Stress-strain-acoustic responses in failure process of coal rock with different height to diameter ratios under uniaxial compression

不同高径比煤岩单轴压缩破坏过程的应力-应变-声发射响应

Residual coal pillars play an important role in mining the adjacent coal seam safely,managing the gobs and maintaining the stability of abandoned coal mines.The height to diameter ratio(H/D)affects the stability of residual coal pillars.In this study,uniaxial compressive tests of coal specimens with five H/D(2.0,1.5,1.0,0.8 and 0.6)were performed,and the stress,strain and acoustic emission(AE)were monitored.Results show that the uniaxial compressive strength(UCS)and peak strain increase with H/D decreasing.An empirical equation is proposed to calculate the UCS based on the H/D.The AE activities during coal failure process can be separated into four periods.The span of quiet period and rapid decline period shorten with H/D decreasing.The smaller the H/D is,the more complicated the failure characteristics of coal will be.The failure form of coal with H/D of 2.0,1.5,and 1.0 is primarily shear failure,while splitting failure along the axial direction is the mainly mode when H/D is 0.8 or 0.6.The initiation,expansion,aggregation and connection of micro-cracks can be reflected by the real-time spatial evolution of AE event points.

遗留煤柱在相邻煤层安全开采、采空区管理和维护废弃矿井稳定性等方面发挥着重要作用。高径比影响着遗留煤柱的稳定性。本文对5种高径比(2.0,1.5,1.0,0.8和0.6)的煤样进行了单轴压缩试验,并对应力、应变和声发射进行了监测。结果表明,随着高径比的减小,煤样的单轴抗压强度和峰值应变均增大。提出了一个用以描述单轴抗压强度和高径比关系的经验方程。煤样破坏过程中的声发射活动可被划分为四个时期,静默期和快速衰弱期的时长与高径比呈正相关。高径比越小,煤样的破坏特征越复杂,当高径比为2.0,1.5,1.0时,破坏形式以剪切破坏为主,而当高径比为0.8,0.6时,破坏形式以轴向劈裂破坏为主。声发射事件点的实时空间演化可以反映微裂隙的萌生、扩展、聚集和联通。