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Guo T.,Kunming University of Science and Technology | Zhou J.,PanLong Bureau of Housing and Urban Rural Construction | Liu X.N.,Yuxi Peoples Procuratorate | Shang B.,Yunnan Institute of Building Research
Applied Mechanics and Materials | Year: 2014

The highway tunnel is a relatively closed space, then large amounts of motor vehicle exhaust emissions, especially CO, resulting in air pollution in tunnel. The project construction cost, operation cost, and pollutant concentration distribution in tunnel are most dependent on ventilation scheme. Usually have air extraction and inflatable type ventilation system. In this paper, a numerical simulation based on two-phase flow is used to study the effect of double air extraction ventilation system to CO concentration distribution in large tunnel. The method can effectively track the gaseous diffusion and the results show that the CO concentration is lowest in the middle area of two vents and the exit area of tunnel. The highest area of CO concentration located in vents below area and the middle area of tunnel. © (2014) Trans Tech Publications, Switzerland.

Xiao M.-Z.,Wuhan Urban Construction Group Co. | Zhou C.-H.,Wuhan Urban Construction Group Co. | Cheng Y.,Yunnan Institute of Building Research | Feng X.-L.,Wuhan University | And 2 more authors.
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Based on the elastic foundation beam theory, the finite element method in which step excavation and support in stage is considered, is adopted to simulate the actual situation of excavation construction; and the displacement back analysis of m value of soils is carried out, according to field monitoring data, to provide reliable guarantee for predicting the deformations in succession construction stages. Firstly, support system FEM model is established by using APDL language embedded in ANSYS software. Then, the modified simplex optimization program is programmed by Matlab software, with calling the ANSYS FEM model circularly through original interface program in order to implement optimization inversion step by step. Through the calculation of deep foundation pit of Wuhan Yangtze River tunnel in Wuchang open excavation section, it is proved that the jointed programming technology based on modified simplex method can be easily and efficiently applied to the displacement back analysis and forecasting of retaining structure. Finally, an extended displacement back analysis and forecast model is established which can forecast the retaining structure displacement for the next working condition or adjacent sections based on the current condition. And the predicted results and measured results represent a high degree of fitting in the calculation example.

Li K.-G.,Kunming University of Science and Technology | Li K.-G.,Chongqing University | Wu Y.,Yunnan Institute of Building Research | Zheng D.-P.,Kunming University of Science and Technology
Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology | Year: 2013

Based on water absorptivity tests, single compression tests and shear tests of sandstone under the different times of drying-wetting cycle, the response rules of physical mechanical behaviors of sandstone to cyclic drying-wetting effect such as deformation behavior, intensity behavior and failure characteristic are analyzed systematically in this paper. The tests results show that the relation between water absorption, quality loss rate and drying-wetting cycle effect is positive related, while the relations between compression strength, elastic modulus, cohesive force, inter friction angle and drying-wetting cycle effect is negative correlated. Comparing with native state, when the times of drying-wetting cycle is 15, the decrease range of compression strength is up to 78.96%, and cohesive force and inter friction angle are also down 78.4% and 31.33% respectively. In addition, the need to point out that no matter the change trends of curves are increase or decrease, its rangeability is all "big then small", and finally tends to a constant. The failure characteristics of sandstone are also influenced by drying-wetting cycle effect: the less the test times are done, the more obvious the brittle damage characters is, conversely the stronger the ductility characters is, that is, with the strengthen of drying-wetting effect, the sandstone damage present a transformation law from brittleness to ductility.

Collier N.C.,University of Sheffield | Li X.,University of Sheffield | Li X.,Yunnan Institute of Building Research | Bai Y.,University of Sheffield | And 3 more authors.
Journal of Nuclear Materials | Year: 2015

Blast furnace slag/Portland cement composites are routinely used for immobilising intermediate level nuclear wastes in the UK. Using high cement replacement levels reduces hydration exotherm and lowers pH. Although a lower grout pH will be beneficial in reducing the corrosion of certain encapsulated reactive metals such as aluminium, the degree of slag reaction will also be lower which may result in the formation of less hydration products and which in turn may reduce the capacity to immobilise waste ions. Adding neutral salts such as calcium and sodium sulfate to the composite cement can potentially increase slag activation without significantly altering the pH of the cement matrix. Thus the corrosion of any encapsulated metals would not be affected. This paper describes some of the properties of a hydrated 9:1 blast furnace slag:Portland cement matrix containing added sulfates of calcium and sodium. The findings show that all additives caused an increase in the amount of slag that reacted when cured for up to 28 days. This produced more material able to chemically bind waste ions. Activation with gypsum produced the highest rate of slag reaction. © 2015 Elsevier B.V. All rights reserved.

Zhou L.,Chongqing University | Wang C.,Chongqing University | Li D.,Yunnan Institute of Building Research | Yin J.,Chongqing University | And 2 more authors.
Shenzhen Daxue Xuebao (Ligong Ban)/Journal of Shenzhen University Science and Engineering | Year: 2014

The workability, setting time, and mechanical properties of polymer-modified mortar with nano-SiO2 were tested. The Influence of nano-SiO2 on hydration behavior of polymer-modified cement-based materials was studied using microcalorimetry. Microstructure was observed by scanning electron microscope. The test results show that the fluidity is improved, the hydration reactions of polymer modified cement-based materials are postponed, the setting time is shortened. The interface transition zone between aggregate and cement paste, and the hydration production structure are effectively improved.

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