基于变形场时空演化的煤冲击劈裂试验研究

采用霍普金森杆冲击加载装置,通过高速摄影机搭建实验的数据采集系统,以数字散斑相关方法作为实验的观测手段,对巴西圆盘煤试件在冲击载荷作用下的冲击劈裂变形场演化规律及裂隙扩展特征进行实验研究。试验结果表明:1从变形场演化特征分析,加载初期变形场相对均匀,随荷载增加变形局部化特征明显。变形场时空演化总体表现为两个阶段特征:峰前水平方向变形量值变化较快,垂直方向变形量值变化较慢;峰后由于裂隙演化,水平方向变形量值变化缓慢,垂直方向变形量值变化较快;2霍普金森杆加载过程中,在试件两端加载处出现了局部压碎区,加载过程中主裂纹从压碎区域萌生并沿径向加载方向扩展至另一端贯通破坏;3实验测得煤样在冲击载荷作用下峰前应力随应变呈线性增长,弹性模量与静荷载相比有较大提高,由于压碎区域存在,冲击加载实验得到的煤试件拉伸强度与实际相比偏小。

Experimental study on coal impact fracturing based on temporal and spatial evolution of deformation field

The evolution characteristics of deformation fields and displace fields of the deformation localization are investigated and analyzed by using the digital speckle correlation method.The test material is a kind of coal and the specimens are loaded by Hopkinson bar impact loading device.Experimental data are collected with high-speed camera.The analysis results show that：① The initial deformation field is relatively uniform,and the characteristic of deformation localization is obvious with the increase of load.The temporal and spatial evolution of the deformation field is characterized as two stages：before the stress peak,the horizontal deformation value develops rapidly and the vertical deformation value develops slowly；due to the evolution of fracture,after the stress peak,the horizontal deformation value develops slowly and the vertical deformation value develops rapidly.② In the loading process of Hopkinson bar,at both ends of the test piece,the local crushing zone appears.During the loading process,the main crack is initiated from the crushed zone and extended to the other end through the radial loading direction.③ The experimental results show that the stress of coal sample under the impact load increases linearly with the strain.Compared with static load,the elastic modulus is greatly improved.Due to the presence of the crushed zone,the strength of coal samples with impact loading test is relatively small compared with the actual results.