基于间接拉伸试验的煤岩层理效应研究

Research on coal bedding effect based on indirect tensile test

采用多种先进的宏细观测试手段,探究煤的层理构造和矿物分布。进行加载方向与煤岩层理面平行和垂直的间接拉伸以及实时声发射(AE)试验,分析了煤的破坏机理、拉伸力学特性以及在拉伸过程中声发射时空序列特征和损伤变量演化的层理效应。研究表明:方解石矿物主要沿煤层理面分布,对裂隙的萌生和发展起着关键作用;加载方向平行和垂直于层理面煤岩的抗拉强度分别为0.706和1.039 MPa;平行组试样声发射活动的整体水平弱于垂直组,但平行组试样AE事件在破坏前短期内激增,总能量释放少,破坏突然,主裂纹沿层理面发展,垂直组试样的AE信号在低应力水平出现,AE振铃计数率和能率均强于平行组,空间定位点有明显的成核区域;垂直组和平行组损伤变量D值变化曲线分别呈现出阶梯式和两段式特征,具有明显差异,基于AE能量计算的岩石损伤状态更加符合实际。

By using several advanced macro and micro test methods,the bedding structure and mineral distribution of coal were analyzed,which lay the foundation for the study on the mechanism of coal rock bedding effect.Indirect tensile test and acoustic emission（ AE） test in which loading direction is parallel and perpendicular to the bedding plane of coal were conducted,and the failure mechanism,bedding effect on tensile mechanical properties,as well as the bedding effect on AE timing parameters,law of energy release,spatial evolution characteristics and the damage variable D during the stretching process were analyzed.The results show that,the calcite mineral mainly distributes along the bedding plane and it plays an important role in the process of initiation and development of cracks.The tensile strength of coal whose loading direction is parallel and perpendicular to bedding plane is 0.706 and 1.039 MPa,respectively.Compared with the vertical group,the AE activity of parallel group is weaker in the whole process,and AE events increase sharply in a short time when approaching to failure,the failure occurs suddenly and the main fracture surfaces distrib-ute along the bedding plane.The AE signal of vertical group appears at the beginning of the loading,the AE ring count rate and energy rate are higher than the parallel group and the spatial localization of vertical group has an obvious nucleation area.The damage variable D in the vertical and parallel groups shows an obvious different characteristic with ladder type and two-section type,respectively.The rock damage state based on AE energy is more coincident with reality.