Creep Characteristics And Creep Model Of Coals With Different Coal Structures

Previous studies have shown that the delayed outburst of coal and gas is related to the creep characteristics of coal.Previous research results have also obtained the influence of gas pressure,confining pressure and axial pressure on the creep properties of gas-bearing coal.A creep constitutive model suitable for describing outburst coal seam is proposed,which lays a foundation for revealing the mechanism of delayed outburst of coal and gas by creep theory.However,previous research results often focus on the creep properties of coal with single coal body structure,ignoring the creep properties of coal body structure.Therefore,this paper takes the outburst coal seam of Qinan Coal Mine in Anhui Province as the research object.Firstly,uniaxial creep tests of different coal body structures are carried out to study the creep characteristic curves of different coal body structures and different loads,and the creep properties are analyzed.On this basis,a creep model describing the non-linear viscous-elastic-plastic properties of coal with different coal body structures is established by combining the non-linear viscous and plastic elements and connecting them with the traditional Burges model in series,and the relevant parameters in the equation are fitted.Finally,the constitutive model is embedded in FLAC3 D numerical calculation software with C++ language to realize the numerical calculation function.The research results can provide a reference for revealing the delayed outburst mechanism of coal and gas from the creep angle of coal structure.The achievements are as follows:1)The different coal samples collected in the field were made into soft coal,soft-hard combination and coal samples with gangue in the middle of soft coal,and the uniaxial creep test was carried out.The research shows that the creep test curves of coal with different coal body structure are basically the same,and a unified creep constitutive model can be established to describe the creep characteristics of coal with different coal body structure;but the creep strength of soft-hard combination and gangue-containing coal is larger than that of soft coal,which is more advantageous to prevent delayed outburst of coal and gas.2)The classical Newtonian body is improved,and a new mechanical element is introduced to describe the accelerated creep stage,which is combined in series with the traditional Burgers model to establish a constitutive model that can fully represent the creep characteristics of coal with different coal body structures.The parameters of the creep model are regressed and identified by Origin 2017 software,and the creep parameters of the new constitutive model are obtained.The correctness of the model is verified by comparing the experimental data curve with the fitting curve.3)Based on the secondary development platform of FLAC3 D software,a new creep model is developed by using C++ language in Visual Studio 2005 environment.A series of simulation examples about creep test are designed to verify the accuracy of the model development.The basic steps and program codes for developing the constitutive model in FLAC3 D are given,which will be similar for other users in the future.The modification of the structural model provides a reference and basis for reference.On this basis,the variation of model parameters and test size on creep is discussed.Figure [55] table [19] reference [60]...