Abstract:

Abstract:Triaxial compression rheological experiments on carbonaceous slate specimens of deep buried tunnel were carried out on the rock rheology testing machine. Along with the increase of loading stress level and the improvement of moisture conditions, the initial attenuation creep phase, the stabilization creep phase, and the speedup creep phase were produced. By connecting Burgers model and the nonlinear viscoplastic body consisted of nonlinear viscous component η(n,t) parallel connected with the plastic component in series, the improved model could describe the speedup creep phase. Using this model to fit and analyze the rheological parameters of different moisture conditions, it is shown that η〖KG0.005mm〗 M、E M、E K and η〖KG0.005mm〗 Kwill decrease with negative exponential trend. Then water damage D(w) was introduced, and through deriving damage evolution equation, the nonlinear viscoelasticplastic model with water damage effect was established. Finally, the time effect deformation of surrounding rock under different times and different moisture conditions was studied by numerical simulation, and the results show that primary support should close in 168 h, and the best construction time for secondary lining is 360 h after the primary support is closed.

Abstract:Deep excavation in soft clay often brings soil stress disturbance and soil deformation, which would bring differential settlement and structural cracks. It probably brings safety problems to adjacent underground tunnels. Therefore, it is necessary to predict tunnel displacement induced by excavation for tunnel’s security. A new method was proposed to estimate the heave of underlying tunnel induced by adjacent excavation verified by field measurements. The soil deformation by excavated soil gravity was analyzed by application of Boussinesq solution. The soil deformation by tunnel surface pressure was analyzed by Mindlin solution. The tunnel was assumed to be an elastic beam on foundation to simulate the tunnel, in which interaction analysis of tunnel and soil was employed. In consideration of rheologic soil， Viscoelastic model was employed to analyze soil nonlinear displacement with time in soft clay. Tunnel displacements were discussed by different excavation cases. A case study showed a good agreement between the results from the prediction and the measurement.

Abstract:In order to investigate the dynamic behavior of geogrid reinforced pile supported embankments (GRPS) under moving load, a three dimensional coupled mechanical and hydraulic model was built by FLAC 3D. The results from two cases including unreinforced and no pile embankments, and geogrid reinforced pile supported embankments were presented. The behaviors of vertical displacement, pile soil stress ratio, excess pore water pressure, and vertical acceleration under two cases were compared and discussed. Additionally, studies on the effect of speed and weight of the moving load were performed. It is indicated that the value of vertical displacement, pile soil stress ratio, excess pore water pressure, and vertical acceleration of GRPS decrease evidently compared with those of unreinforced and no pile embankment, which is caused by the soil arching effect and the reinforcement effect. It is also shown that the greater the axle load value is, the less the beneficial effect of GRPS on the vertical displacement. With the increase of the moving speed of the load, the vertical displacement increases.

Abstract:The urban tunnel construction will cause ground movement and the deformation or even damage of the nearby pipelines. It's very common in practice that the structural stiffness is ignored in the settlement prediction and damage assessment because of the complexity of tunnel soil pipeline interaction. Based on the study of pipeline settlement profiles measured from several tunnelling projects, an observation is put forward that the settlement profiles of the pipeline can be fit very well by the Gaussian equation in case of using a larger trough width parameter K influenced by the stiffness of the pipeline. Thus an empirical relationship between the parameter K and the stiffness of the pipeline was proposed which can be used to predict the trough parameter according to the stiffness, and a ‘Modified Stiffness Method' was proposed.

Abstract:In order to investigate the 1D (one dimensional) compression behavior for China structured clays in a simple way, the experimental results on intact and reconstituted clay samples for 12 typical China natural clays located from south to north in China were analyzed. Based on these, a modeling method for destructuration behavior was proposed by introducing the bonding ratio and furthermore extended to disturbance soil model by using disturbance state concept. The proposed model was then validated by simulating 1D compression tests of various natural clays.

Abstract:The rheological characteristics of clay soils were described by Merchant mode. The governing equation for consolidation of layered clay soils exhibiting rheological characteristics was solved using the finite element method. Matrix formulation was derived by Galerkin's weighting residual method. The proposed FE procedure was encoded in a program. The presented formulation and program code were examined by using the analytical results of two simplified problems, a one layer clay soil exhibiting rheological characteristics and a double layer elastic clay soil. The comparison shows that the numerical results agree well with those of analytical results. A three layer clay soil exhibiting rheological characteristics was used to analyze influence of rheological characteristics and its parameter η 1 on different layers at different time. The results show that consolidation of clay exhibiting rheological characteristics is slower than that of clay exhibiting elastic characteristics. The phenomenon becomes more obvious over time and the distance between the clay and the pervious plane increases. Difference between the pore pressure dissipation of rheological clay and that of elastic clay reaches its climax when the consolidation degree of clay is in the range from 80% to 90%. Difference between the consolidation degree of rheological clay and that of elastic clay becomes larger and the influence time is earlier with higher creep parameter η 1.

Abstract:To know well the impact on the deformation of underground diaphragm wall caused by soil excavation, centrifugal model tests reflecting Shanghai soft soil creep effects were designed, and finite element was used to calculate the deformation of underground diaphragm wall caused by different excavation timeline, sequence and width based on the top down construction method in the deep and large foundation pit of Shanghai Expo axis underground complex project. Centrifuge model tests and monitoring data indicate that the results of numerical calculation are approximately close to the horizontal displacement of the underground diaphragm wall measured in site, which reflects the deformation behavior of excavation. The results show that remained berm and middle plate have good control over the deformation of underground diaphragm wall. Most part of underground diaphragm wall deformation caused by soil creep occurs after the remained berm is excavated. So in order to decrease the deformation of underground diaphragm wall, it would be useful to conduct plate structures as soon as the remained berm is excavated. The excavation width of remained berm in the north part is less than that in the south part. It will be advisable to finally excavate the remained berm where there are protected objects nearby.

Abstract:The interface interaction between geogrid and soil is one of the key issues on geosynthetic reinforced soil structures. Comparative analysis of properties of geogrid clay interface under the different normal stresses and water contents of clay were conducted by medium sized pullout tests. The results show that ultimate pullout force of geogrid, interfacial cohesion and frictional coefficient are significantly affected by water content of clay. Ultimate pullout force of geogrid tends to be remarkably different when subjecting to different normal stresses at a lower water content. And frictional coefficient of interface decreases with the increase of water content, and interfacial cohesion has a tendency to increase followed by decrease with the increase of water content. Moreover, aforementioned three parameters can keep constant when water content is close to value at plasticity limit. The curves of load and displacement possess three stages: linear increase, non linear increase and ultimate pullout. As water content increases, the interval nonlinear changing stage is not conspicuous. Furthermore, it is found that geogrid strains in transversal ribs tend to increase but to reduce in longitudinal ribs when last level load is kept for given hours and then followed by unloading pullout force.

Abstract:Anchorage zone on tower of cable stayed bridge has complex structures and stress distributions, and keeping it on a safety state under a large tonnage tension and prestress is more concerned in design and construction. The stress distribution of the anchorage zone was analyzed by 3D finite element method. Furthermore, the mechanical properties and the rules of stress distributions were investigated and compared in three different load cases. The results show that the disposition form of level prestressing tendon is reasonable. The stress of the entire tendon is very close to 1 116 MPa under the tension control stress of 1 260 MPa. It is shown that the intensity of the tendon has given full play to prestress and it is not appropriate to increase the tension control stress.

Abstract:In order to simplify the analyses of thin walled open profile bars, a thin walled bar was split into two parts which were dominated by in plane and out plane loading effects respectively. The in plane loading effects were focused. On the basis of appropriate simplified stress and strain conditions, each plate was analyzed and the results were integrated into vectors, resulting in the slabs' in plane tension bending resistance system of thin walled open profile bars, which reflects their axial stretch/compression, bending and warping properties. And then the deformation equation and the stiffness equation were set up. Because longitudinal interaction forces between plates were introduced in the definition of the plates' in plane bending moments, the deduction and conclusions here were consistent in form with those in bending theory. Principal axes' directions, shear center's coordinates, principal inertia moments and sectorial inertia moment of thin walled open sections can be deduced by the slabs disassembled method proposed here. Lateral deformed bars' analysis based on those sectional parameters in classical theory is proved to be inefficient, where additional “rigid contour hypothesis” has to be introduced.

Abstract:In the current unified standard for reliability design, it lacks full considerations of the range of load effect ratio for reliability analysis of light weight steel structures. Firstly, a computational method based on stress was proposed to calculate load effect ratio, which solves the problem that which kind of load effects can be chosen to calculate load effect ratio when the member fails with actions of several kinds of internal forces. Then, the range of load effect ratio was studied for light weight steel structures after some analyses of several members with this method. It is found that the load effect ratio of light weight steel structures can adopt large values under the disadvantage distributions of snow load. The reliability was also calculated for light weight steel structures designed with current partial factors. Its result shows that the reliability of light weight steel structure is low. Finally, the reliability was analyzed for light weight steel structures with different load effect ratios when snow load exceeded the design standard level. It indicates that the reliability is low for light weight steel structures with large load effect ratio. This provides some complementary explanations for the phenomena that the light steel structures are more likely to fail under snow disaster.

Abstract:Equivalent linear system method is the main method of nonlinear structural system random response analysis. While it would generate big error when the results of equivalent linear system method are used to analyze the structural dynamic reliability. Through minimum mean square error principle, general nonlinear system was converted to equivalent Duffing nonlinear system, based on which the structural dynamic reliability was analyzed. The accurate steady state analytic solution of Duffing nonlinear system can be worked out by FPK equation, so it is not only convenient but also accurate to analyze structural dynamic reliability by using the equivalent nonlinear system method. It is also shown that the analysis results of equivalent nonlinear system method presented here is reliable and the calculation accuracy is higher than equivalent linear system method apparently through the example analysis.

Abstract:Based on Petri net theory and workflow model, a 9 tuple colored Petri net simulation model of earthmoving operations was presented focusing on the equipment management in the earthmoving construction. The dynamic changes of workflow and information flow in the construction process were illustrated in the model, and the constraint relationship between equipment and construction conditions was taken into account. Based on the information of the number of equipment and cost, the simulation for the construction situation, estimated completion time, cost, and equipment productivity were conducted. The model was operated based on the CPN Tools platform. And sensitivity analysis and model validation on the model were carried out by simulating the data collected in a real case, which demonstrates that the model can improve the accuracy of the simulation results in the earthmoving operation construction process.

Abstract:The behavior of plate in compression plays a basic role in relevant research. There are significant differences between stainless steel and carbon steel plates in structural behavior. Analysis on the behavior of stainless steel plate in compression was presented. The development of FE models for analyzing stainless steel plates in compression was described based on the results of Rasmussen's test. And the strength curve was achieved by such advanced FE models with a high degree of accuracy. The explicit strength equations and design method were proposed for determining the local buckling strength of stainless plate and cold formed rectangular hollow section in compression. It is shown that the numerical simulation results achieved by using Quach model are accurate.

Abstract:Based on the sense of Liapunov dynamic stability and the features of elastic buckling of arch bridge, and using the static buckling eigenvalue as well as linear time history analysis result, a simplified method for evaluating the elastic dynamic instability was developed from the so called “dynamic eigenvalue method” that needs to extract the minimum buckling eigenvalues step by step under the whole earthquake excitation. The presented method was compared and validated to be efficient and accurate via a case study, and therefore it could be used as a more effective method to study the dynamic stability issue of long span arch bridges and other civil engineering structures.

Abstract:Quasi static test results of 71 rectangular hollow bridge piers were collected to study the deformation capacity and amount of confining reinforcement in the potential plastic hinge region of the bridge piers. The deformation capacity of the hollow bridge piers with different failure modes were analyzed, and current codes provisions for the amount of confining reinforcement in hollow bridge piers were evaluated. Then, main factors influencing the deformation capacity of the piers were discussed based on multiple linear regression analysis and correlation analysis. At last, design equations based on Caltrans code of required confining reinforcement for rectangular hollow bridge piers were proposed. It is found that both the Caltrans and ACI codes show great reliability for the flexural failure mode and deformation capacity of the hollow bridge piers while the Chinese JTG/T B02-01-2008 code is unsafe. Also, the deformation capacity of the hollow bridge piers increases with the increase of the transverse reinforcement, longitudinal reinforcement, and web width, and decreases with the increase of the axial load ratio.

Abstract:Energy consumption of water intake is one of the key factors for energy saving in the application of the open loop surface water heat pump system. An energy efficiency ratio coupling model for open loop surface water source heat pump systems was established on the basis of the energy consumption model for the water intake and the heat pump units. According to energy saving rate and regulation of energy consumption of water intake, dynamic temperature limits of water intake in different water supply temperature of cooling tower and different pump head were proposed so as to find a calculation method of temperature limits of water intake of open loop surface water heat pumps. Moreover, the energy saving rate of surface water source heat pump systems compared with traditional air conditioning systems under various condition was also calculated.

Abstract:A mathematical model of solar energy storage ventilation system was built in order to calculate the heat storage during daytime and the ventilation rate during nighttime. Based on meteorological parameters of Kunming in China, phase change materials(PCM) were used at the temperature of 38 ℃, 44 ℃, 50 ℃ and 63 ℃ respectively to search the relationship between ventilation volume and the angle of chimney. The modeling calculation results show that for different phase change materials, and in any angle, the trend of heat accumulation is consistent, namely heat accumulation is smaller with a higher phase change temperature. Considering both the average hourly ventilation volume and the duration, the best angle of this system should be 45°, and the best phase change material should be 38 ℃ myristoyl.

Abstract:Installing small wind turbines on the roof of buildings is a new way of wind power utilization in recently years. Based on the annual mean wind speed, the efficiency of wind power utilization on roofs of buildings was studied and the evaluation indexes for the utilization efficiency were proposed. With the help of CFD numerical analysis, the analysis on wind power utilization efficiency on flat roofs of rectangular buildings was carried out. The performance indexes of reference points under different windward angles were investigated. The best position and arrangement of wind turbines on the roof were also discussed. Furthermore, the utilization efficiency of four roofs with different shapes were analyzed and compared with that of flat roof.

Abstract:Through comparison of internal surface temperature (IST) of green roofs with that without green roofs through field measurement and statistics analysis, green roof under natural convention climate in summer was analyzed. Distribution frequency and sum of IST under the conditions with and without green roofs were investigated by dividing IST into several ranges. It is shown that the frequency of IST lower than 34 ℃ for green roofs was 90%, which was about 1.6 times of that for roofs without green. While the frequency of IST exceeding 34 ℃ for green roofs was 4.6% of that for roofs without green, and the sum of IST exceeding 30 ℃ was about 1/3 of that for roofs without greening. Moreover, the property of thermal insulation of green roofs had strong positive relation with outdoor temperature. The thermal insulation characteristic was better as outdoor temperature grew up.

Abstract:Based on the strong poly role of phosphate on polymeric ferric sulfate (PFS), with PFS and Na 2HPO 4 as raw materials, a new type of composite flocculant polymeric phosphate ferric sulfate (PPFS) was developed. The structure of PPFS was characterized by IR and SEM, and the mechanism of flocculation was analyzed. The factors affecting phthalic acid esters (PAEs) removal were discussed, including dosage, nPO 43-/nFe3+and alkalization degree. The results indicate that PPFS has good removal effect to PAEs. When the dosage is 70 mg·L-1, nPO 43-/nFe3+ is 0.3 and alkalization degree is 30%, the removal rate of dimethyl phthalate, diethyl phthalate, dibutyl phthalate and bis (2 ethylhexyl) phthalate are 67.93%,84.55%,90.88%,88.69%, respectively.

Abstract:Jar tests were used to study the removal efficiency and influence factors caused by common anions and organic compounds of bromide in water by a new magnetic ion exchange resin (MIEX). The results show that MIEX can remove bromide in pure water effectively. The removal rates of bromide by MIEX are all over 90% when the equilibrium time of ion exchange reaction between MIEX and bromide is 5 min and 3 min and the dosage is 10 mL/L and 20 mL/L, respectively. Even containing other common negatively charged matter which has inhibitory effect to some extent, the removal rates reach 50%. Anionic content and the selectivity of MIEX are the main influence factors to reduce bromide in water by MIEX. The existence of organic compounds decreases the removal rate of bromide in water by MIEX, which is approximately 70%. There are differences between anions and organic compounds in removal processes by MIEX. The equilibrium time of ion exchange reaction removing anions is about 5 min, while it takes over 20 min to remove organic compounds measured with UV 254 and DOC, respectively by MIEX with the dosage of 10 mL/L.

Abstract:In the experiment, the denitrifying phosphorus removing bacteria (DPB) was cultivated by high phosphorus and low carbon source influent. It was cultivated successfully by the 2 stage mode for about 100 d. The first stage was about 40 d, which was with the mode of anaerobic/aerobic to enrich the phosphorus accumulating organisms (PAOs). The maximum amounts of the phosphorus release, phosphorus uptake and phosphorus removal were 77.2 mg/L, 89.4 mg/L and 250 mg/L respectively. The second stage was 60 d, which was with the mode of anaerobic/anoxic/aerobic. In this stage, the ratio of denitrifying phosphorus uptake amount to the total phosphorus uptake amount had an ascending tendency. The cultivation of nitrifying activated sludge was about 100 d, with the 50 mg/L ammonia removal amount and more than 98.5% ammonia removal efficiency. Nitrification rate fitted zero order kinetic equation, and the specific nitrification rate constant was 0.002 4 h-1. Phosphorus uptake rates fitted first order absorption kinetic equation. The uptake rate constants under aerobic and anoxic conditions were 0.377 and 0.740 L/(g·h-1). The cultivated DPB sludge and nitrifying activated sludge were used in an anaerobic/anoxic/nitrification sequencing batch reactor（A 2N-SBR） process to remove nitrogen and phosphorus. When the concentrations of influent COD, ammonia and phosphorus were 188.0 mg/L, 54.8 mg/L and 725 mg/L, the removal efficiencies of COD, ammonia and phosphorus were 935%, 76.7% and 94.1% respectively.

Abstract:A phosphorus accumulation organism strain AP3 with Fe (Ⅲ) as electronic acceptor was screened from activated sludge through such processes as dilution plate method, poly P, PHB staining and ferric citrate reduction. Its 16S rDNA is identical to that of Pseudomonas mosseliisp ATCCBAA 99 at 99% level. By comparing the AP3 being cultured in ferric citrate fluid medium and the one in non ferric fluid medium at 27 ℃, it was found that ferric citrate fluid medium was beneficial for the AP3. AP3 cultured in non ferric fluid medium showed significant anaerobic and phosphorus releasing characteristic, the phosphorus releasing amount of which was 3.68 mg·L-1. AP3 cultured in ferric fluid medium was also characterized by anaerobic and phosphorus releasing property at the first stage, the phosphorus releasing amount of which was 662 mg·L-1，which was higher than the former; And at the second stage which started from the 10h, it was characterized by anaerobic and phosphorus accumulating property, the phosphorus accumulating amount of which was 5.89 mg·L-1. Fe (Ⅲ) is the electron acceptor of AP3 which shows typical anaerobic and phosphorus absorbing property.

Abstract:The mobility of heavy metals including Cd, Cr and As, among sediment, pore water and overlying water under different hydrodynamic conditions in 15 d was analyzed with hydrodynamic flumes. Three velocities were designed as 4.01 cm/s for slow flow in Flume A, 12.70 cm/s for middle flow in Flume B, and 20.23 cm/s for fast flow in Flume C. Results show that: 1) Increasing the velocities of flow can promote the release of heavy metals; 2) As of pore water presented higher concentration, which shows the mobile trends of As are from pore water to overlying water; 3) Sediments suspended are the main reason for the increase of concentration of heavy metals in the overlying water. Compared with the static condition, hydrodynamic conditions significantly affect the mobility of heavy metals. And the changing characters in each flume are different for each kind of metals in different kinds of medium (overlying water, pore water, and surface sediment). Moreover, the extent of hydrodynamic impacts on the mobility of heavy metals is overlying water>sediment>pore water.