| 峰后围压卸载对原煤变形和渗透特性的影响 |
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| 引用本文： | 刘超,张东明,尚德磊,赵宏刚,宋真龙,俞欢.峰后围压卸载对原煤变形和渗透特性的影响[J].岩土力学,2018,39(6):2017-2024. |
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| 作者姓名： | 刘超 张东明 尚德磊 赵宏刚 宋真龙 俞欢 |
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| 作者单位： | 1. 重庆大学 煤矿灾害动力学与控制国家重点实验室，重庆 400030；2. 重庆大学 资源及环境科学学院，重庆 400030； 3. 重庆大学 复杂煤气层瓦斯抽采国家地方联合工程实验室，重庆 400030 |
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| 基金项目： | 国家自然科学基金（No.51434003，No.51374256） |
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| 摘 要： | 运用自主研制的煤岩热-流-固耦合试验系统，以原煤为研究对象，进行峰后轴压保持在不同应力水平下围压的卸载试验，以分析围压卸载对原煤变形特性和渗透特性的影响。研究结果表明：通过径向应变 、轴向应变 和体应变 的不可恢复变形量以及三者在力加载过程中的响应程度来定义损伤变量，满足损伤变量的变化区间0, 1]，并以此计算煤样在卸载过程中的损伤量，得到在峰后轴压 保持不变，对围压 进行卸载时，损伤量D随着 的减小而增大，煤样的损伤程度越来越大；当轴压卸荷到不同应力时，煤样的渗透率随围压卸载次数的增加而增大，表明当 减小时， 对渗透率的影响越来越重要，同时煤样内部的孔隙裂隙以发育、扩展、延伸为主。此外，渗透率k在 卸载初期，几乎不增加；当 继续卸载时， 开始增大，并且斜率越来越大，表明煤样的损伤加剧。当保持 不变，对 进行卸载时，相当于摩尔应力圆半径增大，煤样向破坏的趋势发展，发生二次破坏的可能性增大。随着 的卸载，卸围压前 越大，摩尔应力圆半径越大，煤样的承载能力就越弱，更易发生煤样的二次破坏，表现在煤样的轴向应变 和径向应变 发生突变。
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| 关 键 词： | 围压卸载 损伤 损伤变量表达式 渗透率 摩尔应力圆 二次破坏 |
| 收稿时间： | 2016-10-31 |
Influence of confining pressure unloading at post-peak on deformation and permeability characteristics of raw coal |
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| LIU Chao,ZHANG Dong-ming,SHANG De-lei,ZHAO Hong-gang,SONG Zhen-long,YU Huan.Influence of confining pressure unloading at post-peak on deformation and permeability characteristics of raw coal[J].Rock and Soil Mechanics,2018,39(6):2017-2024. |
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| Authors: | LIU Chao ZHANG Dong-ming SHANG De-lei ZHAO Hong-gang SONG Zhen-long YU Huan |
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| Institution: | 1. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China; 2. College of Resources and Environmental Sciences, Chongqing University, Chongqing 400030, China; 3. State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam, Chongqing 400030, China |
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| Abstract: | In this study, experiments were conducted on raw coal specimens by using the self-developed triaxial servo-controlled seepage equipment for thermo-hydro-mechanical coupling of coal containing methane. Experiments were carried out when the axial pressure maintained at different stress levels but the confining pressure was unloaded. We studied the effects of unloading confining pressure on deformation properties and permeability characteristics of gas-filled coal at the post-peak. The results showed that the damage variable was defined by the unrecoverable deformations of radial strain , axial strain and volumetric strain and the response of these three parameters during the process of unloading. The interval 0, 1] of damage variable was satisfied to calculate the damage quantity of coal specimen in the process of unloading. When the axial pressure remained constant and the confining pressure was unloaded, the amount of damage quantity D increased with the decrease of and the damage degree of coal specimen increased greatly. When unloading the axial pressure to different stress levels, the permeability of coal specimen increased with the growing unloading times of confining pressure. It indicated that the influence of confining pressure on permeability was more and more important when decreased. At the same time, the pores and fractures in the coal specimen were developed, expanded and extended. In addition, the permeability k hardly increased at the beginning of unloading . As continued to unload, k began to increase and the slope became growing, indicating the severe damage of coal specimen. The radius of Mohr stress circle was equivalent to an increase under this stress path of loading and unloading, and coal specimens tended to destruction causing the increasing possibility of the occurrence of secondary failure. At the higher level of , with the unloading of , the radius of Mohr stress circle increased and the supportability of coal specimens became weaker. Hence, the secondary failure easily occurred, which manifested the abrupt change of axial strain and radial strain . |
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| Keywords: | confining pressure unloading damage damage variable expression permeability Mohr stress circle secondary failure |
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