Abstract:When crossing active ground fissure diagonally, subway tunnel is in the complex stress state of bend, shear as well as torsion. According to outstanding torsional deformation and failure of physical model test for box tunnel, based on the theory of thin-walled under constrained torsion and combined with box tunnel diagonal crossing active ground fissure of the actual stress situation, the torsion angle and shear stress analytical solution of box tunnel lining structure under concentrated torque and uniform friction torque on surface were proposed. By using ANSYS, box tunnel lining structure and torsion deformations finite element model was established. And the torsion angle cross-section and the maximum shear stress were analyzed. The torsion angle and the maximum shear stress from the result of numerical simulation and analytical were in good anastomosis.

Abstract:Unloading of excavation of foundation pit has influence on adjacent tunnels, therefore it is important to predict the deformation of metro tunnels to ensure the operation of tunnel. The displacement effect due to the surrounding wall soil unloading of adjacent excavation was not considered by the theoretical analysis method, and the analysis procedure of FEM was usually too complicated to get a satisfied result, so the horizontal and vertical additional stress were calculated by the Mindlin solutions. Furthermore, the tunnel structure was considered as the beam with infinite length. The additional stress was imposed on the Winkler model and the governing equation was built up on the adjacent tunnel structure. Finally, displacements and internal forces of existing tunnels were obtained. Compared with the numerical simulation and an engineering case, the results of the presented formula are in good agreement. It can provide certain theoretical and calculation basis for metro tunnels influenced by adjacent excavation.

Abstract:As for many lagged surface collapse cases that shield crosses the sandy cobble stratum in Chengdu metro No.1 and 2 lines, lagged surface collapse mechanism in sandy pebble stratum was studied. Conditions of engineering geology about sandy cobble stratum were analyzed. Mechanical behavior of sandy pebble was obtained via large-scale tri-axial test. Discrete element method was adopted for numerical computation on lagged surface collapse mechanism. According to the tri-axial numerical test method, the relation between the micro parameters and macro parameters of the sandy pebble stratum layer in Chengdu was calibrated. The face failure of shield tunneling and upward movement of cavity was simulated by numerical calculation. When supporting pressure is small, the particles with the displacement of over 0.1 m have low contact force. The porosity of earth in the region becomes larger and its mechanical behavior becomes worse. Therefore the region can be identified as instability region. Cavity in the ground will be caused after shield tunneling. Soil arching effect is obvious under shield construction. Even though there is cavity in the ground, surface collapse will not bring about immediately. This is important reason for lagged surface collapse phenomena of shield construction in sandy pebble stratum.

Abstract:Soft clay is stabilized by desulphurization gypsum and steel slag-slag blended cementitious materials (GSC), which can not only reuse industrial waste and decrease second pollution, but also can conserve mineral resources and protect natural ecology. The variation of unconfined compressive strength of the clay improved by GSC with different mixing ratios and water-GSC ratio and ages was studied through the laboratory experiments. The long-term strength of stabilized soil is predicted with GSC by quasi-water-GSC ratio. The results show that the more the mixing ratios is, the better the stabilized effect of soft soil is. With increase of curing period, the strength increasing of GSC-soil is consistent with cement-soil, and it has lower strength in the early stage. When mixing ratios of GSC is more than those of cement by 3%, if the water-GSC ratio is less than those of cement, it has the higher strength than cement-soil, after 28 days. The results show that GSC stabilized soil is feasible and it can meet the demand of cure strength.

Abstract:Ventilating vacuum method can overcome the clogging problem which often occurs on the traditional vacuum method dewatering dredged clays with high initial water contents. However, how to analyze the anti-clogging behavior of ventilating vacuum method is an important issue in practical engineering. A radial drainage model was established based on the filtration theory developed by Ruth. The vanity of the model was verified using the test results of ventilating vacuum, and the change law in average radical dewatering resistance of dewatering layer which reflects the filtration performance was investigated during the dewatering process. It is indicated that the dewatered layer is compacted by traditional vacuum method during the dewatering process. Its corresponding pore structure is unstable, thus the drainage pipeline often clogs. While the technique of ventilating vacuum provides a powerful way to overcome the clogging problem, and the pore structure is stable during the dewatering process.

Abstract:Based on the interaction of single pile, cap and soil, the load transfer matrixes of single pile and soil were proposed to establish an equivalent shear displacement method of single capped pile in layered soil. With the compatibility of displacement at the interface between the pile and the soil, equilibrium equations of pile and soil could be derived. With the increase of the total load on the pile cap, the lateral friction at the interface of the pile and the soil becomes so large that the occurrence of the sliding takes place. While there is little sliding at the interface between the soil under cap and the soil outside of the cap because of the less lateral friction, which gives rives to less settlement of the soil outside of the cap. Eventually, the results of the finite element method, existing theoretical method and the model tests were compared with those from the analytical method and were found to be in good agreement. The increase of the ratio of length to diameter does not infinitely enlarge the overall stiffness of the single capped pile, because the pile cap would afford part of the loading all the time.

Abstract:In order to analyze seepage feature and seepage failure mechanisms of seawall under flood infiltration, a numerical model for saturated-unsaturated and unsteady seepage flow analysis considering soil permeability variation with seepage failure process was established. And the corresponding finite element computation program was made. Numerical simulation of flood seepage for typical section of real seawall was carried out by use of the program. The computed results were compared with the measured results of field test, which shows good agreement. Based on the numerical simulation results, it can be seen that flood seepage of seawall is a saturated-unsaturated and unsteady seepage flow process and seepage failure of seawall is caused by long time flood infiltration under large seepage gradient. Therefore, upon the flood infiltration, seepage failure of the seawall is a very complicated process, which involves soil permeability variation with seepage failure process and saturated-unsaturated/unsteady seepage flow. It is questionable to use the steady seepage analysis method to simulate seepage failure process of seawall.

Abstract:By operating an anaerobic degradation experiment of municipal solid waste landfill, the effects of periodic leachate emission, rainfall infiltration and full leachate recirculation on biodegradation process in landfill were investigated. And the control measures of water migration in biogas resources landfill were discussed. The results show that: in the case of leachate emission, it is difficult to form the suitable environmental factors of Eh, pH and humidity for methanogens. Rainfall infiltration plays a faint adjective function on microbiology environment. Under the continuous erosion action of infiltration rainfall, cumulative net CODCr leaching load increases by 67.8%. Leachate recirculation causes its cumulative production and net COD Cr leaching load decreases by 70.9% and 88.5% respectively, which shows an obvious inhibited effect on microbial metabolism at 15±2℃. With the temperature increases to 35±2℃, methanogens-suitable environment forms rapidly, but it causes the rapid accumulation of NH4 +-N in leachate. The measures, such as reducing the infiltration volume, controlling recirculation temperature reasonably and dealing with nitrogen removal before recirculation, can significantly improve the harmless and resources level of landfill disposal.

Abstract:In order to find out the reason of many “tiankeng” in southwest of china in recent years, based on seepage damage theory, the theory of saturated soil seepage and changed water head equipment were used to simulate the change process of water head in geologic norm, considering the influence of vacuum erosion as well. At first, physical property and chemical composition of soil samples were got by in-situ test and laboratory test before destroy test, and the result shows that the surface subsidence is not caused by carbonate karst cave. Then changed water head equipment was designed to simulate the change process of water head automatically. The gradation, water head and sample deformation characteristic of soil before the destroy experiment were compared with those after the destroy experiment. It is show that soil sample chemical property changes little, but little soil particles reduce significantly. With the change of gradation and structure of soil, the bearing capacity decreases and eventually it leads to the soil mass collapse. The changed water head test clarifies the reason and mechanism of “tiankeng” phenomenon reasonably.

Abstract:Eight specimens were tested under pure bending to investigate the overall buckling behavior of stainless steel welded I-beams, and the main parameter varied in experimental study was slenderness ratio. The test specimens were fabricated from cold rolled plate of austenitic stainless steel type 316. The material properties were determined by tensile coupon tests. A non-linear finite element model is developed and verified against test results. Initial imperfection and material non-linearities were included in the finite element model. In addition, the buckling strength of test specimens were compared with the design method proposed in the previous research. It is shown that the finite element model closely predicted the overall buckling strength and load-deformation curves; the design method was proved to be safe.

Abstract:In order to improve seismic performance of steel frame with prefabricated reinforce-concrete infill shear walls (SFCW), the ear bar device was used in the connection between the steel frame and the infill wall. Two one-bay, two story and one-third scaled models of SFCW were tested with low cyclic load. The working performance of ear bar connection, the cracks development in infill walls and deformation performance of SFCW were investigated. And the failure mode, hysteretic behavior,stiffness degradation,deformation and ductility and energy dissipation of composite structure were analyzed. The comparison study of steel frame with prefabricated, cast-in-place and silt reinforce-concrete infill shear walls was carried out. The results show that no failure occurs in the connection between the steel frame and the infill wall because ear plates below and up the beam-to-column connections are added in the specimens, and the connection device of ear plate presents good working performance. The properly designed SFCW has good ductility.

Abstract:The experimental and numerical investigations on buckling behaviors of aluminum alloy components with different irregularly shaped sections were carried out. The buckling load carrying capacity obtained through experiments, numerical simulations, and equations described in the design code were compared. Results obtained through experiments and numerical simulations in good agreement, which shows the validation of the numerical model. And the validated FEM model will be used for parametric analysis of buckling behavior of irregularly shaped aluminum alloy structural component. Equations in the design code do not include effects of the buckling type and need to be improved further.

Abstract:According to concrete box beam which flanges depth varying along the orientation of cross section, using variational principle of potential energy, new analysis method of shear lag is proposed for single cell concrete box beam. For simply supported girders and cantilever girders, general analysis of varying flange-depths influence on positive and negative shear-lag effect and deflection have be done. It's shown that varying flange-depths have influence both on sectional stress and deflection. Considering the varying flange-depths have effect on the calculation results of up to 15%.

Abstract:The design method of parameter optimization of nonlinear viscous dampers for dissipation structure was analyzed based on response surface methods. The method included experimental design, finite element analysis, fitting the response surface function and parameter optimization. Taking a reinforced concrete frame structure for an instance, the mathematical model of parameter optimization of viscous dampers for dissipation structure was established by taking the minimum all damping force as objective function and taking the interlayer maximum displacement less than limits as constraints, and then the damper parameters were optimized using the method of nonlinear programming optimization. The results show that the method of parameter optimization of viscous dampers based on response surface method can ensure the structural displacement is less than limit and the construction cost can be reduced.

Abstract:Seismic responses of power transmission tower-line system under multi-component excitations were analyzed by numerical simulation. A three-dimensional finite element model of transmission tower-line coupled system considering the geometric nonlinearity of transmission line was established. Twelve seismic records of different soil types were selected based on Code for Design of Seismic of Electrical Installations. Seismic responses of power transmission tower-line system under single component, two horizontal component and multi-component excitations were investigated using nonlinear time history analysis method, respectively. The results show that the responses of transmission tower-line system under multi-component excitations are significantly larger than those under single component excitation only, especially for considering vertical ground motion excitation only, and neglecting multiple nature of ground motion in analysis will underestimate the responses of the structure. To obtain an accurate seismic response and a better seismic design of transmission tower-line system, multi-component ground motion inputs need to be considered. The results provide reference for seismic design of transmission line practical engineering.

Abstract:In order to better understand the seismic performance of the hybrid structure, numerical analysis and shaking table model testing were conducted on a real tall building constructed in Beijing. The nonlinear analytic model of the structure was established with the aid of PERFORM-3D program, and the elastoplastic time-history analysis was performed. From displacement responses and energy dissipation of the entire structure, and deformations and plastic hinge forming condition of components, the response features under different earthquake levels were obtained. Based on the predetermined allowable limits of performance indices, the seismic performance of the structure was evaluated. In the mean time, the numerical analysis results were compared with test results. Both of test results and numerical analysis results indicate that the hybrid structure has good seismic performance.

Abstract:A non-destructive method of evaluation of specific crack area was used to characterise microcracking in concrete prisms during uniaxial compression loading and unloading. Chloride profiles were also measured after the same concretes were exposed to chloride environment. The relation among microcracking, stress-strength ratio and chloride penetration of concrete were analysed based on the experimental results. Under compressive load, the apparent chloride diffusion coefficient decreases until about one third of the ultimate load. Further increase of compressive load improves the chloride diffusion coefficient again. There is a close link between microcracking and stress-strength ratio. The index of specific crack area can be used to indicate the microcracking and study chloride transport behaviour into concrete under the influence of microcracking.

Abstract:Owing to the randomness of shrinkage and creep of concrete, random analysis method should be adopted to give a reasonable result with probabilistic guarantee. Stochastic variables for long-term analysis with GL2000 model about creep and shrinkage of concrete were presented. Combining Monte Carlo sampling with the response surface method, the stochastic analysis model was performed which is on time-variant deflection of prestressed concrete bridge. The long-term deflection of a prestressed concrete bridge was analyzed by this model. Sensitivity analysis and parametric study were carried out. And the uncertainty of creep model, elastic modulus of concrete, magnitude of sustained load, and prestress forces are the most important factors for long-term deflection. Furthermore, controlling accuracy of prestress forces and delaying the loading time are helpful to inhibit long-term deflection.

Abstract:The relationship between the bending strength and the size of Chinese larch visually-graded lumber was investigated. 1,961 pieces of lumber with three different widths were divided into two groups of high visual grades and low visual grades. The ultimate bending strength was tested under test spans of 18 times test depths. The combined length and width size effects of 5th percentile of bending strength were estimated by the slope method and the parametric method. Using the slope method, the estimated effect parameters of H and L were 0.19 and 0.23 for the 5th percentile.

Abstract:In order to analyze the nitrogen removal performance of anaerobic-aerobic process treating landfill leachate, a system combining ASBR with pulsed SBR was applied to treat real landfill leachate with high concentration of ammonia nitrogen. The HRT of ASBR was 2 d; middle water tank regulated the COD/NH +4-N (3～5) and NH +4-N concentration of pulsed SBRs influent; the cycle of pulsed SBR consisted of four anoxic stages and three oxic stages in which three equal feeds model was applied. In the fourth anoxic stage (An4), internal carbon source was used to implement denitrification without any extra carbon source addition. The results indicate that efficient nitrogen removal performance of this system was achieved in the series running period (157 d). Influent chemical oxygen demand (COD) concentration of ASBR was from 7 338 mg·L -1 to 1 0445 mg·L -1 of which above 83% was removed; pulsed SBRs influent NH +4-N concentration could be divided into four phases in which improving from 296.1±14.5 mg·L -1 to 912.0±41.7 mg·L -1, and the effluent total nitrogen (TN) concentration of pulsed SBR was below 40 mg·L -1 all the time, which means TN removal rate reached over 90%. To sum up, the COD and TN removal rate of the combined system were above 87% and 97%, respectively. Endogenous denitrification rate(DNR) of An4 changed from the fast one to the slow one, and the mean value of theoretical denitrification rate (TDNRm) of pulsed SBRs An4 could reach 1.531 mg N·h -1·gMLVSS -1. Advanced nitrogen removal of the system was realized without extra carbon source addition and physicochemical pre-treatment.

Abstract:Biofouling has become the focus of RO in water and wastewater treatment. Experimental investigation of RO biofouling mechanism and characteristics in wastewater advanced reuse was carried out by static test and cross-flow dynamic test on a lab-scale membrane fouling simulator(MFS).The experimental results show that the major contributors to biofouling are coli and filamentous bacteria; there usually is no biofouling on the RO membrane surface with the absence of microbial source and nutrient composition; it is easy to cause biofouling on the fouled membrane; the germicidal treatment and the protection in the shut-down period are important for RO. Guidance for the analysis and reduction of biofouling in the practical engineering is provided.

Abstract:Firstly the impacts of heating temperature and rate of microwave on dewater ability and morphological feature of sewage sludge were investigated. Then CST, viscosity, SV, moisture content, COD, Zeta electric potential and morphological feature were tested. It is shown that the lowest CST of reclaimed water plant is 4.2s while the heating rate is 10℃/min and heating temperature is 80℃. SV, viscosity, moisture content of waste water plant sludge decrease and COD increases when heating temperature is higher. It is indicated that morphology of sludge changes under different heating conditions from fractal dimension and particle size data which is analyzed from image and calculated from cumulative weight percentage undersize of sludge particle. After 60~80℃ microwave pretreatment, dewater ability is proved.

Abstract:The hydrolysis and acidification abilities, dewaterabilities and sludge reduction of waste activated sludge (WAS) under four types of alkaline conditions, which were KOH, NaOH, Ca(OH)2 and Na2CO3, were investigated. Temperature and pH value were controlled at 35 ℃ and 10 respectively for all alkaline conditions investigated. WAS demonstrated different hydrolysis abilities, acidification abilities and dewaterabilities under the four types of alkaline conditions. The order of WAS hydrolysis abilities, acidification abilities, ammonia and phosphorus release, dewaterabilities under the four types of alkaline conditions were Na2CO3 > NaOH ≈ KOH > Ca(OH)2,, NaOH > KOH ≈ Na2CO3 > Ca(OH)2, Na2CO3 > NaOH ≈ KOH > Ca(OH)2 and Ca(OH)2,>Na2CO3 > NaOH ≈ KOH, respectively. Volatile suspended solid (VSS) reduction of WAS was the best under Na2CO3 condition; while under NaOH condition total suspended solid (TSS) reduction was the best.

Abstract:The physical model was simple in current outdoor thermal environment research, thus a new analysis method based on image processing was presented. With the combination of image processing and mathematical model, the new method was used to analyze the outdoor thermal environment of residential area and was validated by the comparison between the data from experiment and simulation. The results provide a new method for the simulation of outdoor thermal environment.

Abstract:An ELECTRE performance evaluation model was developed to outrank the different operating conditions of air conditioning systems. Five evaluation criteria covers total energy consumption, thermal comfort PMV and PPD, indoor air quality indices such as CO2 concentration and TVOC concentration. The performance under seven different operating conditions was outranked on the TRNSYS (transient system) simulation platform. Three assignment alternatives of weight coefficients were selected to calculate the relevant credibility scores respectively. The results indicate that the proposed evaluation model can outrank the different operating conditions and select the optimum one, Moreover different weight assignments have little influence on the outranking scores. Further investigation should focus on the more evaluating criteria such as control performance and others in the comprehensive evaluation of operating conditions.