非均质结构对煤岩组合体强度及破坏特征影响的离散元研究

Discrete element study on influence of heterogeneous structure on strength and failure characteristics of coal rock combination

煤柱中赋存的非均质结构往往会影响工作面的安全生产,为研究非均质结构对煤岩组合体强度及破坏演化特征的影响,基于离散元软件,建立了含有随机分布非均质结构的煤岩组合体模型,考虑非均质结构强度为煤体结构的25%、50%、200%和400%,对含非均质结构煤岩组合体的强度特征、裂纹发育扩展过程进行了研究,分析了其影响机理。结果表明:煤岩组合体峰值强度和弹性模量随非均质结构强度的增加而增加,峰值应变和起裂应力随非均质结构与煤体结构强度差的增加而逐渐减小;煤岩组合体应力场受非均质结构分布形态影响,应力集中区往往出现在2类结构中强度较高的区域,并以2类结构交界为边界;在加载过程中,微裂纹首先出现在强度较弱的结构中,并在弱属性结构内部发育扩展;导致试样破坏的贯通裂隙形态取决于弱属性结构的分布特征。

The heterogeneous structure in the coal pillar often affects the safety production of the working face.In order to study the influence of heterogeneous structure on the strength and failure evolution characteristics of coal rock combination,a coal rock combination model with randomly distributed heterogeneous structure is established based on discrete element software.Considering that the strength of heterogeneous structure is 25%,50%,200%and 400%of coal structure,the strength characteristics,crack development and propagation process of coal rock combination with heterogeneous structure are studied,and its influence mechanism is analyzed.The results show that:the peak strength and elastic modulus of coal rock combination increase with the increase of the strength of heterogeneous structure,and the peak strain decreases with the increase of the strength difference between heterogeneous structure and coal structure.The stress field of coal rock combination is affected by the distribution of heterogeneous structure.The stress concentration area often appears in the area with higher strength in the two types of structures,and takes the junction of the two types of structures as the boundary.During the loading process,micro-cracks first appear in the structures with weak strength,and develop and expand inside the structures with weak attributes.The morphology of through-crack leading to sample failure depends on the distribution characteristics of weak attribute structure.