18 March 2013, Volume 31 Issue 8

    

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  Association of Energy Characteristics and Meso-structure of Rock

  ZHANG Zhizhen;GAO Feng;CUI Yang;LIN Bin

  . 2013, 31(8): 20-26. https://doi.org/10.3981/j.issn.1000-7857.2013.08.001

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  The meso-structure of rock affects its energy behavior during loading process. From three meso-characteristics, that is, mean strength of rock element, homogeneity, and meso-characteristic scale, their influential rule involving five characteristic energy parameters as well as four energy characteristic indexes is discussed. The results show that (1) with the increasing the mean strength of rock element, the input energy density and elastic energy density go up nonlinearly while stress ratio is same; the dissipated energy after peak strength changes a little, about 500～2000J/m³; conversion rate to elastic energy decreases; energy characteristic indexes of rock sample increase exponentially. (2) As the homogeneity raises, the input energy density and elastic energy density before peak strength increase linearly; the dissipated energy after peak strength reduces; more and more input energy translates into elastic energy accumulated in rock; the energy characteristic indexes enlarge linearly. (3) The larger the meso-characteristic scale is, the more the input energy and the elastic energy with different ranges is; the more the dissipated energy after peak strength is, the lower the conversion efficiency into elastic energy is. The energy characteristic indexes decrease by a large margin when meso-characteristic scale is smaller than 1mm and decrease only a little when meso-characteristic scale is larger than 1mm.
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  Broken Mechanism of the Bolt Tail and Applications of Anti-breaking Methods

  LI Xibing;MA Shaowei;MA Chunde;LI Jinyue;GUO Yang

  . 2013, 31(8): 27-31. https://doi.org/10.3981/j.issn.1000-7857.2013.08.002

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  Based on the bolt impacted by the elastic energy of rock mass and the stress solution that a rigid block collides with rod along axially in impact dynamics is adopted; four stress conditions of rock mass are derived before the bolt is fractured. And on the basis, several factors, including elastic modulus of rock, elastic modulus of bolt, diameter of bolt, and Poisson's ratio of rock, are discussed. The analytical results show as follows: In four stress conditions of rock mass, it is impossible that bolt head is directly fractured, but the rest parts have high possibility. In addition, the rest bolts have the similar stress conditions of rock mass, therefore it has a high possibility that the bolt tail is directly fractured, it also confirms with the view that bolt tail is easily broken; Besides, before the bolt is fractured, the stress condition of rock mass is affected by several factors, including elastic modulus of rock, Poisson's ratio of rock, density of rock, elastic modulus of bolt, density of bolt, and diameter of bolt, among them elastic modulus of rock, elastic modulus of bolt, diameter of bolt, and Poisson's ratio of rock exert the greatest impact; the stress condition of rock mass before the bolt is fractured has the theoretical significance for improving the anchor form and optimizing mechanical properties of bolt. Finally, a tunnel engineering in the mine of Ma Luping is given to explain how to use the anti-breaking methods for bolt in practice and the ideal results are obtained; therefore these methods are able to be applied to the actual engineering.
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  The Impacts of Different CO₂ Injection Temperatures on Heat Extraction Rate in CO₂-Enhanced Geothermul Syatem based on the CCS Demonstration Project in Erdos

  WANG Fugang;NA Jin;GENG Xinxin

  . 2013, 31(8): 32-37. https://doi.org/10.3981/j.issn.1000-7857.2013.08.003

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  Majiagou geologic formation in Erdos Carbon Capture and Storage (CCS) demonstration project is chosen as artificial geothermal reservoir, the simulation software of TOUGH2 is used to create numerical models of Enhanced Geothermal System (EGS) in which CO₂ is heat transfer carrier. In order to analyze the impact of CO₂ injection temperatures on heat extraction rate and the sustainability of CO₂-EGS, five cases with different CO₂ injection temperatures ranged from 18℃ to 42℃ are designed. Simulation results show that the range of the average heat extraction rate for those five cases is 6.56～8.47MW in the entire period of CO₂-EGS operation. The heat extraction rates vary over time and the rate is 6.37～7.9MW in the stage of CO₂ and water displacement and the rate is 6.64～8.68MW after aqueous phase disappear, respectively. In whole process of CO₂-EGS, the temperature of production fluid decreases with a rate of 1.89～1.74℃/a and the system sustainable time is 10.58～11.49a. Injection temperature of CO₂ significantly impacts the heat extraction rate of EGS; however has a little impact on the sustainability of CO₂-EGS. Reducing CO₂ injection temperature in the range permitted by the CO₂-EGS operation is a good choice for CO₂-EGS. Those results could provide the reference for the geological storage and resource utilization of CO₂.
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  The Reservoir Protection Mechanism of Underbalanced Drilling Operation

  ZHANG Guangyin;ZHAO Xiangyang;YANG Shunhui;DOU Ninghui;XIA Bairu

  . 2013, 31(8): 38-41. https://doi.org/10.3981/j.issn.1000-7857.2013.08.004

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  The current research status on the underbalanced drilling operation at home and abroad is systematically summered. The reservoir damage mechanism and during the normal process of underbalanced drilling operation, the reason making well bottom reservoir run into intermittent overbalanced drilling operation status caused by drilling operations, such as tripping, logging, and well completion, are analyzed. Intermittent overbalanced drilling operation causes the seriously reservoir damage due to the intrusion of the solid phase, water trapping, and water sensitivity. The technology and the reservoir protection mechanism of underbalanced drilling operation from open reservoir to reservoir production are discussed. Finally, the advantages of underbalanced drilling operation, involving reservoir protection, the reduction of lost circulation and other drilling accident, production increase, quick, real, and exact discovery of reservoir, and evaluation of reservoir, are illustrated by taking wells QX3 and QX4 as the example.
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  Productivity Formulae of Branched Horizontal Well in Ribbon-Shaped Gas Reservoir in Sichuan-Chongqing Region: Promoting of Qi Cheng-wei's Formulae

  CHEN Pengye;CHEN Jun;ZOU Xianfeng;HOU Jun;LIANG Haijun;LI Na

  . 2013, 31(8): 42-45. https://doi.org/10.3981/j.issn.1000-7857.2013.08.005

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  Qi Chengwei's formulae consists of the two formulae for predicting horizontal well productivity, proposing at first time in the world; the formulae is only for the prediction of ribbon-shaped petroleum reservoir, but not for the prediction of natural gas reservoir. In order to predict the productivity of branched horizontal well in ribbon-shaped gas reservoir in the Sichuan-Chongqing region, according to the similarity principle between gas seepage and liquid seepage and the relationship between gas relative permeability and sulfur saturation summed up by Roberts, the famous Qi Chengwei's formulae are successfully generalized to pseudo three-dimensional productivity formulae of horizontal well in ribbon-shaped sour gas reservoir. On the basis of the revised formulae, the impact of sulfur deposition amount and permeability anisotropy coefficient on productivity is analyzed, and important knowledge that the effect of sulfur deposition amount on productivity is greater than that of permeability anisotropy coefficient is obtained and longitudinal bilateral horizontal well possesses more advantages than transverse horizontal well in ribbon-shaped sulphuric gas reservoir. At last, a proposal that the pseudo three-dimensional productivity formula derived by Qi Chengwei for radial branched horizontal well in circular petroleum reservoir should be promoted to sulphuric gas reservoir is put forward.
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  The Impact of Shapes of Thermowell on Its Vibration and the Force on It

  SUN Jiren

  . 2013, 31(8): 46-50. https://doi.org/10.3981/j.issn.1000-7857.2013.08.006

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  Thermowell may take various forms in engineering applications, such as tapered, straight, and step-shank forms. The thermowells of different shapes have their own characteristics, including their natural vibration frequencies and the stress distributions. The selection of the thermowells shape should be based on the vibration characteristics and the stress distributions. In the past, the designer are eager to learn about the characteristics of different shapes thermowell, but due to lack of analysis of vibration frequency for different shapes thermowell, therefore, in the engineering design, selection of thermowells shape seemed more random. In recent years, with increased discussion and further research on the issue of themowell vibration and stress makes possible to study shapes impact on vibration and stress of thermowell. Based on the ASME PTC19.3 TW-2010, this paper makes analysis and comparison of the natural vibration frequencies and the stress distributions of thermowells of three shapes and provides some guidelines for the selection in engineering applications.
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  TheWind Velocity of Longitudinal Air Supply for the Central Smoke Extraction System on Tunnel Fire

  JIANG Xuepeng;LIU Qi

  . 2013, 31(8): 51-56. https://doi.org/10.3981/j.issn.1000-7857.2013.08.007

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  Under the mode of central smoke extraction, in the case of a fire occurs inside the tunnel, jet fans at each end are able to operate and provide supply fresh air. The longitudinal fresh air supply is able to prevent smoke from spreading to the both sides of the tunnel, and control the smoke at the opening smoke extraction vents near the fire. Based on smoke control effectiveness, three evaluation indexes are proposed in order to judge the velocity of longitudinal fresh air supply, they are smoke-exhaust efficiency, smoke spread distance, and the visibility distribution at 2m height of the tunnel. Fire Dynamics Simulation (FDS) is employed to run numerical simulations based on a cross-river sloping tunnel. Twelve groups of fires conditions with -2.8% slopes are simulated. Different opening scheme on smoke extraction vents related to the fire location is taken into account. The smoke extraction vents opening schemes includes three upstream vents/three downstream vents, two upstream vents/four downstream vents, one upstream vent/five downstream vents with the mode of one-way central smoke extraction. And different velocities of longitudinal fresh air supply have been considered as well, which are 0 m/s, 1 m/s, 2 m/s, and 3m/s, respectively. The results of the simulation indicate that the reasonable velocity of longitudinal fresh air supply with central smoke extraction mode is 2.0m/s, which is smaller than the critical wind velocity with the same fire condition. Thus, the conclusion is able to help the smoke extraction system to operate effectively and safely.
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  Applications of Modified Empennage Residual Error GM(1,1) Model in the Prediction of Million Tons Death Rate of Coal Mine

  WANG Liguan;PEI Anlei

  . 2013, 31(8): 57-61. https://doi.org/10.3981/j.issn.1000-7857.2013.08.008

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  Coal mine safety is the top priority of the current production safety work, in order to master the mine safety production status in China, decrease the accident loss, and ensure a healthy, rapid, and sustainable development of China's coal industry, a modified empennage residual error GM (1, 1) model is built on the basis of the traditional GM (1,1) model to analyze the Death Rate Per Million Ton (DRPMT) of coal mines from the year of 2001 to 2011, and to predict the DRPMT of coal mines in the year of 2012 and 2013, respectively. The result shows that the accuracy of traditional GM (1, 1) model is quite poor with the maximum error of 14.35%. Compared with the result given by traditional GM (1, 1) model, the proposed method is easy to operate with reliable results. The average relative error is 1.14% and the maximum relative error is 3.81%, which are all better than that by using the GM (1, 1) model. The method provides the theory guidance for governments and mining enterprises to set safe production targets and policies, establish scientific and efficient security management mechanism. And the method has the great application value in practice.
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  Characteristics of [Cu(Gly-Gly)(Im)]·2H₂O with Its Crystal structure Synthesis and Thermochemical

  ZHAO Yanru;WANG Hongsheng

  . 2013, 31(8): 62-66. https://doi.org/10.3981/j.issn.1000-7857.2013.08.009

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  Complex [Cu(Gly-Gly)(Im)]·2H₂O(s) was prepared by mixing the solution of copper sulfate pentahydrate, glycylglycine and imidazole. The crystal structure of [Cu(Gly-Gly)(Im)]·2H₂O was determined by X-Ray single crystal diffraction. The crystal belongs monoclinic with space group P2₁/n and unit-cell parameters are a=1.0213(6)nm, b=0.7023(4)nm, c=1.5911(9)nm, β=102.393(9)°, V=1.1147(11)nm³, and Z=4, respectively. The dissolution enthalpies of CuSO₄·5H₂O(s)+Gly-Gly(s)+Na₂SO₄(s), Im(s) and [Cu(Gly-Gly) (Im)]·2H₂O(s), 2NaHSO₄·H₂O(s) have been determined in 2mol/L HCl solution by the classical solution calorimetry. According to Hess law, a thermochemical cycle is designed. By calculation, the reaction enthalpy of CuSO₄·5H₂O(s)+Gly-Gly(s)+Im(s)+Na₂SO₄(s)=[Cu(Gly-Gly)(Im)]·2H₂O(s)+2Na·HSO₄·H₂O(s)+H₂O(l) is calculated, Δ_rH_m^θ(298.15K)=(36.763,4±1.132,5)kJ/mol, and furthermore the standard formation enthalpy of [Cu(Gly-Gly)(Im)]·2H₂O(s) has also been calculated, Δ_rH_m^θ{[Cu(Gly-Gly)(Im)]·2H₂O(s), 298.15K}=(-1,770.3±1.4)kJ/mol.
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  Elaborating Carbon Nanotubes Functionalization in the View of Reaction Characteristics of Aromatic C—C Double Bonds

  PENG Zhiguang;YIN Donghong;LIU Jianfu;YU Jingang

  . 2013, 31(8): 67-71. https://doi.org/10.3981/j.issn.1000-7857.2013.08.010

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  Functionalization of nano materials consists of one of the important parts for modern nanometer technology. As a member of the nanomaterials, carbon nanotubes are not soluble/ dispersive in any solbent. In order to improve the dispersion/solubility performance of carbon nanotubes, usually chemical functionalization is the most effective way. The aromatic C—C bonds are the main groups that could be modified. For guiding the functionalization of carbon nanotubes and for pre-determining morphology changes and electronic performances transformation during the functionalization procedure, the theory of aromatic C—C bond reactions in organic chemistry should be well utilized. The results obtaining from carbon nanotubes modification could promote the comprehension for the reaction characteristics of C—C double bonds of the insoluble compounds. Based on the scientific research result in recent years, the effects of different functionalization methods on carbon nanotubes' morphologies and structures are discussed from a structure-performance view. C—C double bond of carbon nanotubes could carry out addition reactions, keeping their original morphologies; therefore the functionalized carbon nanotubes are able to find their wider applications.
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  Progress and Prospect in on the Buried Pipeline Steel with Disbonded Coating

  ZHAO Bo;DU Cuiwei;LI Xiaogang;LIU Zhiyong;CHEN Xu;LI Yueqiang

  . 2013, 31(8): 72-79. https://doi.org/10.3981/j.issn.1000-7857.2013.08.011

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  Pipeline steel holds an irreplaceable position in the modern long distance industry, it is most commonly used in the transportation involving petroleum, gas, coal, and building materials slurry. Most of modern pipeline steel is taken coating as the outer anti-corrosion measures, inevitable resulting in disbonded areas due to external force during the process of buried installation and use. With the electrolyte infiltration and long-term chemical and electrochemical evolution, it forms a special corrosion system in the disbonded area, which could shorten the service life of the pipeline steel quickly, and causing a great potential hazard to industrial production and people's daily life. Therefore, the corrosion of pipeline steel with the disbonded coating has the highest priority and becomes a cutting-edge research topic of the scholars in the corrosion filed at home and aboard. A summary on disbonded system with domestic and foreign research is made from the aspects of research model, classical theory, impact factors, and research progress in recent years. Based on the insufficient result of existing research, the prospect for the future work is investigated.