Applied Mechanics and Materials Vols. 71-78

Abstract: For the conditions of coal seam with huge thickness, structural complexity and intrusion by pyrolith in Datong carboniferous period, using laboratory similar simulation, on-site deep basis points observation and working face coal caving measurement, it is found out the migration and release laws of top coal, developed a practical caving technology. It has a good economic efficiency, and it is great significance for similar mining area to mining coal seam with huge thickness.

Abstract: In order to study the transverse reflection crack of concrete composite lay in old bridge reinforcement, aiming at the forming process of the reflection crack, the theoretical model of its peak tensile stress and its separation distance is presented, and its forming mechanism is analysed. Based on the theoretical model, the influence of the thickness overlay, and constraint under the concrete composite lay are studied to the transverse reflection crack. Based on these researched results, the peak tensile stress and its separation distances is calculated by given theoretical model , and the results reveal shrinkage cracks rely on the restraint condition , elastic modulus, shrinkage ratio and the thickness of the composite-slab.

Abstract: This study presents a practical requirement and realizes one new virtual construction interactive system for tunnel boring machine. One type of TBM(tunnel boring machine)’s virtual prototype has been built. Software PROE is used to build the shield machine model. Application program of virtual assembly system base on virtual reality is developed by using Division, The author also study on key technologies of constructing virtual assembly system of shield machine, such as interference detection in virtual environment. Application program of virtual simulation system base on virtual reality is developed by using C++. The result shows that the work station can be simulated well, and this virtual simulation system can be extended in virtual training and manipulation, virtual construction and so on.

Abstract: To recognize the interrelationship of plastic deformation with strain and time, uniaxial tension relaxation experiments of PVC coated plain weave membrane were executed along the warp and weft direction, while plastic deformation of the specimen were measured in 1 year. Using multiple functions from the product of both the strain difference (strain- critical strain) power function and the time power function, the experimental data was studied on a multiple regression analysis. It was concluded that the model had better fitting results. At the same time, an instantaneous plastic and a relaxed plastic term of the total plastic deformation were analyzed. It was showed that the instantaneous deformation was the main part of the plastic deformation, that the relaxed plastic deformation was the minor part of the plastic deformation, and the relaxed plastic deformation would become smaller and smaller with time extension.

Abstract: In severe cold area, the exterior layers of envelope usually experience seasonal freezing /thawing due to cold climate in winter. However, it can lead to severe problems especially in the newly-completed building. In order to analyze the drying of envelope on building initial use, the heat and moisture coupled transfer of building envelope in severe cold area Harbin, China was simulated with the modeling method developed. The modeled result was analyzed. It is concluded that the drying rate of the newly-completed building envelope is significantly high in the first year, especially in the first few months. Insulation performance of the wall in the first winter is most serious due to the high initial moisture and freezing ice content in insulation layer. For the simulated envelope, the freezing of the moisture content especially that in insulation layer had notable effect on heat transfer coefficient (thermal resistance), and the maximum of heat transfer coefficient of the modeled envelope in the first year winter is about 7% higher than that in the tenth year, which is taken as final hygral state.

Abstract: Several viewpoints of vacuum preloading mechanism were analyzed. Action process of vacuum preloading was compartmentalized three phases. They were seepage consolidation in shallow soil and “surcharge” effect in deep soil by vacuum suction, consolidation stabilization in the shallow soil and transformation of “surcharge” to “negative pressure” in deep soil, seepage consolidation in deep soil under “negative pressure” and to balance. Action mechanism root of vacuum preloading was not negative pressure difference solely, which was produced by seepage field. The root was “positive pressure” and “negative pressure” together during different stage. The root also included the two pressures superposition under the especial phenomenon of vacuum preloading: water level falling. Under the mechanism, stress of soil was analyzed. Effective stress path began from line resembling that under surcharge in q-p plane. It would never reach line and after a short period it would develop paralleling p-axis. Horizontal contractive displacement of soil took place because “negative pressure” intensity was much stronger than “positive pressure” intensity. If surcharge effect equal vacuum preloading effect, soil under vacuum preloading reached yield more difficultly. Last, measured value was analyzed and the analysis of mechanism, stress was validated.

Abstract: The construction technical management occupies an important place for ensuring the construction quality in the project construction activities. Its tasks cover: correctly carry out the State’s technical policies, supervision procedures, technical specifications and standards; rationally arrange the construction work procedures in conformity with scientific laws; properly develop the technical programs for construction work; provide complete basis and execution evidence for technical work and ensure that the construction quality is in compliance with the requirements of design documents, applicable standards and the contract. So we must normalize the construction quality management work of project and guarantee the construction quality of the project.

Abstract: In this paper, by studying the engineering properties of rubber particles-improved fly ash soil, the authors provide technical parameters for setting up cold-resistance layer in the seasonal frozen zone. In the experiment, rubber particles are mixed into the fly ash soil by mass of 0%, 1%, 2%, 3%, 5% and 7% and unconfined compressive strength testing, frost heave test, insulation test and thermal conductivity test. By analyzing the test results, the authors drew the conclusion that fly ash soil improved by rubber particles has a high compressive strength, a small amount of frost heave, good insulation performance, small thermal conductivity coefficient.Therefore, improved fly ash soil with rubber particles is one of the preferred materials to set up the cold resistance layer in seasonal frost zone.

Abstract: Water sand and gravel stratum is characterized by high gravel content, big grain size and high strength, easy permeation for water and air, brittleness and hysteresis quality in stratum failure, causing great difficulties in EPBM hyperbaric intervention and changing cutter tools working under air pressure. Due to the special geological conditions and no useful reference or criterion about gas permeability in such stratum all over the world, gas permeability test is done to fetch air loss data in natural state and bentonite-added state.Based on the practical situation of ChengDu Metro Line 1-Lot 3 project, by using methods of site test and theoretical analysis,the air loss before/after bentonite is added are given: At the air pressure of 1.0 bar, the air loss with bentonite added is 27% of that without bentonite. The acreage of pressure air loss around excavation face is from 35.2 m² (In case of half chamber muck and bentonite slurry is 100% in effect around shield machine) to 129.6m² (In case of empty chamber and bentonite slurry is 50% in effect around shield machine), providing reference in choosing air compressor, also for other project in this stratum and similar project.

Abstract: Polystyrene microspheres were prepared by the emulsifier-free polymerization method. Using the polystyrene microspheres as seeds, p-nitroaniline as template molecules, the monodispersed molecularly imprinted polymer microspheres (MIPMs) were prepared by a single-step swelling and polymerization method. The monodispersed molecular imprinted polymers with porous structure were characterized by SEM, and UV-visible spectrophotometry. The adsorption performance of MIPMs for p-nitroaniline was investigated.