摘要
选用煤层三个不同方向煤样,对比单轴加载前后煤样超声实验和核磁共振(NMR)实验,研究煤孔、裂隙结构应力变形各向异性特征及其对声学参数的影响.结果表明:未加载时,平行层理方向纵波波速、品质因子是垂直层理方向的近2倍;单轴加载过程中各向异性先减后增.T_2谱弛豫特征,平行层理的面割理方向和端割理方向分别显示为双峰和三峰,垂直层理方向以单峰为主.单轴加载后,经历弹性变形煤样T_2弛豫强度减小,塑性变形煤样T_2弛豫形态改变.理论分析得出,压密、弹性阶段煤孔、裂隙密度减小导致波速增加,衰减减小;塑性变形阶段孔、裂隙密度减小和裂隙尺寸的增加共同作用导致波速稳定,衰减增大.因此,可采用超声技术与核磁共振技术结合方法,研究煤岩体应力变形各向异性特征,这对地球物理技术应用于煤微观结构研究具有重要意义.
The purpose of this paper is to study the influence of stress and deformation anisotropy of coal pores and fractures on ultrasonic parameters.Coal samples of three different directions were used to compare the ultrasonic and Nuclear Magnetic Resonance (NMR)experiments before and after uniaxial loading.The results show that,when unloaded,the velocity and quality factor of P-wave in the direction of parallel bedding are nearly 2 times of the vertical bedding direction.The anisotropy decreases first and then increase during the uniaxial loading.The characteristics of T2 spectrum indicate that,the direction of parallel-bedding and vertical-face cleat and vertical-butt cleat samples are shown as two peaks and three peaks respectively,however the direction of vertical-bedding samples are dominated by single peak.After uniaxial loading,the T2 relaxation strength of coal samples decreases with elastic deformation and changes with plastic deformation.Theoretical analysis states that the reduction of'the density of coal pores and fractures in the compacted and elastic phase leads to an increase in the wave velocity and a decrease in attenuation however changes of the fractures in the plastic phase result in a stable wave velocity and an increase in attenuation.Therefore,the combination of ultrasonic technology and nuclear magnetic resonance technology can be used to study the anisotropic characteristics of stress and deformation in coal rock mass,which is of great significance for the application of geophysical techniques to the study of coal microstructure.
作者
卢方超
高建良
张玉贵
刘佳佳
LU Fang-chao;GAO Jian-liang;ZHANG Yu-gui;LIU Jia-jia(School of Safety Sctence and Engineering,Henan Polytechnic University,Henan Jiaozuo 454000,China;State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Henan Polytechnic University,Henan Jiaozuo 454000,China;Coal Production Safety Collaborative Innovation Center in Henan Province,Henan Jiaozuo 454000,China)
出处
《地球物理学进展》
CSCD
北大核心
2018年第6期2555-2562,共8页
Progress in Geophysics
基金
国家自然科学基金(51734007
51604101
51704099)
河南理工大学博士基金(B2018-59)
河南省瓦斯地质与瓦斯治理重点实验室-省部共建国家重点实验室培育基地开放基金项目(WS2017B06)和深井瓦斯抽采与围岩控制技术国家地方联合工程实验室开放基金资助项目(G201608)联合资助
关键词
单轴加载
孔、裂隙
各向异性
声波特征
核磁共振特征
uniaxial loading
pores and fractures
anisotropy
ultrasonic characteristics
Nuclear Magnetic Resonance (NMR)
