In the western mining area of China, mudstone-clay composite roofs are commonly found in coal seam roadway. This kind of roadway surrounding rock has poor self-stabilization ability and is difficult to support. Therefore, through a series of uniaxial loading and acoustic emission (AE) experiment, this study explores the mechanical properties of mudstone-clay composites (MCCs) considering different thickness, horizon, quantity, and moisture content of clay layers. The research results show that: First, if the clay meets water, the bearing and deformation resistance of the MCCs are significantly weakened. The thicker the clay layer and the more quantity, the smaller uniaxial compressive strength and elastic modulus of MCCs. Second, the AE energy characteristics in different combinations of specimens are disparate. For the MCCs with hydrous clay and thicker mudstone, the AE energy peaks mostly appear at the beginning and end of the stress step in the post-peak stage. Third, the moisture state of the clay layers significantly influences the MCCs' failure mode and crack type. If the clay is exposed to water, the failure mode of MCCs changes from tension-shear joint failure to single tension failure. Finally, the tearing effect of clay lateral displacement on mudstone is dominant to mudstone cracking. The bonding effect of clay prompts the rock blocks on both sides of the mudstone fissures and clay layer form a triangular structure. In the post-peak stage, the periodic instability and rebalance of the triangular structure lead to a stepped decline in the stress-strain curves of the MCCs.

中文翻译：

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单轴压缩泥岩-粘土复合材料力学性能及声发射特性研究

在我国西部矿区煤层巷道中常见泥岩-粘土复合顶板。此类巷道围岩自稳能力差，支护难度大。因此，本研究通过一系列单轴加载和声发射（AE）实验，探讨了考虑不同粘土层厚度、层位、数量和含水量的泥岩-粘土复合材料（MCC）的力学性能。研究结果表明：首先，当粘土遇水时，MCC的承载力和抗变形能力显着减弱。粘土层越厚、数量越多，MCCs的单轴抗压强度和弹性模量越小。其次，不同样本组合的声发射能量特征是不同的。对于含水粘土和较厚泥岩的MCC，AE能量峰值大多出现在峰后阶段应力阶的开始和结束处。第三，粘土层的潮湿状态显着影响MCC的失效模式和裂纹类型。如果粘土暴露在水中，MCCs的破坏模式就会从拉剪联合破坏转变为单一拉破坏。最后，粘土侧向位移对泥岩的撕裂作用对泥岩开裂起主导作用。粘土的粘结作用促使泥岩裂隙两侧的岩块与粘土层形成三角形结构。在峰值后阶段，三角形结构的周期性不稳定和重新平衡导致MCC的应力-应变曲线阶梯式下降。