Applied Mechanics and Materials Vols. 477-478

Abstract: A two-dimensional numerical model was built for the typical shallow reservoir with serious thermal pollution in the North China Plain. After calibration and validation, four scenarios were developed to study the impacts of water transfer on thermal structure. Model results showed that the hydrodynamic and water temperature could be well simulated. The effects of water transfer on thermal structure showed in decreasing temperature rises, which was more remarkable for regions far away from the releasing point of thermal discharge. In terms of reducing temperature, 45.5 m³/s was the most efficient inflow rate among the four representative flow rates. This study provides useful information for reservoir sustainable management. Keywords: water transfer, temperature, numerical simulation, Douhe reservoir.

Abstract: Subjective factors could affect the weight distribution of each index in evaluation of reservoir eutrophication, so the example used entropy to deal with the weight distribution of each index. Combined attributes recognition method, the writer selected six indicators to build the entropy weight of attribute recognition model about reservoir eutrophication of ten large reservoirs in Guangdong Province. By comparing the calculated results with the results of matter-element model, the calculation results were basically consistent. So entropy weight of attribute recognition model is applicable to the evaluation of the reservoir eutrophication and it can ensure the fairness and reasonableness of weight distribution.

Abstract: In view of the definition on the slope of the specification, the classification of water conservancy engineering slope is obtained. Through the analysis of the unique features of different types of slope of specific projects, the focus of different slope is pointed out. After the risk analysis and evaluation on the slope, according to the characteristics of the water conservancy engineering slope, it is proposed that engineering measures and non-engineering measures can be adopted to transfer or reduce the risk.

Abstract: Groundwater plays an important role and accounts for two-thirds of the total water supply in Beijing plain. Overexploitation of groundwater has caused continuous decline in groundwater levels, land subsidence and other environmental and ecological problems. To analyze current status and predict future trends in groundwater resources, a 3D transient groundwater flow model was established and used to simulate various groundwater resources development schemes. With considering some facters such as groundwater exploitation, river outflow, groundwater levels and so on, an evaluation index system was constructed. Based on this index system a multi-object decision model was established for estimation of groundwater development schemes and proven to be very useful for scientific analysis of reasonable development and utilization of groundwater resources.

Abstract: Numerical model of thermo-hydro-mechanical coupling processes of radioactive waste during the long-time disposal is established with the multi-fields coupling theory, based on the theory of continuum mechanics, thermo elastic material mechanics, and considered the influence of the variation of water viscosity due to temperature variation on permeability of pore water. The whole process of excavation,heating phase and cooling phase have been simulated in the calculation;and the calculated results are analyzed. It indicates that the anisotropy of thermo-hydro-mechanical behavior of the argillite rock is the main factor affecting temperature distribution,pore pressure and stress fields.The results make clear that the differences of coupling action and uncoupling action are obvious and the effects of coupling cannot be ignored.

Abstract: This research mainly focuses on the analysis of factors influences on gravity dam open crack on the basis of theoretical regression equations. It calculated the equations with multiple stepwise regression and selected factors that had significant influence on gravity dam crack to form the model equations. Moreover, it evaluated the reliability and accuracy of model equation through statistical parameters and chart to get a reasonable analysis.

Abstract: Based on the research of various kinds of composite polymers of redispersible latex powder, cellulose ether, organic silicon water repellent and so on , with additions of polymers and the additive of mineral powder-silica fume composite minerals, the paper studies on the influence of composite polymer mainly made of materials on concrete mechanical performance and microstructure. With the addition of composite polymers, despite that the early hydration reaction is delayed, the hydration reaction of 28d speeds up evidently and its internal structure becomes tighter, which is beneficial for the improvement of concrete persistence.

Abstract: Foamed asphalt cold-regenerating technique is used to study the overhaul engineering of Binshi Expressway in 2012 (Tianjin Section) to analyze influences of different milling parameters upon the grading difference of materials of recovered asphalt pavement (RAP); and vibration compaction is used to confirm the maximum dry density and the optimum water content of regenerating mixture in the design of mix proportion to provide more reliable control parameters for site construction. Furthermore, site construction technology of cold-regeneration technique is expounded and analyzed and key control points of all links are summarized to offer technical reference for promotion and application of foamed asphalt cold-regenerating technique in Tianjin.

Abstract: The compatibility of low sulfate cement with naphthalene (NS) and polycarboxylate (PCE) type superplasticizers was discussed. The flowability of slurry and the adsorption of superplasticizers (SP) were investigated by mini slump test and TOC. The results show that severe compatibility degeneration is caused by low sulfate content in cement slurry. The water demand of slurry, the standard dosage and adsorbed amount of SPs were dramatically raised. In the cement slurry with low sulfate content, polycarboxylate type superplasticizers presents better performance than naphthalene type. The PCE with lower charge density presents better robustness. It is recommended in the preparation of concrete to avoid the incompatibility problems caused by lack of sulfate in cement paste.

Abstract: Hydrating and calcining method combined with the kinetic equation were adopted to describe the hydration kinetics process of the laboratory-calcined CaO expansion clinker, XRD and SEM were used to test and analysis its mineral compo-sition and microstructure as well. The results show that, hydration reaction process in pure water of f-CaO contained in the CaO expansion clinker meets the Avrami isothermal crystallization kinetics model, and the hydration degree increases with temperature, with the relation between reaction rate constant and temperature conforming to Arrhenius law; the CaO expansion clinker powder contains a large number of particles in which f-CaO, CaSO₄, Ca₄Al₆O₁₂SO₄ (partly still containing calcium silicates) phases existing at the same time, by the impact of the presence of impurity phases and the difference of calcining conditions, the hydration activity of f-CaO contained in CaO expansion clinker was different from that of pure CaO and that of f-CaO wrapped in cement clinker or high-calcium fly ash.