两向加卸载含瓦斯煤变形破裂数值模拟研究
Numerical Simulation Research on Deformation and Fracture of Coal Containing Gas Under Axial Loading and Lateral Unloading Condition
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摘要: 为了模拟煤矿工作面前方应力变化时含瓦斯煤体的力学特性，应用RFPA2D-Flow软件模拟研究了轴向加载-横向卸载作用下含瓦斯煤的变形破裂规律，讨论了初始围压、轴压和卸载速率效应对试样变形破坏的影响。研究结果表明：在加载和卸载方向，轴向应力和横向应力初期都呈线性增加，当达到极限强度后煤体的变形破裂导致急剧的应力降，直至煤样失去承载能力时基本保持恒定。初始围压、轴压越大，卸载速率越小，煤体的极限抗压、拉强度及其对应的轴向、横向应变越大；峰值强度及应变与初始围压、轴压呈明显的线性相关性，而与卸载速率表现出阶梯状，随着卸载速率的增加极限强度及应变减小速率逐渐降低。Abstract: In order to simulate the mechanical properties of coal containing gas under the condition of in-situ stress variation in front of working face, RFPA2D-Flow software is used in this paper to study the law of deformation, fracture process of coal containing gas under axial loading and lateral unloading of biaxial loading, and we discuss the effect of initial confining pressure, initial axial pressure and unloading rate on the deformation and failure of the specimen. The research results show that: in the direction of loading and unloading, the axial stress and the transverse stress increase linearly in the initial stage; when the stress reaches to the ultimate strength of the coal, the deformation and fracture of the coal will lead to a sharp stress drop, until the coal sample loses its bearing capacity; the greater the initial confining pressure and axial pressure, the smaller the unloading rate, the greater the ultimate compressive and tensile strength and the strain that coal can bear. The ultimate strength and strain are linearly related to the initial confining pressure and the initial axial pressure, however, the relationship between these mechanical parameters and the unloading rate shows a stepwise shape. With the increase of the loading rate, the ultimate strength and strain reduction rate decrease gradually.
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