Deng H.,Chinese Research Institute of Highway |
Zhou Q.,China Civil Engineering Construction Corporation
Modern Tunnelling Technology | Year: 2013
In light of the current reality of road tunnel construction, the sub-classification index system, which takes rock hardness and integrity as a basic index and groundwater status and occurrence of main weak structural surface as a correction factor during tunnel construction, is established by summarizing the indexes of a variety of surrounding rock classification methods at home and abroad. A sub-classification model was also set up based on quantification theory. The sample test demonstrated that this model is highly accurate and rational. Combined with programming techniques and database technology, a computer-aided sub-classification system of surrounding rock was finally developed, which basically realized automatic and intelligent management of the sub-classification.
Zhang Y.-Q.,Nanjing University of Aeronautics and Astronautics |
Zhang Y.-Q.,Nanjing Agricultural University |
Yu H.-F.,Nanjing University of Aeronautics and Astronautics |
Sun W.,Nanjing Southeast University |
Zhang J.-Y.,China Civil Engineering Construction Corporation
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2011
Through the method of accelerated freeze-thaw, the freeze-thaw durability of three kinds of concretes subjected to water and 5% (by mass) MgSO4 solution was studied. The concretes studied include high strength concrete (HSC), high-volume mineral admixture concrete (HVMAC) and high durable concrete (HDC) with high-volume mineral admixture, air-entraining agent, superplasticizer, fibers and expansion agent added. Results show that for higher water binder ratio, lower content of mineral admixture of HSC, MgSO4 solution can significantly alleviate the freeze-thaw damage because of lowering effect of MgSO4 solution freezing point. Chemical corrosion products fill the pores in the concrete surface to protect and strengthen. For lower water binder ratio of HVMAC, MgSO4 chemical reaction leads to formation of expansion products, such as magnesium hydroxide and gypsum, etc., which further promote the internal formation of AFt by freezing and thawing, leading to the propagation and coalescence of micro-cracks, but the freeze-thaw damage of HPC is accelerated. Based on low water cement ratio of HVMAC of preparation techniques, the frost resistance of HDC, especially under the corrosive action of MgSO4, prepared by highly efficient air-entraining, hybrid fibers and expansive agent can be significantly improved. Freeze-thaw cycles of HDC is 625 times in water, and more than 900 times in 5% MgSO4 Corrosion solution.
Xie X.,China Civil Engineering Construction Corporation
Advanced Materials Research | Year: 2012
In order to resist the landslides at the Chongqing-Huaihua Railway, A new 82m long open cut tunnel is constructed under normal operation of the railway, in spite of the HV contact wire overhead and tracks below the line. The tracks are reinforced by suspending every other track panel, so that construction of the open cut tunnel foundation under the ballast bed can be executed without affecting safe operation of the railway; arch-shaped steel pipe supports are used to decrease the interchange of HV contact wire during the construction without affecting normal operation of the railway; arch lining trolley is created to lift, slide and be electricity-proof, so that the work above the contact wire would not contact with the wire, and construction of arch ring and changing formwork would not be obstructed by normal operation. These new and creative schemes and techniques may provide approaches to constructing open cut tunnels for electric railways.
Chen Z.-H.,China Civil Engineering Construction Corporation
Journal of Railway Engineering Society | Year: 2013
Research purposes: With gradual popularization of the European norms in the world, the European structural standards in particular in the norms have progressively shown characteristics as international general standards. Although the Chinese railway has set up its own system of specifications, however, to further develop and popularize its specifications in both China and the world, Chinese railway needs to follow the modern international scientific achievements and familiarize itself with the characteristics of the system of the European norms and master them for application. Research conclusions: From the research on the choice of the European bridge specifications, the author reveals the following findings: (1) The new version of the European specifications, which resulted partially from deletion and combination of relevant contents of the old version and was edited with layout according to professional codes, has optimized systematization and methodization of the system. (2) Values range and calculation methods have been stipulated for various parameters on train load, derailment load, traction-braking load, wind load, etc. for railway bridge design according to the new specifications system. (3) The ultimate-limit design based on complete probability is adopted for the European specifications. Being different from the Chinese specifications, its anti-seismic design is arranged in two stages for seismic fortification with an effective checking-calculation method, i.e. linear analysis and time-lapse technique. (4) The above-stated choice of various parameters for railway bridge design under the new specifications system and the main differences on bridge design between the European and the Chinese specifications may provide valuable reference to the Chinese engineers who intend to adopt the European specifications for bridge design.
Li M.,Chinese Academy of Agricultural Sciences |
Li M.,Key Laboratory of Farm Building in Structure and Construction |
Zhou C.,Chinese Academy of Agricultural Sciences |
Zhou C.,Key Laboratory of Farm Building in Structure and Construction |
And 6 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2016
In this study, a polystyrene-brick composite wall, which is composited with the polystyrene-brick filled with concrete, soil and concrete board, was developed to be the north wall of the Chinese solar greenhouse (hereafter referred to as "solar greenhouse"). The purpose of this study is to investigate the heat insulation and storage performances of the polystyrene-brick composite wall and to analyze the feasibility of substituting for the clay-brick sandwich wall. The tested solar greenhouse was located in Yongqing county, Langfang city, Hebei province(116°35′ E, 39°18′ N). It was 80 m long and 10 m wide. The north wall was the polystyrene-brick composite wall composited with 24cm polystyrene-brick filled with concrete, 45 cm soil and 5 cm concrete board in the direction from exterior to interior. The polystyrene-brick, which was made with polystyrene, was 24 cm wide with a 12 cm-wide cavity. The test period was from Dec. 20, 2013 to Jan. 30, 2014. During the period, the tested solar greenhouse was used to growing zucchini and employed drop irrigation. The heat insulation sheet was rolled up and down at 8:00 and 16:30, respectively. The wind vent would be open if the indoor air temperature was high during daytime. The indoor and outdoor air temperatures, solar irradiating on the inner surface of the wall, the inner surface temperature and soil temperature in the wall were measured. The data collected in a typical cloudy day (from Dec. 25, 2013, 8:00 to Dec. 26, 2013, 8:00) and a typical sunny day (from Dec. 28, 2013 8:00 to Dec. 29, 2013, 8:00) were used to analyze the heat performances of the polystyrene-brick wall. Then, the inner surface temperature of a clay-brick sandwich wall, which was composited with 24 cm clay-brick, 10 cm polystyrene board and 24 cm clay-brick, was simulated with one-dimension differential model to analyze the feasibility of substituting for the clay-brick sandwich wall. During the period when the solar greenhouse was covered with heat insulation sheet, the inner surface temperature of the polystyrene-brick composite wall was (2.5±0.2)℃ and (5.4±1.4)℃ higher than the indoor air temperature in the cloudy day and the sunny day, respectively. It is indicated that the heat released by the wall into the solar greenhouse during the nighttime of the sunny day was 2.1 times than that during the nighttime of the cloudy day. As a result, the indoor air temperatures in the nights of cloudy day and sunny day could be maintained at (9.8±1.1)℃ and (13.0±2.1)℃, which were (15.1±2.0)℃ and (22.6±1.1)℃ than the outdoor air temperature, respectively. The results meant that the solar greenhouse can meet the requirement of most crops. According to the simulated and measured results, the differences in the inner surface temperature between the clay-brick sandwich wall and the polystyrene-brick composite wall were less than 0.3℃. On the other hand, the heat release region of the polystyrene-brick composite wall in the cloudy day and sunny day was 17 cm and 33 cm, respectively, and both were smaller than the thickness of soil and concrete board. It is indicated that the thickness of soil and concrete was large enough for storing heat in the daytime. Besides, the heat resistance of the polystyrene-brick filled with concrete was estimated as 2.93 m2 K/W. It was two times of the lowest heat resistance of the wall in local solar greenhouse. Thus the heat resistance of the polystyrene-brick composite wall was large enough to prevent heat in the soil from flowing to the outside. Finally, it is concluded that the polystyrene-brick composite wall is feasible to be the north wall of the solar greenhouse and feasible to substitute the polystyrene-brick composite wall for the clay-brick composite wall. © 2016, Chinese Society of Agricultural Engineering. All right reserved.