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.
Wang Y.-N.,Beijing Jiaotong University |
Wang Y.-N.,China Civil Engineering Construction Corporation |
Chen X.,Beijing Jiaotong University |
Wang D.-Y.,Beijing Jiaotong University |
Yu Y.-Z.,Tsinghua University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2016
To study the effect of soil deformation, the soil-water characteristic curves (SWCC) are tested using VJ Tech consolidation apparatus with the initial void ratio taken as the deformation index. The test results show that in low suction range the effect of the initial void ratio on SWCC is significant, while in high suction range the effect is not remarkable. By introducing the void ratio into the model parameter related to the air entry value, a new soil-water characteristic surface (SWCS) model is proposed based on the Fredlund-Xing model so that the new model can be utilized to predict the varied coefficient of permeability during soil deformation. The new model is also applied to the seepage analysis of a soil dam with core wall, and it is found that for different degrees of compaction, the seepage flow flux is dependent on the saturated coefficient of permeability or is proportional to e3/(1+e). © 2016, Editorial Office of Chinese Journal of Geotechnical Engineering. All right reserved.
Zhang W.,Jilin University |
Chen J.,Jilin University |
Wang Q.,Jilin University |
Yan J.,Jilin University |
And 3 more authors.
Quarterly Journal of Engineering Geology and Hydrogeology | Year: 2015
This paper focuses on a model that predicts the runout and velocity of the Dongwopu debris flow in Tianjin, China. Based on the law of energy-conservation, the established model primarily considers potential energy and energy loss in debris-flow movement. The present study discusses several stresses that could cause energy loss for debris flows, and the friction energy loss is emphasized. Ultimately, the analytical expressions of runout and velocity are established. The calculation results show that the velocity of the Dongwopu debris flow is 14ms-1. At this velocity, the runout distance will not cause a threat to residents and engineering facilities in the area. © 2015 The Geological Society of London.
Zhang H.-Y.,Beijing Jiaotong University |
Zhang H.-Y.,China Civil Engineering Construction Corporation |
He P.,Beijing Jiaotong University |
Yan G.-X.,China Xinxing Baoxin Construction General Corporation |
And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2016
The shield tunneling adjacent to bridge pile foundation has become a hot issue at present. In view of the application value of parameters of shield tunneling in projects, the vertical additional stress of the pile foundation is analyzed by using a three-dimensional elastic-plastic finite element method. The mathematical expressions for pile length and proportional coefficient are derived. The radii of impact area and non-impact area of piles are defined by comparing the influence area of additional stress generated by piles with the influence radius put forward by Randolph. The optimal values of tunnel face pressure and grouting pressure in the non-impact area of piles are obtained through three-dimensional elastic-plastic finite element analysis based on the theoretical values of tunnel face pressure and grouting pressure. The expression for calculating the ground loss is introduced under the condition that the soil loss per unit length equals the area of settlement trough. By combining the optimal values of the parameters of shield tunneling in the non-impact area and the additional stress generated by piles, the mathematical expressions for the parameters of shield tunneling in the impact area are achieved. The results show that when the soil pressure resistance of tunnel face equals the static soil pressure of tunnel face and the grouting pressure equals 1.1 times the soil and water pressure on the top surface of tunnel, the disturbance of the soil strata is relatively slight. © 2016, Editorial Office of Chinese Journal of Geotechnical Engineering. All right reserved.
Liu Y.-F.,Tianjin University |
Liu Y.-F.,China Civil Engineering Construction Corporation |
Li J.-L.,Tianjin University |
Li J.-L.,China Civil Engineering Construction Corporation |
Xu S.-H.,Tianjin University
Gongcheng Lixue/Engineering Mechanics | Year: 2012
CDM (Consolidation decelerating ground treatment method) is a new ground treatment method which eliminates later ground consolidation settlement and controls the post-construction settlement by confining the pore pressure dissipation of the ground during the operation service period. CDM is refined by setting a deep horizontal anti-seepage layer and the research is based on it. Finite element method calculation shows that the post-construction settlement of ground treated by CDM decreases with the increase of depth of anti-seepage curtain, but no more decrease will occur when anti-seepage curtain is deep enough, while CDM with very shallow anti-seepage curtain results in larger ground post-construction settlement than natural ground. Comparisons of excess pore pressure distribution, vertical displacement field distribution, settlement time process curves and ground post-construction settlement controlling effect between a rigid pile and CDM are made by the finite element method, also, economy of the two methods is compared simply. CDM does can reduce ground post-construction settlement with a feasible depth of the anti-seepage curtain. CDM is better than the rigid pile on economy and technology with the treatment depth within a certain limit.
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.
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.
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.
Xie X.,China Civil Engineering Construction Corporation
Applied Mechanics and Materials | Year: 2012
In the construction of an overpass transversal to an existing electric railway, when the overpass pier is door-shaped, and, when the clearance height from the bottom of the door-shaped pier cap beam to the contact wire electrified body is too small to use steel beam or I-beam for holding the formwork and meet the safety need prescribed by the Ministry of Railways, an innovative construction method was employed, in which D-type steel beams, originally used for railway track reinforcement, was lifted to get across the contact wire and the catenary from above with a gap more than 33.8cm, resting on the top surface of temporary buttress, and letting stocky horizontal beams hold the formwork of cap beam, so as not to affect the normal operation of the existing electric railway. This innovative technique has been granted patent for invention by the State Intellectual Property Office. © (2012) Trans Tech Publications, Switzerland.