煤–过渡层–岩组合体物理力学特征试验及数值模拟研究

Experimental and numerical simulation study on mechanical properties of coaltransition layer-rock composite structures

深部煤系地层中,漫长成岩过程使得部分煤层与岩层之间存在一个岩性过渡区,过渡区与上下岩层、煤层共同组成了一个组合结构。为研究过渡层高度对煤岩组合体变坏特征的影响,首先提出煤、岩石及过渡层3种人工材料的配比设计及煤–过渡层–岩(CFR)组合体试样的制作方案。在此基础上,开展不同过渡层高度的人工CFR组合试样的单轴压缩试验。基于离散元数值模拟软件PFC,采用刚性簇和球颗粒分别表示过渡层中的煤和岩石颗粒,通过其比例变化构建一种过渡层和CFR组合结构PFC表征模型。结合试验结果,对模型参数进行标定并验证算法的有效性。试验与数值模拟结果表明:随着过渡层高度增加,试样强度、峰前耗散能和声发射b值呈现先降低后增加的趋势,弹性应变能呈现逐渐增加的趋势。数值模拟的微裂隙角度分布范围也随着高度增加先缩小后增大,微裂纹萌生区域逐渐由煤层转移到过渡层,声发射定位则逐渐集中至煤与过渡层界面处。研究结果表明过渡层的存在显著改变了煤岩组合结构的物理力学特性。

Within deep coal-bearing strata,a prolonged diagenesis process leads to the existence of a lithological transition zone between some coal and rock layers.This transition zone,together with the adjacent rock and coal layers,constitutes a composite structure.To study the influence of the transition layer's height on the deterioration characteristics of the coal-rock composite,a proportionate design of coal,rock,and transition layer artificial materials,as well as a production plan for coal-transition layer-rock(CFR)composite specimens,were initially proposed.On this basis,uniaxial compression tests of artificial CFR composite specimens with varying transition layer heights were conducted.In addition,based on the discrete element numerical simulation software PFC,rigid clusters and spherical particles were used to represent coal and rock particles in the transition layer.Through their proportion changes,a PFC characterization model for the transition layer and CFR composite structure was constructed.Combined with the test results,the model parameters were calibrated,and the algorithm¢s effectiveness was validated.Both experimental and numerical simulation results indicate that as the height of the transition layer increases,specimen strength,pre-peak dissipated energy,and acoustic emission b initially decrease then increase,while the elastic strain energy shows a progressively increasing trend.The distribution range of numerical simulation micro-fracture angles also initially narrows then expands with increasing height,and the micro-crack initiation area gradually shifts from the coal layer to the transition layer,with the acoustic emission location progressively concentrating on the interface between the coal and transition layer.These results demonstrate that the presence of the transition layer significantly alters the physical and mechanical properties of the coal-rock composite structure.