Applied Mechanics and Materials Vols. 174-177

Abstract: The special viscoelastic gel has been successfully applied to deal with severe lost circulation problem in more than thirty wells. It was demonstrated that the viscoelastic gel exerted important functions in dealing with the underground blowout-loss circulation coexistence problem in Shuangmiao Well 1, and the high H₂S content blowout-loss circulation coexistence problem in Luojia Well 2, and high CO₂ content blowout-loss circulation coexistence problem in Xushen-8 well H1. One of the important reasons why the gel was applied to deal with the problems successfully was that the gel has strong anti-dilution ability. The strong anti-dilution ability of the gel is one of the important reasons why to plugging successfully. This paper studied the heat of solution of the polymer ZND and heat of dilution of the gel-ZND based on thermodynamics. The smaller the heat of dilution is, the stronger anti-dilution ability of the gel ZND has. Chose the volume change rate through screening out to characterize the anti-dilution property of the gel and investigated the affecting factors. The experimental results showed that the quantity of screen residue decreased with the increasing of temperature, shear rate and shear time，but increased with increasing of concentration. Studied anti-dilution ability of gel-ZND in the fragmentized zone simulated by a large size plugging device. The displaced volume rates of gel-ZND with concentration above 1.0% displaced by equivalent pore volume water are all smaller than 16%. The displaced volume rate of the gel was less than 2% continuing displaced by the gel-ZND by two times pore volume water when water breakthrough came. It validated that the special gel-ZND had strong anti-dilution ability. The results provide experimental basis and theoretical guidance for resolving the potential safety hazard caused by severe loss circulation or blowout-loss circulation coexistence.

Abstract: Based on the RCC（roller compacted concrete） gravity dam, considering the multiphase, heterogeneity and microscopic structure characteristics of RCC, we use the RFPA analysis system to analyze the whole destruction process of the RCC weak level under the action of the pure water pressure in this paper. By simulation, we obtained the distribution of the stress, elastic modulus, water pressure on the whole failure process of RCC weak level and several parameters, such as the up crack load, instability load and critical crack propagation length. By calculation, we got the double K fracture toughness of RCC under the different of water pressure, and the results show that the up crack toughness and instability toughness change regularly with the increasing of water pressure initial value in the mass.

Abstract: BiFeO₃ polyhedrons had been successfully synthesized via a hydrothermal method. The as-prepared products were characterized by power X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The possible mechanisms for the formation of BiFeO₃ polyhedrons were discussed. Though comparison experiments, it was found that the kind of precursor played a key role on the morphology control of BiFeO₃ crystals.

Abstract: A 74-mm-diameter split Hopkinson pressure bar (SHPB) is used to test the dynamic mechanical behavior of concrete and cement mortar. Experimental results show that concrete and cement mortar are rate-dependent. The load-carrying capacity of concrete is higher than that of cement mortar. Whereas, the maximum strain of concrete is lower than that of cement mortar. No matter for concrete or cement mortar, with the increase of impact velocity, the fragment size of specimens after experiment decreases.

Abstract: The BiFeO3 hollow crystals were successfully prepared at 200oC by a Al³⁺ assisted hydrothermal method. The structures and morphologies of the as-obtained products were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). A morphology evolution from irregular shape to square, hollow, and sphere-like was observed as the Al ions concentration varied from 0% to 1.5%. The possible growth mechanism of the BiFeO₃ hollow crystals was also discussed.

Abstract: This study is to report the synthesis of polyacrylate-siloxane latex with vinyl triethoxysilane(DB-151), methyl methacrylate(MMA) acrylic acid(AA), butyl acrylate(BA) by emulsion copolymerization and characterized by FTIR. The physical properties are also analysized by water absorption, pencil hardness, circle adhesion method, etc.. The polymerization factors for emulsion had been discussed in several aspects. The results showed that the optimal conditions for synthesizing silicone-acrylate emulsion were of DB -151content of 6%~8%, emulsifier OP-10/SDS/ DNS-458 ratio:2/1/1, in stirring rate 450 r/min in the period of disperse and emulsification, stirring rate 200 r/min in the period of synthesis, with reaction temperature 75°C.

Abstract: Interior water migrated towards the surface area when concrete suffered minus temperature during infant ages. Cover concrete became the worst part after the complicated process of water freezing – thawing, intermittent hydration of cementious materials and volatilization. Presentation quality, carbonization depth and rebound value in 120 d ages were observed and tested in situation. There were some calcium carbonate stains spread over the web, many swelling points and radial ice lens spread over the surface of box girder. The carbonization depth was over 10mm, and the rebound value of web concrete lower than 50, some areas’ lower than 35, variance larger than 30. Compared with other parts, the rebound value of web bottom concrete was the lowest and the variance biggest. For the same cross section, there were obviously difference of concrete quality between sunny face and shady ones, which enhanced the un-uniformity of element and made the stress distribution more complicated and uncertainty. Some effective measures must be taken to avoid the infant age frozen in order to assure the concrete quality constructed during the winter.

Abstract: With the comprehensive development of ultra-high voltage (UHV) engineering projects in China, traditional strength of steel can not meet the demands of UHV transmission tower because of the great height, span and load. Therefore, it is necessary to widely use Q460 equal angle steel. The deficiency of studies on related theories and tests leads to the lack of sufficient basis for its use. In this paper, experimental and theoretical researches were carried out on the bearing capacity of compression members of Q460 equal angle steel. Based on the test results, design suggestions and methods were put forward.

Abstract: This paper is focused on the experimental research of Fe-based oxygen carriers using coal ash as support material. Influence of coal ash size, foamer content, temperature on reactivity of Fe-based oxygen carrier for CO oxidation were conducted in thermogravimetry analyzer (TGA). Experimental results show that conversion of the oxygen carrier could attain 100% under 750 °C, and samples that made from mean coal ash grain size of 0.06 mm are more active than that of 0.09 mm, which prove tiny coal ash grain size can enhance reactivity of oxygen carriers. Besides, reactivity of oxygen carriers under 850 °C are lower than 750 °C for that relative high temperature would cause sintering of the Fe-based oxygen carriers.

Abstract: In this paper, the experiment about drying shrinkage of concrete using blast furnace slag as fine aggregate was introduced. In this experiment, blast furnace slag fine aggregates that were produced by two different steel factory and natural river sands that came from two different producing area were been used, and compressive strength of concrete for testing were four levels from ordinary strength level to high strength level. As results, the drying shrinkage of concrete that used blast furnace slag as fine aggregate is less than concrete that used natural river sand as fine aggregate when the mix proportion condition of concrete was identical. The relationship between drying shrinkage and age of drying of concrete that used blast furnace slag as fine aggregate could be described by same approximated curve equation that was used for the concrete using natural river sand as fine aggregate. As same as concrete using natural river sand, the drying shrinkage of concrete that used blast furnace slag as fine aggregate would decrease with decreasing of water cement ratio.