基于循环加卸载的煤岩体破坏力学行为和能量演化规律研究

doi:10.13722/j.cnki.jrme.2023.1082

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摘要近距离煤层群开采过程中，多重采动会产生显著的循环加卸载效应，为研究循环应力下煤柱及围岩稳定性，结合声发射信号监测，开展煤岩单体和煤岩组合体的单轴循环加卸载试验和PFC3D数值模拟计算。研究结果表明：循环加卸载下，试件应力–应变曲线会呈现出“疏–密–疏”的特征，结合声发射计数和裂纹衍生数目，其变形过程可分为孔隙裂隙压密阶段、弹性变形和裂纹稳定发展阶段、裂纹非稳定发展阶段；循环载荷对组合体中低强度的煤具有强化作用，但会弱化岩石本身强度，试验中不同组合体的平均弹性模量相较单体煤提升了7.03%～18.95%，较单体岩石减弱了0.48%～6.76%，强化/弱化作用与形成组合体的单体试件强度差异呈正相关；循环加卸载过程中，试件裂纹萌生速率和裂纹数目与其强度和变形特性有关，脆性岩体试件的裂纹发育主要集中在裂纹非稳定发展阶段，且试件强度越高，裂纹非稳定发展阶段越集中，而塑性岩体试件的裂纹发育在整个循环加卸载过程均处于一个较为活跃状态；煤、岩单体试件在循环加卸载试验下的破坏模式以压–剪破坏为主，呈单斜面剪切破坏裂纹，而煤岩组合体失稳破坏时，煤体端部先形成柱状劈裂或斜面剪切破坏，破坏面延伸至煤–岩交界面发生偏转，延伸向组合体边界，且偏转角度随组合体中岩石强度增加而增大；循环加卸载试验中，试件的弹性能和耗散能均呈现出增加趋势，单次循环过程中产生的弹性能和耗散能与其自身强度特性呈现负相关，但循环累计产生的弹性能和耗散能与试件自身强度呈正相关。研究结果表明，改变顶底板围岩强度、煤柱与围岩的胶结性可提高循环采动应力扰动下煤柱的承载能力。

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	赵国贞1
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关键词 ：岩石力学, 循环加卸载, 煤&ndash, 岩组合体, 声发射, 裂纹扩展, 能量演化

Abstract：In the process of close-distance seam group mining，multiple mining will cause significant cyclic loading and unloading effects. In order to study the stability of coal pillar and surrounding rock under cyclic stress，uniaxial cyclic loading and unloading tests of coal or rock single body and coal-rock combination combined with acoustic emission signal monitoring and PFC3D numerical simulation calculation were carried out. The results show that，under cyclic loading and unloading，the stress-strain curve of the specimen presents the characteristics of “thinning- dense-thinning”. Combined with the acoustic emission count and the number of cracks derived，the deformation process can be divided into the pore and fracture compaction stage，the elastic deformation and crack stable development stage，and the crack unstable development stage. Cyclic load can strengthen the strength of coal，but weaken the strength of rock. In the test，the average elastic modulus of different compositions increases by 7.03% to 18.95% compared with that of single coal，and decreases by 0.48% to 6.76% compared with that of single rock. The strengthening effect for coal or weakening effect for rock is positively correlated with the strength difference between the single specimens that forming the combination. In the process of cyclic loading and unloading，the crack initiation rate and crack number of specimens are related to their strength and deformation characteristics. The crack development of brittle rock specimens is mainly concentrated in the stage of crack unstable development，and the higher the strength of specimens，the more concentrated the stage of crack unstable development，while the crack development of plastic rock specimens is in a relatively active state during the whole process of cyclic loading and unloading. The fracture pattern of coal and rock single body specimens under cyclic loading and unloading test is mainly compression-shear failure，showing a single inclined plane shear failure crack. When the coal-rock combination fails，the end of the coal body first forms columnar splitting or inclined plane shear failure，the fracture surface is deflected when extends to the coal-rock interface，and extending to the combination boundary. The deflection angle increases with the increase of rock strength in the combination. In the cyclic loading and unloading test，both the elastic energy and dissipative energy of the specimen showed an increasing trend，and the elastic energy and dissipative energy generated in a single cycle were negatively correlated with their own strength characteristics，but the elastic energy and dissipative energy generated in the cyclic accumulation were positively correlated with the specimen's own strength. According to the research results，it is beneficial to improve the supporting capacity of coal pillar under the disturbance of cyclic mining stress to change the strength of surrounding rock and the cementation between coal pillar and surrounding rock.

Key words： rock mechanics cyclic loading and unloading coal-rock combination acoustic emission crack propagation energy evolution

引用本文:

赵国贞1，2，程伟1，刘超1，梁卫国1，2. 基于循环加卸载的煤岩体破坏力学行为和能量演化规律研究[J]. 岩石力学与工程学报, 2024, 43(7): 1636-1645.
ZHAO Guozhen1，2，CHENG Wei1，LIU Chao1，LIANG Weiguo1，2. Failure mechanical behavior and energy evolution of coal and rock under cyclic loading and unloading. , 2024, 43(7): 1636-1645.

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http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2023.1082 或 http://rockmech.whrsm.ac.cn/CN/Y2024/V43/I7/1636

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