, cumulative total mass of particle movement and settlement deformation of sandy samples. The increase of the hydraulic gradient will also accelerate the particles loss, channel formation and suffusion stability. Thirdly, the prediction model fits the experiment result well, which can reflect evolution characteristics above and the influence on particles loss process of initial void ratio as well as the hydraulic gradient. Finally, the void ratio of samples will increase and the uniformity of particle size will decrease during sand suffusion.

Abstract:In order to study the mechanical strength deterioration characteristics of the stone site under the effect of water saturation and to determinethe seepage and migration path of groundwater, lab micro-tests, macro-tests and field seepage tests are comprehensively conducted on multiple scales. The microscopic tests include polarized light microscope (PM), X-Ray diffraction (XRD) and porosity test, the macroscopic tests include water absorption test and uniaxial compressive strength softening test, and the on-site testing mainly adopts high-density resistance method to image and analyze the water-bearing rock layer. The petrographic identification results show that 1) the overall lithology is sandy mudstone, and the mineral composition is mainly of quartz and feldspar. Illite is the main clay mineral. This kind of rock has poor resistance to wetting and drying cycle. The saturation coefficient of sandy mudstone is between 0.84~1.00, and the softening coefficient is between 0.55~0.65, indicating a soft rock, and its high softening is the main reason for the deformation of formation structure. 2) Under the action of surface water, the mudstone is exposed and tectonic fissures are formed, some rock surfaces are sabjected to salt precipitation problem, and the slope is unstable and deformed under the coupling action of seepage and stress. The field detection of high-density resistivity method shows that the groundwater leakage leads to a low resistance zonebelow, and the resistivity is below 20 Ω·m, which is mainly caused by seepage of the canal.

Abstract:The reinforced concrete piles (RC) in integral abutment bridges (IAB) are challenging to meet the longitudinal deformation of bridges with significant lateral stiffness. This paper proposes a new form of pile comprised of UHPC and RC piles in series to meet the longitudinal deformation demand of IAB. Tests were conducted for two UHPC/RC segmental piles (with or without prestressing). The failure characteristics, hysteretic behavior curves, skeleton curves, equivalent viscous damping ratio, and rigidity degeneration were developed using horizontal displacement loads. The failure position of the non-prestressed segmental piles is at the buried depth of three times the diameter of the pile, the displacement of the pile top when the pile cracks is 8-10 mm; the failure position of the prestressed segmental piles is at the buried depth of four times the diameter of the pile, The displacement of the pile top when the pile cracks is 10-15 mm. The results show that prestressing can effectively improve the resistance cracking capacity of step piles and seismic properties, while meeting the deformation requirements of IAB. The finite element model (OpenSees) was used for modeling and analysis. The analysis results show that the horizontal bearing capacity and deformation capacity of stepped pile can be improved by the increase of prestress degree, the ratio of length and stiffness of pile.

Abstract:The engineering properties of coral sand are special, so it is important to study the bearing characteristics of coral sand foundation for island construction. The influences of relative compactness and water content state on the bearing deformation characteristics, particle breakage, layered settlement and the pattern of earth pressure transfer of coral sand foundation are studied through the plate loading model test of coral sand foundation under different working conditions, such as different relative compactness (50%, 65%, 72%, 80% and 85%), different water content states (dry or saturated) and water level variations. The results show that the bearing capacity of coral sand foundation increases and the settlement decreases with the increase of relative density in dry condition. The coral sand particles are broken more significantly while the relative compactness is greater than 80%. The earth pressure directly below the bearing plate decreases with increase of depth. The bearing capacity of coral sand foundation in saturated state is about 44% of that in dry state, the settlement in the failure is about 2 times of that in dry state, and the influence of two times of water level variation on the bearing capacity and settlement of foundation is small. At different locations from the center of the bearing plate, the developments of the layered settlement of coral sand foundations in saturated, water level variation and dry state are different. The pattern of earth pressure transfer is similar in the three states.

Abstract:Geosynthetic can be used as an encasement for conventional stone column, forming geosynthetic encased stone column (GESC). This method can reduce the lateral displacements of stone column and improve the bearing capacity in soft clay through the radial restraint of geosynthetic encasement. This paper presents a numerical study to investigate the dynamic response of GESC in soft clay foundation. Both the stone column and the soft clay were characterized using nonlinear elasto-plastic models that consider the hysteretic behavior. Geosynthetic encasement was characterized using linearly elastic geogrid elements. The 3D dynamic numerical model was validated using shaking table test results published. A parametric study was conducted to investigate the influences of geosynthetic encasement stiffness, soft clay shear modulus, and embankment loading on the dynamic response of GESC in soft clay foundation. The results show that with the increase of geosynthetic encasement stiffness and soft soil shear modulus, the decrease of embankment load, the settlement of stone column and the strains of geosynthetic encasement and soils could be significantly reduced. Geosynthetic encasement could effectively improve the seismic performance of stone column in soft clay foundation.

Abstract:A periodic foundation (PF) plate with rotational oscillators was used for the bending wave isolation of high-rise buildings. Previous studies concerning the PF focused on the in-plane waves. However, seismic waves easily excite bending waves for the periodic foundation plate structure. This study broke through the limitation of plane wave research by studying the bending wave dispersion curves. The finite element method was employed to calculate the bending wave Attenuation Zones (AZs) of the PF plate by the SHELL element which can consider the influence of the plate thickness of the plate. The influences of the material and geometrical parameters on the bending wave AZs were comprehensively investigated. The effectiveness of the PF was demonstrated via a three-dimensional finite element model under incident harmonic bending-waves and seismic waves. The results show that the bending wave AZs are sensitive to the width and elastic modulus of the linkers. The bending wave AZs of the PFs were lower than 10 Hz, and the seismic isolation efficiency was greater than 60% compared to the concrete foundation, which is sufficient for it to serve as a seismic isolation foundation for high-rise buildings.

Abstract:The traditional anti-sliding sheet pile wall is prone to irreparable damage and deformation under strong earthquake. Engineered Cementitious Composite (ECC) has high tensile strength and tensile strain hardening characteristics, and is superior to conventional reinforced concrete in terms of restricting crack development, bending capacity and energy dissipation capacity. But the seismic performance of ECC anti-sliding sheet pile wall supporting structure is not clear yet. Therefore, shaking table tests are carried out on ECC pile-sheet wall (ECC pile-sheet) and RC pile-sheet wall (RC pile-sheet) to compare their dynamic response and failure characteristics. The results show that the seismic performance of ECC pile-sheet is better than that of RC pile-sheet. Under the same ground motion amplitude input, the dynamic response of the slope under ECC pile-sheet is less significant than that under RC pile-sheet, and the ECC pile-sheet with the same compressive strength can ensure the stability of the slope under the action of higher ground motion. ECC pile-sheet and RC pile-sheet show obvious elastic and elastic-plastic stages under dynamic action, and the dynamic responses of the two pile-sheet are consistent when the ground motion is small. When the amplitude of ground motion is large, the acceleration amplification coefficient of slope under ECC pile-sheet is 0.77-0.9 times that under RC pile-sheet. The soil pressure distribution of ECC pile-sheet and RC pile-sheet is "bimodal", and the peak of soil pressure behind RC pile is about 5 times that of ECC pile. The pile top residual displacement and magnitude of the two pile-sheet are distributed in exponential form, and the residual displacement of RC pile sheet is twice that of ECC pile-sheet. In the failure stage, ECC pile-sheet only has several fine cracks on the fixed part, RC pile-sheet is of bending failure characteristics, steel bar and concrete slip obviously, and the displacement is uncontrollable.

Abstract:This paper aims to explore the influence of bedding angle on layered soft rock tunnel under different deformation grades. Based on the large deformation soft rock tunnels along the Jiumian Expressway, the parameters of ubiquitous joint model were determined through rock mechanical test. Based on the numerical simulation, the influence of bedding angle on the stress and deformation of surrounding rock and supporting system of large deformation tunnel in layered soft rock was studied under different soft rock large deformation levels (slight, medium and strong). The results of numerical simulation were verified by field statistical law of bedding angle and large deformation. The results show that: 1) The deformation and stress of surrounding rock and the supporting structure with small angle (0°, 15°) and large angle (90°) of bedding are large, with the increase of large deformation grade, the effect of surrounding rock and support changes caused by bedding angle is more obvious. 2) The deformation of surrounding rock gradually shifts from the arch bottom to the right arch waist with the increase of bedding angle. The surrounding rock deformation mainly occurs at the position where the tunnel contour is tangent to the bedding plane, and the arch bottom and left arch foot are sensitive to bedding angle. 3) The deflection of the initial support stress and the plastic zone of the joint are roughly consistent with the normal direction of the weak plane of bedding. With the increase of bedding angle, the shear plastic zone of joints shifts from vault and arch bottom to left arch foot and right arch shoulder, and finally shifts to the upper and lower position of left and right arch waist. The initial support tension stress is more sensitive to the bedding angle than the compressive stress, vertical joints increase the risk of tensile and shear failure plastic zone transfixion, but the radius of plastic zone in shear failure may decrease. 4) The statistical law of the site is that the large deformation grade of small angle and large angle is higher,strata failure occurred in the waist and shoulder of the arch when the bedding angle is below 60°, the failure of rock strata tends to develop to the spandrel with the increase of bedding angle. Rock failure mainly occurs in the arch waist at large bedding angles.

Abstract:For serviceability limit state of geotechnical structures at a specific site, the scatter among the load-displacement curves of bored piles, floating anchors or CFG piles is considered, and the set of regression parameters obtained by fitting these test curves is treated as a random variable. On the basis of theoretical framework of the geometric reliability method, a Gaussian Copula function is used to facilitate the transformation of random variables from the standard normal space to the original physical space, and then an inverse reliability algorithm based on probability density contours (PDCs) is constructed. In this algorithm, if one parameter of a normal probability density distribution is unknown, such as the mean or coefficient of variance, the PDC of the random variables can be derived when a target reliability index is specified. If the PDC is bounded by the limit state equation, the unknown mean value or coefficient of variance for the random variable under a given target reliability index is solved, and the corresponding safety factor is derived. While a non-normal marginal distribution is followed by random variables, the geometric configuration of the PDC can be still approximated by a set of discrete points, and the inverse reliability analysis is also applicable. The proposed algorithm is mainly used to solve problems with statistical parameters of random variables missing or incomplete. When the target reliability index is specified, the safety factor can be calibrated according to the importance hierarchy of the structure.

Abstract:For strutted or anchored retaining structures, the anti-overturning stability around the fulcrum needs to be checked for the berm-retained excavations. However, a reasonable calculation method has not yet been found. Based on the upper limit theorem of limit analysis, three possible failure modes of the berm-retained excavations were proposed, the slice method with inclined interfaces was used to separate the passive soil area, and a compatible velocity field was constructed. The expressions for calculating the anti-overturning moment of foundation pit under three failure modes were derived respectively. Through the calculation example, the effects of friction coefficient between retaining structure and soil, soil cohesive force and the berm-retained geometric parameters on the rupture angle and anti-overturning moment were analyzed by using genetic algorithm. The results show that when the wall is smooth and the soil cohesion is zero, the anti-overturning moment calculated by Rankine's passive earth pressure theory is an upper bound solution. When cohesive force exists, the theoretical value of Rankine's passive earth pressure theory is conservative, when friction coefficient exists, the anti-overturning moment calculated by coulomb earth pressure theory is too large. In addition, the berm-retained height has a more significant influence on the anti-overturning moment than the berm-retained width and slope.

Abstract:In order to deeply understand the progress of research on structural damage of ballastless track under temperature and high-frequency train load, the primary structural forms of ballastless track and its advantages and disadvantages were summarized, the current status of research on the temperature field and temperature effect of ballastless track was reviewed, and the process of occurrence, development and change the law of interlayer interface damage under different forms of temperature load was focused on. The static properties of roadbeds and ballastless tracks on bridges under static forces and the mechanism of fatigue damage evolution under fatigue loading were presented. The current state of research on the mechanical response of ballastless track structures under coupled temperature-train loads and the major difficulties were discussed. Summarized the current research limitations and further looked forward to future development trends. Research results show that the regional difference of solar radiation has little research on the temperature action mode and value of ballastless track, and the design specification has no specific description. In the future, the temperature action of ballastless track should be accurately calculated in combination with historical meteorological data, and the isotherm maps of the temperature effect of ballastless tracks in different regions should be drawn to improve the accuracy of structural temperature action value and temperature calculation theory. The damage research of temperature and train dynamic load on ballastless track structure is mostly concentrated on the overall structure, and the damage evolution of detailed structure is not studied in depth. To quantify the mapping relationship between each parameter of ballastless track and structure by combining track details, components and overall structure, indoor accelerated test and field test, numerical analysis and experimental research in response to the actual standard project. Due to the limitation of test conditions, the existing temperature load and mechanical test are all carried out in sections, and the performance study under the coupling effect of temperature and train load is only carried out on the ballastless track from the perspective of numerical simulation. Under the background of single-load research, further breakthroughs are made in the multi-scale model test method and the multi-field coupling refined numerical analysis method under the coupled effect of temperature-train load, revealing the coupled dynamic behavior of temperature-train load and the instability mechanism of the track structure. The complex temperature and vehicle load coupling effects based on cyclic temperature, continuous high and low temperature, etc. have rarely been published. Probing the damage evolution mechanism of ballastless track under complex temperature-train load coupling. Optimize the design of ballastless track system, and improve service evaluation criteria for track structure performance under coupling action, to provide a reference for the actual project.

Abstract:One of the important inelastic characteristics of reinforced concrete columns during the strain-softening stage is the buckling and the fracture of longitudinal reinforcement after tension-compression cyclic loading. However, there are few low cycle fatigue damage models considering the influence of buckling, and a few fatigue damage models considering buckling cannot be directly used for fatigue damage calculation and fracture analysis of steel bar with different strength. In this paper, the specimens of HRB400 reinforcement and HRB500 reinforcement with slenderness ratios of 6.25, 9.375, 12.0 and 15.0 were subjected to tension compression equal cyclic loading and tension compression unequal cyclic loading considering buckling respectively. The average stress-strain (σˉs-εˉs) curves and mid-span transverse displacements of buckled specimens were measured. Combined with the corresponding test results of HRB600 reinforcement completed by the author, a systematic test data was constituted. Based on the test results, the effects of yield strength and slenderness ratio on the ultimate deformation capacity of buckled reinforcement were analyzed, the applicability of the traditional low cycle fatigue damage model (C-M model) and the modified C-M model based on the total average strain amplitude εˉsa to the buckled reinforcement was investigated, and the errors were analyzed. A modified C-M fatigue damage model based on cyclic total average strain amplitude εˉ_sa-cyc with good applicability was proposed. The results show that specimens with different strength have different low cycle fatigue performance due to the different mechanical properties of steel bar, such as εsu，εsult and fu etc. The ultimate deformation capacity of buckled steel bar under cyclic loading is related to low cycle fatigue damage, the fracture of steel bars cannot be correctly determined by the ultimate tensile strain εsu under monotonic tension. The modified C-M model based on the total average strain amplitude εˉsa cannot reasonably consider the influence of different loading methods on the low cycle fatigue life of buckled reinforcement, and there are systematic errors. The modified C-M model based on εˉ_sa-cyc can reasonably consider the influence of different loading methods, and can be directly used for reinforcement of different strength and slenderness ratio with small error.

Abstract:In order to improve the mechanical property of the replaceable links in structural system with replaceable members, a novel type of the replaceable link with bolted end plate connection and end web stiffeners was proposed. The quasi-static test on two full-scale replaceable links was carried out and the finite element simulation analysis of the models was conducted using ABAQUS software to evaluate the influence of the stiffener configurations at the end of link flanges on the failure mode, bearing capacity, flange plastic strain. The test results show that all specimens yielded in shear, followed by two types of failure modes, i. e., web-to-stiffener weld tear and fracture at the flange-to-end plate welds, those of which showed a stable bearing strength and excellent energy dissipation behavior. Meanwhile, the specimen with end web stiffeners was effective in shifting plastic flange strains away from the flange-to-end plate welds to sustain ductile inelastic deformation and replaceability under cyclic loading. The finite element simulation results were in good agreement with the experimental results, which verified the validity of the finite element model. Feartures of the plastic strains of these modes indicated that five end stiffener configurations shifted flange plastic strains caused by link deformation away from the welds to strength the seismic performance. Finally, the proposed formula for the replaceable link with bolted end plate connection and end web stiffeners was recommended, and the feasibility of design method was verified.

Abstract:In order to reduce the crack or damage of the wall caused by the temperature difference between the inner and outer blades when the concrete sandwich slab is used as building envelope, the internal force and deformation of the concrete sandwich slab under the temperature action are studied. The internal and external blade connectors of concrete sandwich slab were homogenized, and the analytical solution of interfacial stress of concrete sandwich slab was deduced, assuming that the internal and external blade only produced bending deformation and the bending curvature of the internal and external blade were different. Thus, the theoretical calculation formula of the position of the most disadvantageous section of internal and external blade of concrete sandwich slab, as well as the internal force and deflection of internal and external blade were obtained, and the theoretical formulas were verified by the finite element software ABAQUS. The results show that the theoretical formula is in good agreement with the finite element analysis results, the internal forces of the most unfavorable section in mid-span of the inner and outer blades of partial composite concrete sandwich slabs have nothing to do with the stiffness of the connectors, and the maximum mid-span deflection increases with the stiffness of the connectors, but the increase is small.

Abstract:Aluminum alloy plate has the advantages of high strength, good ductility, good corrosion resistance, which can be used to strengthen concrete structures in damp, cold and harsh environments. However, the interface performance of aluminum alloy plate-concrete is the key factor which affect the effect of concrete reinforced by aluminum alloy plate. Based on this, the interfacial double shear tests of 48 aluminum alloy plate-concrete specimens were completed. The influence of bond thickness of aluminum alloy plate, bond length of aluminum alloy plate and structural adhesive type on the interface failure mechanism, interfacial peeling bearing capacity, bond shear stress and the slip evolution were analyzed. The results show that the peeling capacity of the interface can be effectively improved by increasing the thickness of the aluminum alloy plate, the bonding length of the aluminum alloy plate and using the structural adhesive with low elastic modulus, but the bonding length of the aluminum alloy plate should be controlled within the range of the limited bonding length. At the same time, with the increase of bond length, the slip of specimen increases, and the thicker the bond thickness of aluminum plate, the lower the slip of the specimen. Use double-line model, hyperbolic model, Nakaba model and test results for comparative analysis. The results show that the aluminum alloy plate-concrete bond slip is in good agreement with the curve of the Nakaba model.

Abstract:According to the basic principle of bridge indirect measurement, the finite element model of vehicle-bridge coupled vibration is established for a three-span continuous girder bridge. The time-history response of the vertical acceleration is extracted when the vehicle passes the bridge at a constant speed. The acceleration spectrum is obtained by using fast Fourier transform. The acceleration spectrum is obtained by using fast Fourier transform. The central difference method is used to calculate the time-history response of the contact point acceleration. The first three frequencies of the bridge are identified by the peak picking method. The bandpass filtering technology is used to extract the component response related to the bridge frequency from the vertical acceleration response of the contact points, the first three modes of the bridge are obtained by Hilbert transform. The identified mode shapes are compared with the finite element theoretical mode shapes. The results show that the change of vehicle mass has no obvious effect on modal identification. Although the low speed is unfavorable to the mode identification, the accuracy of mode identification can be ensured by selecting the appropriate speed. Based on the finite element model of the bridge, the mass of the identified modes is normalized, the test displacement flexibility matrix of the main girder is calculated, and the standard load test scheme of the bridge is designed. The flexibility matrix was used to predict the deflection of the main girder under the test load, and compared with the theoretical deflection. The results show that the errors of predicted deflection and theoretical deflection meet the requirements of engineering accuracy.

Abstract:Limited by the differences between cementitious materials and basic magnesium sulfate cement (BMSC), the study of enhancing the toughness and mechanical properties of BMSC products by incorporating bio-based fillers with fibers is still very limited. Through different mix design, wood fiber and basalt fiber (BF) were used as lightweight fillers and reinforcements of BMSC materials. The fluidity, dispersity (fiber), density, compressive strength and flexural strength of modified BMSC were tested. The typical samples were characterized by SEM, EDS and XRD. The results showed that the addition of wood fiber significantly reduces the density of BMSC, and the combination of wood fiber and BF can significantly improve the mechanical strength, especially the flexural strength, with the maximum increase rate of more than 80%. By microscopic characterization, it was found that wood fiber has good mixed compatibility with plant materials in BMSC. The combination of wood fiber and BF forms a magnesium cement matrix-wood fiber-BF model, which significantly improves the strength of the composite reinforcement. A semi-quantitative method based on image recognition technology was attempted, and it was found that the development degree of hydration products crystals could be analyzed quantitatively. It provides the possibility to control the performance of BMSC products during material preparation.

Abstract:A series of pollutant content tests of organic matter, total nitrogen, total phosphorus and heavy metals were performed on the river sediment and overlying water obtained from five sites in Jin'an District, Fuzhou. Partition coefficient was introduced to study the correlation of pollutants between the river sediment and overlying water. The correlation of pollutans between sediment and overlying water was analyzed by the distribution coefficients of organic matter, total nitrogen, total phosphorus and heavy metals. Then, introduced the relationship between the standard deviation of partition coefficient and correlation coefficient, discussed the correlation between pollutants in sediment and overlying water, and clarified its key influencing factors. The results show that the partition proportion of different pollutants in sediment and overlying water is different, and the correlation coefficient between pollutants in overlying water and sediment is quite different. The more stable the pollutant distribution coefficient is, the higher the correlation is with the pollutants in the overlying water. The clay content, organic matter content and plasticity index of sediment have a significant impact on the pollutant partition coefficient. The pollutant partition coefficient increases with the increase of clay content in the sediment, and the heavy metal partition coefficient increases with the increase of organic matter content in the sediment. The partition coefficient of organic matter and total nitrogen show an increasing trend with the increase of plasticity index. There is a good linear relationship between the logarithm of heavy metal partition coefficient and the plasticity index of sediment.

Abstract:With the development of industry, the industrial wastewater output has been increased over time. However, the refractory and toxic organic compounds in industrial wastewater restrict the treatment efficiency significantly. Based on the co-metabolism theory of microorganisms, the addition of readily biodegradable organic substrates has been successfully employed to improve the removal efficiency of refractory organic compounds. However, the readily biodegradable organic substrates used in practical wastewater treatment process mainly come from the artificial addition of commercial carbon sources, which would increase the operating cost and emit a large amount of carbon. Mixing some wastewater rich in readily biodegradable organic substrates with refractory organic wastewater may be a good strategy, which can not only improve the refractory organic treatment efficiency, but also realize the wastewater recycling. This paper reviews the characteristics and hazards of industrial wastewater, research statues of co-metabolism mechanisms, and focuses on the research and application cases of mixed treatment of wastewater, including food wastewater, textile wastewater, paper making wastewater, some pharmaceutical wastewater, domestic sewage and wastewater in the industrial park. Meanwhile, this paper proposes the prospects and challenges of wastewater mixed treatment, as well as its future development. The aim of this paper is to provide guidance for the wastewater mixed treatment technology application, green and low-carbon industrial park construction, in order to achieve green and low-carbon wastewater treatment.

Abstract:This study was conducted to study the impact of dissolved organic matter (DOM) composition on the efficacy of coagulation, UV Fenton and Electro-Fenton for removing organics in of leachate concentrate from two sources. The DOM removal differences of two kinds of leachate membrane concentrates were compared and analyzed. The dissolved organic carbon (DOC) removal rate of coagulation, UV Fenton, and Electro-Fenton processes were 42%, 66% and 62%, respectively for the 1# leachate concentrate (processed by "MBR+NF"), and were 20%, 60% and 52% respectively for the 2# leachate concentrate (processed by "A/O+RO"). Experimental results showed the different DOC removals between two leachate concentrate samples treated by the same processes. These differences were attributed to different DOM composition between two leachate concentrate samples as indicated by the combined analysis of excitation-emission matrices (EEM) with parallel factor analysis (PARAFAC) and liquid chromatography-organic carbon detector (LC-OCD). Compared the 2# leachate concentrate (52% determined by LC-OCD analysis), the 1# leachate concentrate had a higher percentage of high molecular weight (HMW) organics (73% determined by LC-OCD analysis) which were preferentially removed by coagulation and two Fenton-like treatment, thus achieving higher DOC removal rate. Furthermore, it is speculated that macromolecular organics transformation into low molecular weight (LMW) organics and the subsequent mineralization of low molecular weight (LMW) organics may occur during two Fenton-like oxidations. On this basis, it is suggested that coagulation or Fenton-like process can be used if the leachate concentrate containing large portion of HMW organics, a combined coagulation-Fenton-like process was proposed for a better DOC removal in the leachate concentrate containing a large portion of LMW organics.