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instability criterion for the system composed of elastic beam and strain-softening pillar based on gradient-dependent plasticity

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Journal of University of Science and Technology Beijing 2005年第1期12卷 1-5页

作者： XuebinWang Dept.ofMechanicsandEngineeringSciences LiaoningTechnicalUniversityFuxin123000China

A mechanical model is proposed for the system of elastic beam and strain-softening pillar where strain localization is initiated at peak shear stress. To obtain the plastic deformation of the pillar due to the shear slips of multiple shear bands, the pillar is divided into several narrow slices where compressive deformation is treated as uniformity. In the light of the compatibility condition of deformation, the total compressive displacement of the pillar is equal to the displacement of the beam in the middle span. An instability criterion is derived analytically based on the energy principle using a known size of localization band according to gradient dependent plasticity. The main advantage of the present model is that the effects of the constitutive parameters of rock and the geometrical size of structure are reflected in the criterion. The condition that the derivative of distributed load with respect to the deflection of the beam in the middle span is less than zero is not only equivalent to, but also even more concise in form than the instability criterion. To study the influences of constitutive parameters and geometrical size on stability, some examples are presented.

关键词： instability criterion elastic beam strain-softening pillar strain localization shear band energy principle

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Elimination mechanism of coal and gas outburst based on geo‑dynamic system with stress–damage–seepage interactions

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International Journal of Coal Science & Technology 2023年第4期10卷 47-61页

作者： Lingjin Xu Chaojun Fan Mingkun Luo Sheng Li Jun Han Xiang Fu Bin Xiao College of Mining Liaoning Technical UniversityFuxin 123000China Energy Business Department Shanxi Lu’an Chemical GroupChangzhi 046200China Resource Department Liaoning Geology Engineering Vocational CollegeDandong 118000China

Coal and gas outburst is a complex dynamic disaster during coal underground mining.Revealing the disaster mechanism is of great signifcance for accurate prediction and prevention of coal and gas outburst.The geo-dynamic system of coal and gas outburst is proposed.The framework of geo-dynamic system is composed of gassy coal mass,geological dynamic environment and mining disturbance.Equations of stress–damage–seepage interaction for gassy coal mass is constructed to resolve the outburst elimination process by gas extraction with boreholes through layer in foor roadway.The results show the occurrence of outburst is divided into the evolution process of gestation,formation,development and termination of geo-dynamic system.The scale range of outburst occurrence is determined,which provides a spatial basis for the prevention and control of outburst.The formation criterion and instability criterion of coal and gas outburst are established.The formation criterion F1 is defned as the scale of the geo-dynamic system,and the instability criterion F2 is defned as the scale of the outburst geo-body.According to the geo-dynamic system,the elimination mechanism of coal and gas outburst—‘unloading+depressurization’is established,and the gas extraction by boreholes through layer in foor roadway for outburst elimination is given.For the research case,when the gas extraction is 120 days,the gas pressure of the coal seam is reduced to below 0.4 MPa,and the outburst danger is eliminated efectively.

关键词： Coal and gas outburst Geo-dynamic system Stress–damage–seepage coupling Elimination mechanism instability criterion Gas extraction

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Web pillar stability in open‑pit highwall mining

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International Journal of Coal Science & Technology 2022年第1期9卷 167-182页

作者： Juyu Jiang Zhuowei Zhang Dong Wang Laigui Wang Xinping Han College of Mines Liaoning Technical UniversityFuxin 123000LiaoningChina

When highwall mining technology is applied to recover large amounts of residual coal left under the highwall of a big openpit mine,a reasonable coal pillar width is required to ensure the stability of the web pillars.Using numerical simulations,this paper studied the characteristics of the abutment stress distribution in the web pillars under different slope angles and mining depths,and established a relation describing the stress distribution in the web pillar.The relationship between the abutment stress and the ultimate strength of the web pillar under different pillar widths was also analyzed.In combination with the failure characteristics of the pillar yield zone,this relationship was used to explore the instability mechanism of web pillars.Finally,the optimal retaining widths of the web pillars were determined.Based on the modeling results,a mechanical bearing model of the web pillar was established and a cusp catastrophe model of pillar-overburden was constructed.Additionally,the web pillar instability criterion was derived.By analyzing the ultimate strength of the web pillars,a formula for calculating the yield zone width either side of the pillars was established.Using the instability criterion of web pillars in highwall mining,a reasonable pillar width can be deduced theoretically,providing significant guidance on the application of highwall mining technology.

关键词： Open-pit mine Highwall mining instability criterion Web pillar Coal pillar width

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Mechanical behaviors analysis of all position MAG weld pool instability

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China Welding 2013年第2期22卷 72-75页

作者：岳建锋李亮玉刘文吉王天琪 Tianjin Key Laboratory of Advanced Mechatronics Equipment Technology Tianjin Polytechnic University Tianjin 300387

All position MAG welding is widely applied in pipeline processing. Whereas, welding defects easily happen when welding current is beyond 200 A. In this paper, the force equilibrium condition and influence mechanism of weld pool instability were discussed. Using the hysteresis tension theory on liquid interface, the radial and tangential force imposing on weld pool was analyzed to obtain the mechanical instability criterion on weld pool formation. The criterion provides a good explanation for those corresponding measures promoting weld pool formation in practice.

关键词： all position MAG welding hysteresis tension instability criterion

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On theoretical research for nonlinear tearing mode

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Plasma Science and Technology 2018年第9期20卷 8-11页

作者：李定杨文蔡辉山 Institute of Physics Chinese Academy of Sciences Beijing 100190 People's Republic of China Department of Modern Physics University of Science and Technology of China Hefei 230026 People's Republic of China University of Chinese Academy of Sciences Beijing 100049 People's Republic of China

The analytical approaches for nonlinear tearing mode have been reviewed.It is shown that Rutherford＇s model has triggered numerous studies on the nonlinear tearing mode.Its physical picture is clear meanwhile its mathematical method is ingenious but still puzzling to understand.It is trying to find how the ＇nonlinear behavior＇ resulted from the linear equation by a nonlinear transform.It is indicated that Li＇s model for the tearing mode includes the linear growth,Rutherford＇s behavior and the new behavior.It was found that the quasilinear modification of magnetic field provided a new damping mechanism for nonlinear growth.The new behavior w~ t1/2 becomes dominant if the mode is weakly unstable.It is shown that many analytical methods have been developed to calculate the criterion parameter D＇ of the tearing mode.Li＇s instability criterion can cover the previous results in the limit cases.

关键词： tearing mode nonlinear evolution instability criterion

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