【作者】 王登科；

【导师】 尹光志；

【作者基本信息】 重庆大学 ， 采矿工程， 2009， 博士

【摘要】 我国是世界上煤与瓦斯突出最严重的国家之一。近年来,随着开采深度的增加、瓦斯压力的增大和开采条件的日趋复杂,煤与瓦斯突出发生的强度及造成的伤亡不断增长,煤与瓦斯突出的预测和防治工作形势十分严峻。煤与瓦斯突出机理的综合作用假说表明,煤与瓦斯突出是地应力、瓦斯压力和煤岩的物理力学性质三者的综合作用结果。在煤与瓦斯突出过程中,主要是含瓦斯煤岩的力学性质、蠕变特性以及渗透特性对突出的发生和发展在起作用。因此研究与这些内容相关的含瓦斯煤岩的本构模型及破坏准则,对进一步揭示煤与瓦斯突出机理和防治煤与瓦斯突出有着十分重要的作用。本文基于前人的研究成果,利用实验研究、理论分析和数值模拟相结合的方法,旨在建立符合含瓦斯煤岩特性的本构模型和失稳准则,并利用实验结果对之进行验证。本文的主要研究成果如下:①利用自主研制的含瓦斯煤岩三轴蠕变瓦斯渗透装置与材料试验机组成的实验系统,对含瓦斯煤岩的力学性质、蠕变特性和渗透特性进行了系统深入的实验研究。在含瓦斯煤岩力学性质的实验研究中,分析了围压和瓦斯压力对含瓦斯煤岩变形特性和抗压强度的影响,得出了相关规律;分析总结出了含瓦斯煤岩三轴压缩下的破坏形式。在含瓦斯煤岩蠕变特性的实验研究中,根据实验结果总结出了含瓦斯煤岩蠕变规律;详细分析了含瓦斯煤岩衰减蠕变阶段和稳态蠕变阶段的蠕变变形和蠕变速率,得到了偏斜应力、围压和瓦斯压力三者对蠕变速率的影响规律;分析总结出了含瓦斯煤岩加速蠕变阶段的启动条件及该阶段的蠕变速率特征。在含瓦斯煤岩渗透特性的实验研究中,根据实验结果总结出了围压和瓦斯压力对含瓦斯煤岩渗透率的影响规律,分析了Klinkenberg效应和应力-应变全过程对含瓦斯煤岩渗透率影响,并得出了一些有价值的分析结果。②基于实验结果,利用模型辨识方法得到了描述含瓦斯煤岩粘弹性流变特性的最适合流变模型为伯格斯体;提出了一种能反映含瓦斯煤岩加速蠕变的改进的粘弹塑性模型,将之与伯格斯体一起组成了一维含瓦斯煤岩的非线性粘弹塑性流变模型,进而推导得出了含瓦斯煤岩三维非线性粘弹塑性流变模型,并利用实验结果进行了验证;利用常微分解的稳定性理论,对含瓦斯煤岩非线性粘弹塑性流变模型进行了稳定性分析,得到了含瓦斯煤岩的流变失稳条件。③在不可逆热力学框架内,利用连续介质损伤力学方法建立了用以描述含瓦斯煤岩的弹塑性变形、瓦斯吸附效应、体积膨胀、围压敏感、弹性模量的退化、各向异性损伤、应变强化及软化、非关联塑性流动等物理现象及力学行为的弹塑性耦合损伤本构模型,并对之进行了实验验证。④在多孔介质有效应力原理中引入了煤岩吸附瓦斯的膨胀应力,建立了含瓦斯煤岩的固气耦合动态模型,该模型不但考虑了含瓦斯煤岩在变形过程中孔隙度和渗透率的动态变化特征,而且还反映了瓦斯气体可压缩性和煤岩骨架可变形的特点,从而更真实全面地反映了含瓦斯煤岩的固气耦合效应;利用COMSOL-Multiphysics有限元软件根据所提出的含瓦斯煤岩的固气耦合本构模型建立了有限元模型,得到了含瓦斯煤岩固气耦合动态模型的数值解,同时还分析了Klinkenberg效应对含瓦斯煤岩渗透率的影响。⑤利用初等突变理论建立了基于试验机-试样分析系统的含瓦斯煤岩蠕变破坏的尖点突变失稳模型,得出三轴压缩条件下含瓦斯煤岩蠕变失稳破坏条件。⑥在总结国内外关于岩石类材料的强度准则及实验结果基础上,提出了一种符合含瓦斯煤岩三轴应力条件下变形的强度判据,该判据不但能描述三轴压缩下中间主应力的影响及含瓦斯煤岩非线性应变强化特征,而且还可以描述含瓦斯煤岩的拉伸破坏。更多还原

【Abstract】 Our country is one of the most serious coal and gas outburst countries in the world. In the recent years, the intensity of coal and gas outburst and the fatalities caused by the outburst are growing with the increasing of mining depth, pressure of gas and complexity of mining condition, and the work of forecasting, preventing and controlling coal and gas outburst is very severe urgent. The comprehensive effect hypothesis shows that coal and gas outburst is caused by the comprehensive effect of ground stress, gas pressure and the physical and mechanical properties of coal. In the course of a coal and gas outburst, mechanical properties, creep characteristics and seepage characteristics of gas-saturated coal are the main factors which control the occurring and development of the outburst. Therefore, research on constitutive model and failure criterion of gas-saturated coal is very important for further revealing the mechanism of coal and gas outburst and preventing and controlling the outburst. Based on the research results of predecessors, applying experimental study, theory analysis and numerical simulation, the goal of this paper is establishing constitutive models and failure criterions of gas-saturated coal and validating them by using testing data.The main research results obtained in this paper are as follows:①By using of a testing system which is made up of a self-made triaxial gas-seepage device and a servo-controlled testing machine, mechanical properties, creep characteristics and seepage characteristics of gas-saturated coal were systematically studied in laboratory. In experimental study of mechanical properties of gas-saturated coal, the effects of both confining pressure and gas pressure on deformation characteristics and compressive strength were analyzed, and related rules were summarized. At the same time, the failure mode of gas-saturated coal under triaxial compression was also derived. In experimental study of creep characteristics of gas-saturated coal, the universal law of creep deformation of gas-saturated coal was summarized bases on testing results. In addition, the creep deformation and creep rate of attenuating and steady-state creep stages were analyzed in detail, the rules of effects of deviatoric stress, confining pressure and gas pressure on creep rate were obtained. Moreover, the start condition and creep rate characteristics of accelerating creep stage were also educed. In experimental study of seepage characteristics of gas-saturated coal, in according to the testing data, the effect rules of confining pressure and gas pressure on permeability of gas-saturated coal were worked out, as well as the Klinkenberg effect and the effect of complete stress-strain curve were analyzed simultaneously, and some valuable analysis results were found out.②On the basis of testing data, by means of model indentification method, Burgers body is considered as the optimum rheological model for describing the visco-elastic rheological properties of gas-saturated coal. In the meanwhile, a modified visco-elastic-plastic model was proposed for depicting the creep deformation of accelerating creep stage. The one-dimensional nonlinear visco-elastic-plastic rheological model for gas-saturated coal was built by connecting the modified model with a Burgers body in parallel, and then the three-dimensional nonlinear visco-elastic-plastic rheological model for gas-saturated coal was derived. The three-dimensional rheological model for gas-saturated coal was verified by using testing data finally. Besides these, the stability analysis of the three-dimensional rheological model of gas-saturated coal was carried out, and the rheological failure condition of gas-saturated coal was obtained.③In irreversible thermodynamics framework, a coupled elastoplastic damage constitutive model for gas-saturated coal was established according to the continuum damage mechanics method. The constitutive model can effective describe many physical phenomena and mechanical behavior of gas-saturated coal, such as elastoplastic deformation, gas adsorption effect, volume expansion, confining pressure sensitivity, degeneration of elastic modulus, anisotropic damage, strain hardening and softening, non-associated plastic flow, and so on. Furthermore, the constitutive model was verified in terms of testing results.④A solid-gas coupling dynamic model for gas-saturated coal was proposed by introducing the swell stress of gas adsorption into the effective stress principle of porous. The dynamic model can more truly and completely reflect the coupling effect between solid and gas in gas-saturated coal than previous similar models developed because not only the dynamic change property of porosity and permeability of gas-saturated coal but also the gas compressibility and the skeleton deformability of gas-saturated coal were taken into account in this model. A finite element model related to the solid-gas coupling dynamic model of gas-saturated coal was constructed by using COMSOL-Multiphyics software, and then the numerical results was yielded. In addition, the Klinkenberg effect was also discussed by means of numerical simulation method.⑤Based on the analysis system of testing machine and specimen, a cusp catastrophe instability model for creep failure of gas-saturated coal was built in terms of elementary catastrophe theory, and then the creep instability condition of gas-saturated coal under triaxial compression was obtained.⑥A strength criterion for gas-saturated coal was proposed in according to the summarization of strength criterions of rock-like material at home and abroad and experimental results. This strength criterion can describe not only the intermediate principle stress effect and the nonlinear strain hardening of gas-saturated coal under triaxial compression but also the tensile failure characteristics.更多还原