Abstract:Setting a flexible pad cusion behind the rigid retaining wall can effectively reduce the lateral earth pressure. Expanded polystyrene (EPS) geofoam is a common flexible material that has the characteristic of easy compression. In this paper, through the retaining wall model test in laboratory, the lateral earth pressure distribution of different EPS boards with different elastic modulus and thickness is studied; the influence of elastic modulus and thickness on the decompression performance of EPS boards under different loadings on the filling surface is analyzed in detail. The influence of compression value of EPS board on the lateral earth pressure on retaining wall is also analyzed by FLAC^3D numerical modeling. The research results show that the EPS board can effectively reduce the lateral earth pressure behind the retaining wall; the smaller the elastic modulus of the EPS board, and the larger the thickness, as well as the external load on the surface of the backfill wall, the decompression effect of the EPS board becomes more significant. After the EPS board thickness increases to a certain extent, the decompression effect of the EPS board will not increase significantly. The best decompression effect can be obtained when the EPS board thickness reaches 0.1 times the wall height.

Abstract:In order to fully utilize the high strength of the cemented soil pile/wall, a retaining structure with soil nailing wall combined with cemented soil pile/wall for deep excavation is proposed and its design philosophy is discussed in this paper. Based on finite element numerical simulation combined with the typical geological condition of Nanchang area, the distribution characteristics of seepage flow, horizontal soil displacement, axial force of soil nail, stress of cement-soil pile wall and the failure mode as well as the influence of bottom reinforcement and cement-soil pile wall distance of the novel structure on the support performance are systematically studied. Meanwhile, comparative analysis with the traditional soil nailing wall structure and the composite soil nailing wall structure are conducted. The results show that: Under the condition of ensuring the safety of the wall, the support mechanism of the novel structure is more reasonable due to the horizontal displacement of the soil at the excavation face and the axial and tangential stresses of cement-soil pile wall much smaller than that under the traditional soil nailing wall structure and the composite soil nailing wall structure; the failure mode of the foundation pit is similar with that under the gravity retaining wall support method, and reinforcement of the pit bottom can significantly improve its support performance.

Abstract:Xigeda Formation is distributed in southwest of China, and its engineering properties are very poor. In order to analyze seepage characteristics and stability of silty sand slope of Xigeda Formation overlying Quaternary residual slope sediments under heavy rainfall conditions, seepage law of slope is studied by numerical simulation based on Mojiagang landslide in Shimian County; Morgenstern-Price method is used to calculate safety factor of landslide and to analyze their variation laws. The results show that: rainwater infiltrates into slope layer by layer, and seepage process will continue after rainfall. As the existence of soil layer interface, seepage characteristics are different from homogeneous slope; during the rainfall process, the range of pore water pressure growth accelerates near the interface, and the Quaternary residual slope sediments near the interface is still in a near-saturated state after the rainfall; rainfall infiltration leads to reduction of safety factor of the slope, and stability has a lag in response to rainfall.

Abstract:In the process of urban construction, shield tunnel excavation will pose a great threat to the adjacent existing pile under high-speed railway. Driving isolation pile between the tunnel and high-speed railway foundation pile can effectively reduce the influence of the shield driving to adjacent pile foundation. In the field of pile-soil interaction, Winkler foundation model and Pasternak foundation model have been widely used. Based on these two foundation models, this paper uses the finite difference method by Maple mathematical software to analyse a practical engineering case. The calculated results are in accordance with existing engineering monitoring data. Then the influences of isolation pile of various parameters on the horizontal displacement of the pile under high-speed railway are further analyzed. The results show that Pasternak foundation model is more accurate than Winkler foundation model when the elastic modulus of isolation pile is smaller. With the increase of isolated pile diameter, the horizontal displacement of pile foundation will decrease significantly. The horizontal displacement of high-speed railway pile foundation can be reduced by reducing the horizontal distance between the isolated pile and the tunnel center line on the condition that the parameters of isolated pile remain unchanged.

Abstract:The low embankment of the expressway is limited by the height of subgrade, and some special problems such as excessive settlement or uneven settlement are easily caused after construction. At present, the subgrade design and maintenance codes do not uniformly regulate the design of the low embankment, resulting in many problems that would affect the normal use of the structure during the construction and operation of the low embankment. Based on the risk assessment theory of geological disaster, this paper analyzed the effect of some factors such as drying and wetting cycle as well as traffic load on the low embankment of the expressway. In addition, considering the maintenance and repair, these factors were modified and the evaluation method of low-embankment-subgrade in service status was proposed. Combined with fuzzy comprehensive evaluation method and matter-element analysis method, the structural quality vulnerability in construction period, the risk of subgrade in operation period and the modified value of maintenance and repair were analyzed. And then the comprehensive risk of low-embankment-subgrade was obtained. The method was applied to a low embankment project in northern Zhejiang. The result shows that the comprehensive risk is low and the service state risk is basically consistent with the filed survey result, which illustrates the feasibility of the proposed evaluation method.

Abstract:In view of the problem that steel slag is prone to expand in base material, steel slag, blast furnace slag micro-powder and soil were mixed to prepare a road base material-steel slag mixed soil using soil solidification technology. The compaction, expansion rate and unconfined compressive strength tests were carried out on 16 soil samples with different mixture ratios. The results show that the optimum moisture content of the steel slag mixed soil is little affected by the mixture ratio, which maintained at 12~14%. The maximal dry density decreases with steel slag content, and decreases as the content of blast furnace slag micro-powder rises. Blast furnace slag micro-powder could significantly reduce the expansion rate of steel slag mixed soil and increase its unconfined compressive strength. The 7 d, 14 d, 28 d and 90 d unconfined compressive strength of steel slag mixed soil are firstly increase then decrease with steel slag content, and the strength reaches the maximum value when the mixture ratio is 50% steel slag and 50% soil. Microstructural analysis shows that the change of surface charge of soil particle enhance the compactness of steel slag mixed soil in molding process. The hydration reaction of f-CaO in the steel slag was inhibited during solidification, and which conduct digestion reaction with SiO₂ in the mineral slag to form hydrated calcium silicate gel (C—S—H). At the same time, inter-particle stacking effect between steel slag and soil and self-compacting effect produced by C—S—H gel could enhance strength of steel slag mixed soil, and thus steel slag mixed soil with high strength and stability is prepared.

Abstract:Based on the compression and swelling curves at different temperatures, the thermal consolidation phase is substituted by a mechanical consolidation phase, which is of the same deformation. Then, the complex thermomechanical properties of soils have been translated into pure mechanical properties. Further, a new non-associated elastic-plastic consititutive model considering temperature effects is presented by using the traditional critical state theory and non-associated flow rule. The whole model contains six independent parameters, and the physical significance of each parameter is specific and easy to be confirmed through the temperature-controlled triaxial compression test. In addition, with an increase in temperature, the slopes of the compression and swelling curves, the critical state stress ratio and poison ratio have no obvious changes, while the preconsolidation pressure changes exponentially. Otherwise, the trial method is used to determine the scaling factor between the plastic potential and yield equations. Finally, the method of determining each model parameter is put forward in detail on account of the drained temperature-controlled triaxial test for Kaolin and Bourke clays, and the new model is proved to be reasonable by comparing the simulation values and test data.

Abstract:The deformation characteristics of rock mass and the coefficient of subgrade reaction are directly related to the internal force, final deformation and deformation uniformity of foundation. Determination of reasonable coefficient of subgrade reaction is important for high-rise buildings, especially super high-rise buildings. Taken a super-high-rise building in Chengdu as example, plate loading tests of red-bed soft rock foundation with different plate sizes and shapes were carried out. Besides, the uniaxial compressive strength test (UCS), conventional triaxial compression test and direct shear test of red-bed mudstone were carried out. Based on the results of laboratory and in-situ test, the relationship between UCS, elastic modulus, bearing plate size and coefficient of subgrade reaction were analyzed. The results show that the coefficient of subgrade reaction has a tendency to increase with UCS of rock, and the smaller the bearing plate size is, the more discrete test data will be obtained. The coefficient of subgrade reaction of red-bed mudstone obtained by 500 mm square bearing plate test is recommended. It is found that the coefficient of subgrade reaction of red-bed mudstone layer has a hyperbolic empirical relationship with the plate size. If the coefficient of subgrade reaction of red-bed mudstone layer is modified according to the empirical formula of clay or sand recommended by the code, it will cause a large error. Therefore, it is suggested that the coefficient of subgrade reaction is modified based on the hyperbolic empirical relationship.

Abstract:The effects of cracks (soil disengagement) and grouting time at the interface between slab and soil on the osmotic consolidation process of soft soil were studied through one-dimensional electroosmosis consolidation test. The "grouting time" control test was performed by injecting CaCl₂ solution and Na₂SiO₃ solution in a tight sequence. Based on the combined effects of "precipitation or colloid" and "ion" on electroosmosis consolidation, the variation of current, drainage, soil moisture content and shear strength, cracks and body shrinkage and energy consumption of electroosmosis with grouting time were studied. The test results show that cracks at the interface between slab and soil (slab detachment) always occur before other parts, and the sharp decrease of current value caused by slab detachment is the main reason of the reduction of electroosmotic effect; During the consolidation process, there is a time t_cr for the fast development stage of crack at the slab-soil interface. Using t_cr as the indicator to determine the optimal grouting time can achievethe best electroosmosis effect. In order to prevent the obvious abrupt change of water content in the soil, it should be noted that the grouting time should be not earlier then 1/3 t_cr, and grouting at 2/3 t_cr can achieve the best electroosmotic consolidation effect.

Abstract:Microbial induced calcium carbonate precipitation (MICP) cemented remolded mudstone samples were prepared by injecting one-time bacteria solution with different concentrations (0, 0.3, 0.5, 0.7 mol/L) of nutrient salt treatment. Based on the results of direct shear test, calcium carbonate pickling and scanning electron microscopy (SEM), the effects of nutrient concentration on the mechanical properties, calcium carbonate content and microstructure of the cemented samples were analyzed. The results show that under the same reaction conditions (same time, volume), the shear strength increase at first and then decrease with the increase of nutrient concentration. When the nutrient salt concentration reaches 0.5 mol/L, the shear strength reaches the largest value. At this time, the cohesive force and internal friction angle of the sample are 15.5 kPa and 18.83°, respectively. The content of calcium carbonate increase with nutrient concentration. When the concentration of nutrient salt reaches 0.7 mol/L, the average calcium carbonate content of the sample increases less. The uniformity of calcium carbonate crystal distribution changes in a convex shape with the increase of nutrient salt concentration from low to high. The strength of the cemented sample depends on the amount of CaCO₃ crystals formed and their distribution. The produced calcite-type calcium carbonate crystals are mainly deposited at the contact position of the particles to form accumulated crystals or filled in the pores to form a "bonding bridge", which produces a cementation effect and enhances the mechanical properties of the sample.

Abstract:Pendulum eddy current TMD as a new type of damper is often used in the control of human-induced vibration and wind-induced vibration, but seldom used in seismic engineering. And there is still a lack of effective calculation methods. In this paper, a coupling calculation method based on joint simulation is proposed to investigate the damping performance and reasonable value of mass ratio. A numerical model is established for 5-story, 10-story and 20-story steel frame structures along with five groups of pendulum eddy current TMDs with different mass ratios, which conform to the current Seismic design code for buildings and mechanical properties of pendulum eddy current TMD. A dynamic time-history analysis is performed on the numerical model by using coupling calculation method. The analysis yields a series of curves of story drift, interstory drift ratio, story shear force, and story acceleration versus mass ratio under rare earthquakes. The analysis results are compared to the results of the control model that has no pendulum eddy current TMD. The comparison shows the feasibility of the proposed coupling calculation method and that pendulum eddy current TMD can effectively reduce the seismic response of the steel frame, with a 26.5% reduction for story drift, 20.9% for interstory drift ratio, 4.3% for story shear force, and 7.3% for story acceleration of a 20-story steel frame structure when the reasonable mass ratio is recommended to be 3%.

Abstract:Concrete tube filled reactive powder is a new type of constained composite column based on ultra-high performance cement casing, with the mechanical properties of reactive powder concrete and the constraint effect of stirrup. In this paper, four Concrete-Filled RPC Tube (CFRT) columns and one ordinary hoops-confined concrete column were tested under cyclic and constant axial load. The failure mode, hysteresis behavior and strain development of reinforcements were investigated, and the relevant seismic parameters were analyzed. CFRT columns exhibited typical bending failure characteristics. In contrast to conventional reinforced concrete column, the surface of Reactive Powder Concrete(RPC) tube was characterized with well distributed fine cracks, without any RPC cover spalling or crushing. The hysteresis curve of CFRT cloumn is full, and its seismic performance is significantly better than that of ordinary stirrup confined concrete cloumn. Under the test conditions, the limit plastic drift ratios of CFRT columns vary between 0.042 and 0.075, which largely exceed the specified limit (0.02) according to the rare earthquake requirement in Chinese seismic design code. The results also reveal that RPC tube filled with high strength concrete is an acceptable combination for CFRT columns.

Abstract:In order to reduce the bond degradation of beam reinforcement bars in beam-column exterior joints with HRB600 reinforcement bars, the beam-column exterior joints with overall or local steel fiber concrete were designed. The low-cycle loading tests were carried out on two ordinary concrete beam-column exterior joint with HRB600/HRB400 reinforcement bars, and two steel fiber concrete beam-column exterior joints with overall or local steel fiber concrete and HRB600 reinforcement bars. The failure modes, hysteresis curves, energy dissipation, ductility, shear deformation in the core zone and bond degradation of beam reinforcement bars were analyzed. The research results showed that the joints with HRB600 reinforcement bars exhibited higher bearing capacity, energy dissipation capacity and ductility under low-cycle loading, but the bond degradation between HRB600 reinforcement bar and ordinary concrete degraded too quickly. The exterior joint reinforced by overall or local steel fiber concrete exhibited slower bond degradation of HRB600 beam reinforcement bars, slighter failure mode, smaller shear deformation in the joint core area, and larger energy dissipation capacity. The beam-column exterior joint with overall steel fiber concrete had higher ductility and energy dissipation capacity compared with the beam-column exterior joint with local steel fiber concrete, and the bond degradation of HRB600 beam bars was slower.

Abstract:The theoretical and experimental researches on the bond interfacial shear stress of the RC beams strengthened with aluminum alloy plate (AAP) were carried out, in order to provide basis for the connection design between AAP and RC beam. It is assumed that the shear deformation of structural adhesive changes linearly along the thickness direction. Then the general solutions of the interfacial shear stress of the RC beam strengthened with AAP without anchorage under general loads were obtained according to the displacement coordination condition of the bonding interface. The analytical expression and maximum value of the interfacial shear stress under several common loads were given. Considering the influencing factors such as the thickness of AAP and U-wraps connection, 6 RC beams strengthened with AAP were designed, and the three-point loading tests of simply supported beams were carried out. Based on the relationship between the normal stress and the interfacial shear stress of the AAP, the interfacial shear stresses of the AAP were got by the strain gauge densely attached to the longitudinal axis of the AAP. According to the theoretical and experimental results, the interfacial shear stress distribution curves and the maximum interfacial shear stress were obtained. The results show that the theoretical and experimental results of the interfacial shear stress distribution curves are in good agreement, showing the same change law: the interfacial shear stress quickly falls to the vicinity of the horizontal axis after reaching the maximum at the plate end. After the crack appears, the curve fluctuates at the crack. As the thickness of AAP and the distance between plate end and support become larger, the interfacial shear stress becomes also greater, the thickness of structural adhesive becomes larger, the interfacial shear stress becomes smaller, and setting U-wraps connection, the interfacial shear stress becomes smaller.

Abstract:In order to reduce the influence of vehicle loads on the vibration of building structure, a new type of steel spring floating slab vibration isolation road was designed, and the dynamic design parameters of floating slab were studied. On the basis of finite element test verification of the scale model of floating slab, four parameters were selected and orthogonal tested, including length and thickness of floating slab, spring stiffness and support spacing. Total of 81 cases of corresponding 3D finite elements were established. The modal analysis method was used to study the influence of various parameters on the natural frequency and vibration mode of the floating slab. The traffic load excitation was measured, and the response of the floating slab structure in the time domain and the frequency domain was analyzed, and the vibration damping effect of each parameter of floating slab structure is discussed by Z vibration level and insertion loss. The results show that the fundamental frequency of each sample is mainly distributed between 4 Hz and 10 Hz. The fundamental frequency directly affects the vibration isolation performance of the steel spring floating slab. With the decrease of the length, the increase of the thickness, the decrease of the stiffness of the spring and the increase of the spacing of the supports, the isolation effect of the floating slab structure is obviously improved. The vibration amplification frequency band of the floating slab structure is located near the fundamental frequency and in the range of 14~18.0 Hz under the traffic load excitation. The VL_z vibration level increases with increasing frequency in the range of 0~18 Hz, and then decreases with increasing frequency, but does not exceed 72 dB. For the vibration response within the range of 0~40 Hz, the maximum amount of vibration reduction in all samples is 40.6 dB, and the maximum amount of emission at the fundamental frequency is 17.4 dB.

Abstract:Based on the theory of the axial tension modified Timoshenko beam model, this paper studies the dynamic characteristics of the cable substructure from the perspective of waves, and discusses the near-field wave and traveling wave separately. The effects of near-field waves can be ignored when it near the beam end or at high frequencies. Based on the travelling wave propagation characteristics in the beam structure, the wave component coefficients were obtained by the least square fitting method, and then the cable force and bending stiffness were identified with the aim of minimizing the fitting residual. Subsequently, the accuracy of the method was verified by numerical simulation experiments of cable vibration, and the error of cable force identification did not exceed 1%. Compared with the traditional frequency method, this method is based on the substructure cable force identification, which is not affected by shock absorbers and boundary conditions. Furthermore, the identified sub-cable segment cable forces can be used to inversely push the cable forces at various locations through static analysis. At the same time, the corresponding cable force can be identified at each frequency sampling point, reducing the impact of external interference on cable force identification.

Abstract:Large scale reinforced concrete aqueduct, as a lifeline hydraulic structure, the reliability of its water transport function is very important. However, on one hand, the mechanical property of concrete is equipped with remarkable randomness and nonlinearity. On the other hand, the aqueduct structures may inevitably suffer from uncertain disastrous earthquake actions during service life, posing a great threat to their service safety. To these ends, the present paper proposed a quantification framework for the water-conveyance reliability assessment of the aqueduct structures by incorporating the stochastic damage mechanics model of concrete and the probability density evolution method. The principle and implementation procedures of the developed framework were illustrated in detail on an actual large-scale RC aqueduct structure. The results show that the probability density evolution theory can accurately and efficiently evaluate the reliability of aqueduct structure water conveyance function. The water-conveyance reliability varies with the change of pre-defined seismic fortifications, which should be reasonably accounted for in early design phases.

Abstract:The slab diffusion model based on semi-infinite slab element is usually used to estimate the time to corrosion initiation of RC (reinforced concrete) circular column exposed to coastal atmosphere zone, which ignoring the effect of the circular across-section. The diffusion model considering the diffusion coefficient as time-dependent variable and the effect of circular across-section shape, the influence of the shape of circular RC column exposed at coastal atmospheric zone on the corrosion initiation time is analyzed. The results show that with the coastline increasing and the radius decreasing the overestimation of the corrosion initiation time by using the slab diffusion model is the more obvious. A model for calculating the bearing capacity of corroded reinforced concrete columns is presented, the effect of the radius value on evaluating the degradation rate of bearing capacity of the column at coastal atmosphere zone under different service periods is further discussed. The research results show that the increase of radius result in the reduction of the influence of corrosion on bearing capacity. In the scenario of the RC column located at heavy salt fog zone, the slab diffusion model can be directly used to evaluate the corrosion time. However, in order to control the degradation rate difference value caused by using slab diffusion model within 5%, the effect of shape on corrosion initiation time should be considered when this column is exposed to the light salt fog zone and the radius is less 60cm. And the residual bearing capacity of RC circular column with different service periods is further evaluated.

Abstract:One of the key points for developing ultra-high performance concrete(UHPC) with good construction is to determine the suitable water-binder ratio. Based on the premise that the typical raw materials and mix ratio of 150MPa grade UHPC remained unchanged (except water consumption), the influence of water-to-binder ratio (0.15~0.2) on the construction and mechanical properties of UHPC were studied. Through relevant tests, the extension degree, compression resistance, bending strength, four-point bending stress-deflection curve, and equivalent tensile stress of UHPC under different wet mixing time (full wet mixing time, static stop for a period of time) were obtained. Subsequently, the variability of compressive strength and flexural strength results were analyzed; Using the stress-deflection curve, the index of bending toughness was obtained based on the standard method. At the same time, an improved method for calculating flexural toughness index of UHPC was proposed. The test results show that the full wet mixing time of UHPC is 6 min. The extensibility of UHPC increases linearly when the water-to-binder ratio increases from 0.16 to 0.19. And at this time,the average extensibility rate of UHPC increases to 109 mm with the water-to-binder ratio increases by 0.01. The extensibility loss of UHPC is 40mm, and the loss rate is only 5.9%, when the water-to-binder ratio and standing time are 0.19 and 4h. The compressive strength, flexural strength and flexural toughness index of UHPC all increase first and then decrease with increasing of water-to-binder ratio, and when the water-to-binder ratio is 0.18, 0.16 and 0.16 respectively, the three mechanical properties reach the best. The stress-deflection curve before the stress peak is an atypical full convex curve. The strength of visible first crack is about 0.85 times that of flexural strength. The flexural toughness of UHPC is good, so it is better to use visible first crack deflection as the initial deformation reference to calculate the flexural toughness index. In order to ensure the good construction and mechanical properties of UHPC, the wet mixing time and water-to-binder ratio should be 6min, 0.18 or 0.185 respectively.

Abstract:The bi-periodic trapezoidal corrugated plate is a new type of lightweight structure with periodic trapezoidal corrugated changes along two plane directions. At present, there is little research on the relationship between its mechanical properties and structural parameters, limiting the popularization and application of this structure. In this article, a numerical model of the represent element (or called unit cell) is established by using the variational asymptotic method to calculate the equivalent stiffness. Then, the bi-periodic trapezoidal corrugated plate is converted to orthotropic plate with the same stiffness characteristics by homogenization technology. Based on this method, the equivalent stiffness with different structural parameters, global deformation and buckling modes are calculated, and the accuracy of the equivalent model is verified by comparing with the three-dimensional finite element simulation results. The results show that the equivalent stiffness of the bi-periodic trapezoidal corrugated plate is lower than that of the plate due to the change of the shape, and the bending stiffness is increased. The tensile stiffness increase and the bending stiffness decrease with increasing interval length and decreasing plate height. While with the increase of plate thickness and web length, the bending stiffness shows an upward trend. The constructed model is suitable for the case that the period of corrugation is far less than the structure size. The approximate energy of the equivalent plate model is as close as that of the original three-dimensional corrugation plate, which is guaranteed by the asymptotic expansion analysis of the leading terms of energy functional. The equivalent plate model can be used to calculate the equivalent bending moment and the equivalent maximum tensile/compressive stress of corrugated plates with different material properties, which can effectively reduce the calculation amount and save the calculation resources.

Abstract:Treatment of micro-polluted water is considered to be a vital issue and has attracted more and more attentions around the world. The turbidity and humus affect the quality of drinking water. As a widely used type of water treatment technology, coagulation is known for safety, practical and high-efficiency, and has been considered as a prospective technology for micro-polluted water. Coagulants are the core of coagulation technology and choosing a suitable coagulant to achieve high coagulation efficiency in the treatment process is crucial. Different kinds of coagulants, coagulants containing aluminum such as aluminum sulfate (AS) and polyaluminum chloride (PAC), coagulants containing ferric such as ferric chloride and polyferric chloride (PFC) were applied, and then followed by compound of coagulant aid polyacrylamide (PAM) and activated silicic acid (ASI) respectively. These coagulant aid possess good adsorption bridging ability and can improve the flocculation efficiency greatly to a certain extent. And in this work, turbidity, UV₂₅₄ and floc size were investigated to indicate the coagulation efficiency. The optimum coagulation conditions are determined as follows: AS dosage of 22 mg/L, PAC dosage of 18 mg/L, FeCl₃ dosage of 16 mg/L, and PFC dosage of 8 mg/L when used alone. PAM dosage of 0.1, 0.1, 0.05, 0.2 mg/L respectively when compounded with PAM. ASI dosage of 0.5, 1.5, 1.0, 1.0 mg/L respectively when compounded with ASI. In general, large amounts of humic acid are produced by the degradation of organic matter for aquatic organisms, and as a result, the water quality are seriously endangered. Thus, the removal of humic acid from wastewater has become imperative. In the passage, two common coagulants, PAC and PAM were applied in the treatment of humic acid wastewater, and PAC compounded with PAM was explored too. Same as before, the coagulation effect was determined by the measure of turbidity and floc size. The result shows that the optimal coagulation efficiency is achieved with PAM dosage of 8 mg/L, PAC dosage of 100 mg/L respectively when used alone. PAM dosage of 0.8 mg/L when compounded with PAC. The result shows that the compound can effectively enhance the coagulation effect at low dosage.

Abstract:In order to evaluate the impact of mining activities and ecological restoration measures on soil heavy metal pollution in antimony mining areas, the pollution status and regional characteristics of Sb, As, Pb and Cd in soils of different land properties among smelting area, road nearby ore, mining area and ore tailing area of antimony mine area in Xikuangshan, Hunan were studied, in addition, the ground accumulation index method and the potential ecological risk index method were used to evaluate pollution and ecological risk. It was found that the average contents of Sb, As, Pb and Cd in soil samples in the study area were 3 619.38 mg/kg, 82.20 mg/kg, 244.28 mg/kg and 30.84 mg/kg respectively, and heavy metal compound pollution were serious, the accumulation index method and the potential ecological risk index method indicate that Sb and Cd pollution in antimony ore area is serious, As, Pb has mild to moderate pollution, comprehensive has a strong ecological risk, among which Sb and Cd are the most important pollution factors. Significant regional characteristics was showed by the heavy metal concentration in soils among each areas because of mining activities such as smelting, mining, transportation and stacking; the content of Sb in soil samples decreased successively in residue-field, wasteland, forestland, sediment, grassland and vegetable-field, which indicated that the method of grassland ecological restoration was an effective method to control soil antimony pollution.

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