加卸载路径下含水泥岩力学行为和破坏形态研究  

Study on mechanical behavior and failure mode of water-bearing mudstone under loading and unloading path

作　　者：刘跃东 康红普[1,2] LIU Yuedong;KANG Hongpu(CCTEG Coal MiningResearch Institute,Beijing 100013,China;Coal Mining Branch,China Coal Research Institute,Beijing 100013,China)

机构地区：[1]中煤科工开采研究院有限公司,北京100013 [2]煤炭科学研究总院开采研究分院,北京100013

出　　处：《采矿与安全工程学报》2022年第5期1011-1020,共10页Journal of Mining & Safety Engineering

基　　金：国家重点研发项目(2017YFC0603000);中煤科工开采研究院有限公司青年基金项目(KCYJY-2021-QN-01)。

摘　　要：泥岩巷道在开挖遇水后极易发生变形、垮落,严重影响巷道安全掘进。为揭示含水状态和开挖效应对泥岩巷道影响机理,采用X射线衍射(XRD)和扫描电镜(SEM)对泥岩遇水前后细观结构变化进行定性表征,并采用三轴试验机对5种含水率下的泥岩进行三轴加载和加卸载试验。结果表明:1)富含高岭石的泥岩遇水后,片状结构的高岭石会变为卷曲状的埃洛石,层间间距变大,孔隙率增大,分子作用力减弱,物性劣化造成强度衰减。2)与加载作用相比,同等含水状态卸载作用下泥岩的强度较低,卸载作用导致偏应力的激增,泥岩提前进入屈服段,承载强度较低。3)卸载路径峰后曲线陡峭,泥岩脆性更强,扩容明显,破坏更为剧烈。随着含水率增加,泥岩由脆性向塑性转化,含水状态和应力路径均会影响岩石力学特性。4)对比原始、遇水加卸载破坏形态,泥岩遇水后产生的微裂隙会影响最终破裂形态,在卸载路径中更为明显,张拉破坏所占比例更高。针对卸载路径下含水泥岩破坏时机提前,现场应及时加强支护以恢复围压,减少含水巷道破坏风险。Mudstone roadway is prone to deform and collapse after excavation with water,which seriously affects the safety of roadway excavation.To reveal the mechanism of the water-bearing state and excavating effect on mudstone roadway,X-ray diffraction(XRD)and scanning electron microscopy(SEM)was used to qualitatively characterize the physical properties of mudstone and the microscopic structures before and after water absorption.The triaxial loading and unloading tests of mudstone under five water contents were carried out by using the triaxial test machine.The results show that:1)After the mudstone rich in kaolinite absorbing water,the sheet structure of kaolinite will change to curled halloysite,with a larger interlayer spacing,an increasing porosity,weakened molecular force,attenuated strength caused by the physical degradation.2)Compared with the loads,the unloads cause a lower mudstone strength when having the same water-bearing level.The unloading effect leads to a significant increase in deviatoric stress,the mudstone enters the yielding stage in advance with lower peak strength.3)Compared with the full stress-strain curve,at the same water-bearing level,the post-peak curve of the unloading path of mudstone is steeper,representing a higher brittleness,an obvious dilatancy and a more severe failure.Also,with increasing water content,the mudstone transforms from brittleness to plasticity.It indicates that the mechanical properties of mudstone are affected by the water-bearing level and stress path.(4)Compared with the original,water-bearing,loading and unloading failure mode,the final fracture morphology of mudstone is affected by the micro-cracks under water conditions,which can be more obvious in the unloading path,and the proportion of tensile failure is higher.Given the early failure of water-bearing mudstone under the unloading path,the support should be strengthened in time to restore the confining pressure and reduce the failure risk of the water-bearing roadway.

关 键 词：加卸载作用 含水状态 泥岩 力学特性 破坏形态 

分 类 号：TD315[矿业工程—矿井建设]