08 September 2014, Volume 32 Issue 25

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  • ZHU Hongqing, YANG Chengyi, QIN Xiaofeng, HE Chaonan
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    Conventional detection technologies for fire areas in integrated coal mines are time-consuming with large volumes of work, and it is difficult to directly locate the fire areas. To improve the technology, the transient electromagnetic method was applied in detecting fire zone distribution. Taking the Beizu Mine for example, this study used the TEM to conduct advanced detection and profile detection of the overlying coal bed of 9209 roadway under the condition of full space in the coal mine. Combined with geological data and conditions at the site, the advanced and section map of apparent resistivity was obtained by inversion calculation. According to the characteristics of response of the overlying coal bed, the natural fire areas were located by qualitative analysis. Practical application shows that the detection method based on transient electromagnetic method is able to locate the distribution of fire areas accurately, providing scientific basis for mine fire prevention, such as drilling exploration and grouting leakage stoppage, significantly improving project efficiency and effects.
  • GAO Junliang, GAO Yong, LUO Fengmin, DANG Xiaohong, FENG Wei, MENG Zhongju
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    To illustrate the effect of wind erosion on the grain size characteristics of the surface soil, five different land use types of Mu Us sandy land were chosen by a space-time substitution method. The soil mechanical composition and fractal dimension of top soil (0-1, 1-2, 2-3, 3-4, 4-5 cm) were analyzed through field sampling and laboratory experiments. The results show that the mass fraction of fine sand was the highest compared with that of other types of sand, and the mass fraction of coarse sand was the lowest among the five sample plots. The mass fraction of soil grains with different size fraction was in the following order: fine sand, middle sand, extremely fine sand+ silt sand, coarse sand, indicating fine sand is the main element in soil matrix composition in the studied area, and the sand has good sorting. The mass fraction of coarse sand and middle sand from high to low at different sampling depths was in the following order: 0-1, 1-2, 2-3, 3-4, 4-5 cm. The mass fraction of fine sand did not have significant difference at different sampling depths (P=0.4558), but the minimum content of it appeared at 0-1 cm. The mass fraction of extremely fine sand + silt sand at 0-1 cm and 1-2 cm was significantly lower than that at the other three layers (P=0.0126). It indicates that the evolution process from grasslands to sand dunes is a wind erosion desertification process, and the mass fraction of extremely fine sand + silt sand has been reduced. There was a highly significantly positive correlation between the fractal dimension and the mass fraction of the extremely fine sand + silt sand (P<0.0001). The fractal dimension of the five sampling plots has highly significant differences (P< 0.0001), and the order is the grassland (2.579), the newly cultivated land (2.479), 7-8 a farmland (2.361), >20 a farmland (2.100), and sand dune (1.716). Therefore, the fractal dimension could replace the soil mechanical composition to represent the degree of land desertification.
  • YANG Xiuli, CUI Chong, CUI Xiaoyu, JIA Jianping, ZHU Zhiping
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    The artificial silicate aggregate has a gradational structure with a compositional gradient. This paper discusses the shell structure reinforced composite based silicate aggregate core. The interface between the shell and the core nakes them to form a whole by the hydration product overlap. The performances of the SAAC aggregate and the FAAC aggregate are compared, and it is shown that the shell structure could improve the cylinder compressive strength (CCS) of the artificial silicate aggregate. The CCS of the SAAC aggregate is enhanced by 49.72%-80.50%, and the CCS of the FAAC aggregate is enhanced by 15.30%-25.74% with the shell structure. The best weight ratio of the shell and the core is 1:25, with shell thickness of 68.09 μm. The CCS of the artificial silicate aggregate with the shell structure is enhanced by about 25% as compared with that without the shell structure. Compared the silicate aggregate concrete with the ordinary concrete in the same level mortar and volume of the aggregate, it is shown that the compressive strength of the silicate aggregate concrete is 6.38% lower than the ordinary concretes, and the apparent density of the silicate aggregate concrete is 20.74% lower than the ordinary concrete.
  • LUO Qingwei
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    The SrTiO3 films prepared by chemical method possess features of low-cost and efficiency, and they are a promising buffer layer for YBCO coated conductors. STO buffer layers were prepared on Ni-5W substrate by chemical solution deposition. Acetate and tetrabutyl titanate were used as precursors to synthesize the precursor solutions of STO seed layers, LaxSr1-xTiO3 seed layers and STO buffer layers. Effect of the thickness of STO seed layers on the properties of SrTiO3 epitaxial films prepared on STO/Ni-5W(200) structures was studied. The results showed that three multilayer STO seed layers were sintered at 880℃ which was favorable to fabricate (200)-oriented STO films with smooth surface. When La was added into STO, stabilized LSTO precusor solution could be obtained, and highly (200)-oriented STO buffer films were prepared on LSTO/Ni-5W structures. They can be a promising buffer layer for YBa2Cu3O7-δ coated conductors.
  • QIN Fang, JIANG Qinfeng, AI Yuming, ZHANG Yao, CAI Cancan
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    As most clay minerals are negatively charged, they need to be modified to improve the algae removal capacity, which, however, leads to increased cost and secondary pollution. Therefore, this paper explores the feasibility to use positively charged clay minerals for algae removal. Mg/Al hydrotalcite (Mg/Al-LDH) was synthesized by co-precipitation method and its calcination product (Mg/Al-LDO) was prepared by heating Mg/Al-LDH at 400℃. To know the practical applicability, a detailed study of Microcystis aeruginosa removal was carried out. The influences of sorbent concentration, stirring time, solution pH, and initial Microcystis aeruginosa concentration were investigated. The results indicate that the removal of Microcystis aeruginosa was the highest using 1 g/L of Mg/Al-LDO under pH 6-11 with stirring time of 1.5 h. Mg/Al-LDO had relatively high removal capacities at the initial Microcystis aeruginosa concentration range of 0.5~3.0 mg/L.
  • CAO Yuan, DENG Jingen, YU Baohua, FAN Baitao, ZHAO Kai, XU Yongmeng
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    The wellbore instability of a fracture shale formation is an issue often encountered in drilling. A fracture formation of the hydration property is often associated with severe borehole collapse. The shale beddings are actually micro-fractures according to the microstructure observations by SEM. The content of the clay minerals of the shale is 30%-40% determined by XRD equipments, and shows a strong hydration property. The shearing strength of the shale is tested by shear experiments, the cohesion and the internal friction angle are determined under different water contents, and the results are regressed. Based on the Darcy linear percolation law, the seepage equation for the drilling fluid is obtained. Through the well circumferential stress analysis and combined with the above results, the collapse equation is obtained. Collapse pressures are calculated under different mud densities and soak times. The calculation results show that the high density drilling fluid accelerates the seepage with increased water amount and reduces the strength against fracture, which leads to more easy formation collapse. Improving the drilling fluid density is unfavorable for the wellbore stability of the fractured shale formation. Measures should be taken to improve the drilling fluid plugging ability and the inhibitory ability, reducing the amount of mud filtrate invasion.
  • ZHANG Deping, ZHAO Yao, SHI Xiaohui, LIU Zhenyi
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    Greenhouse effect and energy shortage are becoming increasingly serious problems with rapid development of the oilrefining industry. Oil carbon capture and storage and the enhanced oil recovery(CCS-EOR)is developed to alleviate the shortage. Asimulation was carried outusing CFD method in this paper. The FLUENT software was used, and the SIMPLEC method and standard turbulent model were adopted to solve compressible N-S equations. VOF (volume of fluid) model was chosen as the multiphase model. The numerical simulation was based on the physical model and suitable mathematical model. A model was established to illustrate the mechanism and rule of supercritical CO2 BLEVE, providing technical support to accident prevention and reference for future research.
  • DING Yunhong, ZHANG Qian, SHI Lei, SUN Junchang, JIANG Shuai
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    The carbonate condensate gas reservoir in North China features great burial depth and medium water invasion. It possesses complex development characteristics and percolation mechanism, leading to difficulties in parameter optimization of the storage capacity. The characteristics of the pore throat structure in the carbonate reservoir were studied based on the comparative analysis of capillary pressure curve and T2 spectrum in nuclear magnetic resonance. The gas-water two-phase percolation law in the micro-crack carbonate reservoir was analyzed by studying the gas-water two-phase relative permeability curve using non-steady state method. The results show that the carbonate condensate gas reservoir in North China has developed micro-fracture, narrow pore throat and concentrated distribution, the gas seepage characteristics vary in different layers, and all the factors have great influence on the construction and injection-production operation efficiency of gas storage. The characteristic evaluation provides theoretical basis for planning for construction and injection-production optimization.
  • WANG Weichao, ZHANG Wujiao, LIU Xiliang, WANG Li, LI Huigui
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    Brazilian split tests for salt rock were carried out with a servo-controlled test machine RMT-150B, and acoustic emission (AE) detections were conducted at the same time. The results indicate that the deformation characteristics before the peak load in Brazilian split tests are similar to those of uniaxial compression test which could be divided into four stages, namely compression, elasticity, yielding and failure stage. AE events in compression and elasticity stage are totally low in energy and accumulation number. Starting from the yield stage, AE events increase rapidly, and energy and accumulation number grow quickly. The specimens suddenly fracture when the load exceeds capacity, and the residual stress rapidly disappears. In this test, the sign for specimen failure could be judged through observing ringing counting, accumulation number and energy, so as to provide reference for engineering practice.
  • ZHANG Chong, ZHANG Zhansong, CHEN Yulong, XING Yanjuan, LI Chaowei
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    Taking the sandy conglomerate reservoirs of Denglouku and Yingcheng Formations in Xiaochengzi area, Wangfu Fault as an example, the logging lithology identification is studied in this paper. Based on the logging lithology data, various lithologic compositions of objective intervals are analyzed and the main lithology components of Denglouku and Yingcheng Formations are extracted firstly. The main components of Denglouku Formation are the sandy conglomerate, the sandstone and the shale and those of Yingcheng Formation are the conglomerate, the sandy conglomerate and the shale. Then the logging response characteristics are analyzed, the lithologic parameters of these two formations are extracted and it is shown that the sensitive parameters of Denglouku Formation are the natural gamma ray (GR), the neutron (CNL),the interval transit time (AC) and the resistivity (RT) and that the parameters of Yingcheng Formation are the GR, the density (DEN) and the CNL. Finally, the Fisher model of the lithology identification is established by using the SPSS software, and the application of the model to the reservoir lithology identification of five wells not included in the process of building the model shows that the discriminant accuracy rate reaches 86%, which indicates a high reliability of the method.
  • SHI Xiaozeng, WU Jiazheng
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    With the development of urban construction, tunnels with vertical shafts have been increasingly used in urban traffic tunnels. In this paper, steady and unsteady methods are used to simulate the airflow field of vertical-shaft type tunnels under fire conditions. The effect of vertical shaft natural ventilation opening on high temperature gas diffusion is analyzed. It is found that natural ventilation of vertical shafts introduces cold air outside the tunnel, significantly lowering the fire source temperature, to some degree reducing the damage of high temperature smoke and gases to the tunnel roof at the fire source. The introduction of fresh air also significantly lowers the concentration of toxic gases near the fire source, improving the rescue condition. The centralized discharge of toxic smoke and gases at the opening of tunnel terminal is changed to decentralized discharge at the natural ventilation opening of vertical shafts, which provides important guide for fire rescue and evacuation planning. The natural ventilation plan could meet the demand of fire escape.
  • LIU Xiaodong, ZHAI Xingran, SUN Yanbo, REN Yuan
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    This paper develops an evaluation system of atmospheric environmental quality using SuperMap IS.NET5 as the development platform, SuperMap as the technology platform, SQL Server2005 as the database platform, C# which is an object-oriented programing language as the development language, and Microsoft VS.net as the development environment. The evaluation system was used to evaluate the atmospheric environmental quality in Daqing. The results show that the evaluation system has many features, such as easy management, real time, good compatibility, data query, and statistic analysis. The evaluation rank is precise, reasonable, objective, and consistent with real circumstances. The system improves the evaluation speed and effects by exporting the results directly on maps, providing overall, real time, and precise guide for decision-making of related government sectors for environmental protection.
  • MA Shibin, YUAN Wenrui, WANG Qingzhou, ZHANG Caili
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    Considering the large variety of design parameters and wide range of values of long-life asphalt pavement structure, this paper analyzes the influence of the modulus and thickness of each layer on the tensile strain at the bottom of asphalt concrete layer (εt) and the compressive strain at the top of the subgrade (εz) using the KENPAVE software. The significant influencing factors of εt and εz were further studied by the response surface methodology (RSM), and a correlation model was presented. The analysis results show that intermediate layer thickness, base layer thickness, subbase layer thickness exerted significant influence on εt and εz, intermediate layer modulus and base layer modulus exerted moderate influence, and εt and εz were optimized when 16 cm of intermediate layer, 1800 MPa of modulus, 6 cm of base layer thickness, 1200 MPa of modulus, 40 cm of subbase layer thickness were chosen. The test results may provide a reference for future studies of structure optimization of long-life pavement.
  • Reviews
  • FENG Xingguo, CHEN Da, LU Xiangyu
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    This paper reviews the main characterization methods for studying passive behavior of rebar, introducing the application of open circuit potential (OCP), cyclic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky plots, X-ray photoelectron spectroscopy (XPS), andmicro-Raman spectroscopy (μ-Raman) in passive behavior of rebar in concrete environments. In addition, the influence of Cl- ions, pH of solution, and stress on the passive behavior of rebar in concrete environments is discussed.With the increase of Cl- concentration and stress, or decrease of solution pH, the passivity of rebar degraded and the rebar was more susceptive to corrosion. Finally, further research prospect is presented.