Abstract:The observed data of surface settlement and the statistical analysis data of ground loss ratio caused by EPB shield tunnel construction are collected. Combining with the monitoring data and stratigraphic information of the sixteen sections in the interval from tunnel import to Shumuling station of the Chang-Zhu-Tan intercity high-speed rail Ⅱ standard, the ground loss and its factors induced by EPB shield tunnel construction are analyzed. The results show that the cumulative probability of ground loss ratio caused by EPB shield tunnel construction better obeys lognormal distribution; with the buried depth and the depth to diameter ratio increasing, the ground loss ratio decreases and tends to be stable, and the relationship between the ground loss ratio and the tunnel buried depth & the depth to diameter ratio can be approximately expressed by power functions; when H greater than 20m or H/D greater than 3.25, the ground loss ratio is basically stable near 0.75%, and the corresponding stratigraphic information indicates that the overlying strata in the shield tunnel is in the arch effect when constructing. So, it shows that the arch effect of the upper soil layer in the shield tunnel construction can be better control the ground loss ratio. With the increase of the time of shield tunneling through face, loss rate and nominal loss rate of the soil mass gradually increase and tend to be stable. It indicates that the consolidation deformation has great influence on the nominal ground loss ratio, and the maximum value is 4.58 times of the ground loss ratio caused by instantaneous settlement.

Abstract:Tou-xin-zao and ji-xin-zao are the two basic forms of tou-kung in Chinese ancient timber structures. To study the mechanical performance of the two types of tou-kung, finite element models are established for the typical tou-xin-zao and ji-xin-zao tou-kung in Raoyi Temple. The models are verified with previous experimental results and then subjected to vertical loading and horizontal low frequency cyclic loading, respectively. The finite element analysis shows that under vertical loading, the ji-xin-zao tou-kung experiences a strength hardening stage, with the ultimate bearing capacity 29.9% higher than that of tou-xin-zao tou-kung. It was found that the additional structural members (heng-gong) in ji-xin-zao tou-kung contributed to the higher bearing capacity. Under horizontal cyclic loading, the two tou-kung types behave equally well in terms of energy dissipation performance and both exhibite relatively plump hysteresis loops.

Abstract:Three specimens of frame supported shear wall with CFRP bars in transfer beam were tested under low cyclic loading, comparing to one with steel bars. And the failure modes, stress characteristics and hysteretic characteristics were analyzed. The nonlinear beam column elements based on stiffness method and zero length rotational spring element were selected through the OpenSees analysis platform. A numerical analysis model was established to analyze the frame supported shear wall, reasonably considerating bond slip of longitudinal reinforcement, and the simulation results were compared with the experimental. The results showed that the numerical model considering the bond slip of longitudinal reinforcement, can well simulate pinch characteristics of hysteresis curve of frame supported shear wall under cyclic loads. Besides, the yield load and ultimate load also had preferable simulation accuracy.

Abstract:In order to study the influences of the rotational restraint at pile head and the slight initial inclination of pile shaft on lateral pile responses under simultaneous vertical and lateral loads, semi-analytical solutions were put forward by matrix calculation, based on the coefficient of subgrade reaction expressed in the three-parameter form. The results were validated by the comparison with model test results and the existing solutions. The results indicated that when the coefficient of rotational restraint at pile head increases, the displacement at pile head and the maximum bending moment under ground decrease, while the bending moment at pile head and the distance between the maximum bending moment under ground and pile head increased. Both the maximum displacement and bending moment increased linearly with the increase of the initial inclination angle of pile shaft, and their changing rates increased when the vertical load increased. When the vertical load increased, the maximum displacement and bending moment increased, and their changing rates increased with increases of the vertical load and the initial inclination angle of pile shaft. The distance between the maximum bending moment under ground and ground decreased linearly when the vertical load increases.

Abstract:Self-made single blade screw anchor pile which was embedded soil pressure gauges was tested by uplift loading experiment. The variation of mounting torques, anchor's displacements and soil pressures on blade surface versus uplift loading under different embedded depths was recorded to analyse the relationship between installation torque, ultimate uplift bearing capacity and embedded depth ratios, and a preliminary inquiry was also made on the distribution regulation of soil pressure on helical blade surface. The results showed that, both of mounting torque and ultimate bearing capacity increased linearly with the buried depth ratio, and they were linearly independent to each other for the common influenced factors. In the pullout process, the increment of soil pressure on the surface of blade increased gradually from root to the edge, and the increment on the lower surface was far less than that of the upper one. The most of the area maintained the pressure constant except enlarged on few marginal area. The resultant force of two sides of blade increased with the loading, and the frictional resistance between pile and soil was parabolic developed. When the uplift displacement reacheed the limit ones of soil failure, the frictional resistance reached the peak value, and then decreased to zero. The bearing capacity of screw anchor pile could be calculated by the analysis of soil pressure on the blade surface.

Abstract:In the process of loading and deformation, the mechanics charactevistics of structured soils will be changed from natural state to damage state (remolded state) with the damage of structure; the damage variable and its evaluation equation are core to reflect the change. The variable expression is given for structured soils damage from the basic idea that damage is a course of energy dissipation. From the different mechanism of energy dissipation aroused by volumetric strain and shear strain, a basic expression that suits to general strain condition is put forward based on principle of superposition of compatible probability event. Through the analysis of the triaxial compression test, the damage evaluation equation to structured soils is set up, and it is revealed that the damage aroused by volumetric strain and shear strain abides by different evaluation law. Numerical calculation result can reflect the text perfectly, and it indicates that the method can reflect the stress-strain relation of structured soils perfectly.

Abstract:According to the fact that the sandy rock mass exposed to the natural environment is susceptible to water and soluble chemical attack, the triaxial shear test is carried out on sandstone specimens treated with CaCl₂ reagent with different pH value. The second-order simplified generalized Kelvin rheological model conforming to the experimental rule is chosen to deform it into three stress states according to the hypothesis of the Poisson's ratio. Based on the least squares method (LSMPS) of the search pattern, the optimal solution of the model parameters is obtained, and the sensitivity of the model to the change of the parameters is evaluated by the root mean square error. The delay time is used to evaluate the time required for the sandstone to stabilize the creep process in different chemical environments. The model parameters identified by the search pattern can make the calculated value of the model close to the measured value obtained by the loading test, which indicates that the model and its parameter identification method are suitable for determining the rheological characteristics of the sandstone under the disturbance of chemical factors.

Abstract:The monitoring components were put into the Shanghai-Nanjing intercity railway CFG pile-net composite foundation and Beijing-Shanghai high speed railway sand pile-net composite foundation of Kunshan test section, such as the soil pressure boxes, the settlement gauges and the pore water pressure gauges, etc., to monitor and obtain a large number of ground settlements(post construction), pile tops pressure and soil pressures, pore water pressures and other field test data in order to get variation law of properties of composite foundations. Working behavior of foundation during construction period and post construction settlement control effect were comparatively analyzed between the two different pile types (CFG pile-net and sand pile-net). The results showed that both CFG pile-net and sand pile-net preloading can meet the ballastless track of high-speed railway post construction settlement (less than 15 mm) control requirement according to the field tests. The total settlements and the velocity of settlement of CFG pile-net foundation were smaller than that of sand pile-net foundation, and its convergence speed was faster, which meant the latter requires a longer period of time to load. Affected by the pile stiffness, there was a big difference on the law of stress of pile and soil. The stress ratio of pile and soil in CFG pile-net foundation was increased with the increase of the filling of the embankment, and eventually stabilized, while that of sand pile-net foundation decreases with the increasing of load first, and then increase, presenting the wave shape change. And the CFG pile-net foundation excess pore water pressure dissipation rate was far less than the latter. In the case of short construction period, compared with the composite foundation of sand pile-net, the settlement control effect of CFG pile-net composite foundation treatment technology was more excellent.

Abstract:In order to optimize the processing scheme of medium compression soil foundation, the short pile-net composite foundation deformation characteristics is explored using the method of field test and theoretical analysis on a test section of Ganlong high-speed railway, and it's compared with the natural foundation. It is shown that the settlement of composite foundation reinforced area is 62%~75% of total settlement, the lateral displacement mainly occurred in preloading soil loading period and 20m depth is the main layer. Under similar conditions, the main stage of settlement, the main settlement layer thickness and settlement of cross section are quite different between composite foundation and natural foundation. The results show that the short pile-net composite foundation can effectively control the deformation of the medium compression soil foundation, which can provide reference for similar projects.

Abstract:Reinforced concrete structures generally work with cracks. Base on the studies at home and abroad, a crack influence coefficient about concrete carbonation γ_c, is defined. Mortar and concrete specimens with prefabricated cracks have been made for carbonation test. And the effect of water cement ratio, carbonation time, environment relative humidity, crack width, crack depth on γ_c is analyzed. A calculation model about carbonation depth in concrete cracks is obtained. Actual projects have been implemented to validate the model. It is shown that the model is applicable when the width of cracks in the range of 0.06~0.7 mm, and the bridge operation time have no significant effect on γ_c.

Abstract:Based on an important project at Qingdao, vertical static load test and the pile shaft stress test were conducted on five manual hole digging and pilling piles installed into argillaceous siltstone. The load transfer mechanism and vertical load bearing capacity of the large-diameter rock-socketed piles were discussed through the measured data. The test results showed that the load-displacement of five test piles was slow type, with the pile sedimentation less than 11 mm and larger unloading resilience ranging from 51%~75%, and all the piles had high bearing capacity which could meet the design requirements. Under the ultimate load, the proportion of head load transmitted and supported by the shaft base was between 10%~20% and decreased along with the increase of the shaft length and socked length (socketed into medium weather part), which showed the characteristic of end-support friction pile. The load of the shaft gradually worked from the top to the toe, and the soil side friction reached its ultimate value at first, while the peak side friction located at the medium of the socked length. The deeper of the socked length, the more safety stock of the pile, and the measured side friction was 2.5 times of the recommendation at the medium weathering rock. The percentage of the socked part supporting the total loading increased from 39% to 45% along with the increasing applied load, and the side friction of the socked part played an important role while the end resistance possessed a quick growth ratio. Based on the standard and data of static load test, vertical bearing capacity of the manual hole digging pile was refreshed, and the pile size was optimized in order to save the materials and improve the effectiveness of the construction, leading to the great economic benefits.

Abstract:With the acceleration of China's urbanization drive, construction wastes are on the rise. The application of recycled coarse aggregate could reduce the increasing construction wastes and save abundant sand resources. In order to sort and optimize the quality of recycled coarse aggregate, the quality evaluation model of recycled coarse aggregate is established based on the information entropy theory. The evaluation index system and single-index measurement functions are determined on the basis of Recycled Coarse Aggregate for Concrete. The weights of these indices are obtained from the information entropy theory. The evaluation matrix of single-index measurement and multiple-index evaluation vector are calculated according to the field data. The quality grade is assessed with credible recognition criteria. An analysis instance is shown, which verified the effectiveness of the proposed model. The result shows that the information entropy and uncertainty measurement theory can be applied to quality evaluation of single sample and distinguish quality of the same grade.

Abstract:In order to evaluate the influence rules of early frost damage on the bearing property and durability of concrete structure in service period, early frost experiments considering different admixtures and different freezing times were carried out. The surface damage forms of different freezing times were compared. The influence rules of freezing times and mineral admixtures on compressive strength, splitting tensile strength, dynamic elastic modulus and permeability of early frost admixture concrete were studied. The damage mechanism of early frost on service performance was discussed. The results showed that the damage degree of freezing time on compressive strength, splitting tensile strength and dynamic elastic modulus embodied as 2 h > 0.5 h ≈ 8 h > 1 d > 3 d. The most obvious loss was the splitting tensile strength, and the next was the dynamic elastic modulus. The least loss was the compressive strength. When 20% fly ash or 15% slag or 20% coal gangue was incorporated into concrete, the strength loss and the dynamic elastic modulus loss was the smallest and smaller than that of common concrete. With the increase of admixture, the anti-water-permeability and anti-air-penetration of concrete specimen at same freezing time were worsen. The anti-permeability of unfrozen concrete was the best, and the next is 3-day frozen concrete. The third is 1-day frozen concrete, and the anti-permeability of 0.5-hour frozen and 2-hour frozen and 8-hour frozen concrete were the worst and even beyond the test range of AutoClam equipment.

Abstract:The three-dimensional random aggregate concrete model is usually considered as a three-phase composite materials which are composed of aggregates, cement matrix and the interface layers. A hybrid realization method is proposed in order to rapidly obtain the concrete aggregate models with high volume fraction of spherical particles by combining Fortran and ANSYS software. The corresponding ellipsoid aggregate (pebble) model, the convex polyhedral aggregate (gravel) model and the mixed model with different shape aggregates are also generated. The results of several examples show that the relevant data of three-graded concrete model with spherical aggregate particles can be obtained rapidly and the corresponding aggregate content can reach about 65%. The hybrid realization method can easily separate the aggregate particles from the interface layers and thus the complex element attribute discrimination can be avoided in the finite element mesh. Finally, the validity of the proposed hybrid method is further verified by finite element numerical simulation for the ellipsoidal aggregate model and the convex polyhedral aggregate model.

Abstract:Insulation is one of the most effective measures in energy-saving renovation of existing buildings. The determination of type and thickness for the insulation material is crucial in the energy-saving design of wall, which is determined by multiple target parameters. An optimization model combined the numerical method with multi-objective genetic algorithm (NSGA-Ⅱ) is established based on the inverse problem research method. The total energy consumption of the unit area wall and the transformation cost are selected as the objective parameters, and the synergic design for type and thickness of the insulation material is made for the existing building wall renovation in Chengdu. The results show that there are 6 of the 8 kinds of insulation materials are not the optimal solutions with the conventional thickness. However, the solutions can approach the Pareto frontier by changing the thickness or unit price of the insulation materials, and a balance can be realized between the minimum annual energy consumption and reconstruction cost. The method proposed offers a new idea for building energy-saving design. The conclusions can provide references for the similar energy-saving renovation in Chengdu.

Abstract:Flocculation is one of the most important water pollution control methods. Flocculant is a key foundation of flocculation pollution control method, which plays a vital role in the final water treatment effect. Among these, cationic polyacrylamide is an important type of water treatment agent, which has been of concern in the field of water treatment. The initiation system in the free radical copolymerization and research progress of cationic polyacrylamide are summarized. Characteristics and application of initiation system in the polymerization, such as azo-initiator system, redox initiation system, complex initiation system and UV initiation system are introduced mainly. The types and application of common cationic monomers in the copolymerization are elaborated. Furthermore, its future development tendency and research direction are predicted.

Abstract:Large amounts of sewage with nitrogen, phosphorus, potassium and other nutrients into the river lake will cause the algae bloom. Algae-lysing bacteria which can effectively degrade cyanobacteria in water is a potential treatment. An algicidal bacterium against toxic Microcystis aeruginosastrain G6 is isolated from reed roots in Baidu port of Taihu Lake. According to phylogenetic analysis, strain G6(Bacillus sp) is identified as Bacillus sp.The strain G6 which cultivated to the logarithmic phase is voted to water with bacteria and algae ratio of 1:10. The Chl-a of algae fluid could be reduced up to 82% when it is placed in the light incubator of 28℃ temperature, light intensity 2 500 lux, and photoperiod 12 h:12 h for 7 days. Strain G6 has the character that it can kill the algae cells without light. It is conducive to bacteria breeding and degradate algae in the deep sea which lack of light. The strain G6 could produce substance which can dissolv algae to kill microcystis aeruginosa, which is an indirect way to kill algae. The substance has thermal stability to kill the algae cells at high temperature.

Abstract:The micro aerobic and anaerobic hydrolysis acidification were used to improve the quality of gelatin wastewater. The effects of hydraulic retention time were explored. The experimental results showed that when the hydraulic retention time was 72 h, the COD removal rate of micro aerobic reactor could reach up to 25% when dissolved oxygen was 1.3~1.6 mg/L, and that of anaerobic reactor up to 22% when dissolved oxygen was 0.3~0.5 mg/L. The content of VFA of micro aerobic reactor was 12 mg/L, and that of the anaerobic reactor was lower to 8 mg/L. The pH of aerobic reactor was reduced to 7.5 from original 12.5, and that of the anaerobic reactor was reduced to 8.0. The removal rate of protein for both reactors was more than 90%. However, the ammonia nitrogen of micro aerobic reactor was only 22 mg/L, less than that of the anaerobic reactor, which indicated that anaerobic conditions was beneficial for spread and volatile of ammonia nitrogen. All the data suggested that hydrolytic acidification of micro aerobic reactor was better than anaerobic reactor for the pretreatment of gelatin wastewater.

Abstract:Urban water supply is a nonlinear and non-stationary time series, and the combination forecasting model can get more accurate results. Through in-depth analysis of chaotic local-region method and neural network prediction model, this paper puts forward a new combination forecasting model, which uses chaotic local-region method to make a preliminary forecast for urban daily water supply, and then the prediction result is updated by neural network. The proposed combined model makes use of complementary advantages of the chaotic local-region method and the neural network, improving synchronously the accuracy and computational efficiency of the prediction results. To verify the proposed model, the prediction accuracy of the four single prediction models of Chaotic local-region method,BPNN, RBF and GRNN neural network and three corresponding combined models are analyzed quantitatively using seven years water supply data. The results show that combination forecasting model is of higher accuracy than single prediction model, and chaotic local-region method plus GRNN neural network combination model has highest accuracy with much lower computation time than single neural network predication model.

Abstract:In this paper, γ-Al2O3 was used as the carrier to screen the active ingredients. As the result, Ti and Sn were used to prepared the supported γ-Al2O3 Particle. IR, XRD, SEM, and XRD were used to characterize the particle electrode. The effect of electrolysis time on the three-dimensional particle electrode electro-catalytic oxidation of chloramphenicol was studied The chloramphenicol removal rate and TOC removal rate were 72.8% and 4.2% obtained at 100 mg/L chloramphenicol and 180 min, respectively. The degradation process of chloramphenicol was approximate first-order kinetics equation, and the initial concentration had less effect on the removal. ·OH played a key role in particle electrodes electro-catalytic oxidation process of chloramphenicol. Adding t-butanol to clean ·OH, the removal of chloramphenicol was reduced to about 30% under the same conditions. This indicated that the degradation of the chloramphenicol was coordinated effect of directed oxidation of anode and indirected oxidation of ·OH.