Characteristics of borehole surface deformation and fracture evolution in progressively demaged coal samples containing double circular boreholes
ZHANG Hang;ZHANG Tianjun;JI Xiang;JI Bing;JI Bingnan;PANG Mingkun;PAN Hongyu
瓦斯预抽钻孔和防冲卸压钻孔协同布置能够一体化防治矿井冲击地压和瓦斯复合灾害,但密集布孔可能会诱发串孔、塌孔等,影响矿井瓦斯抽采效率。为了探究这类双钻孔结构煤岩体受压破坏过程中孔周表面变形及其裂隙演化规律,利用煤岩变形破坏数字图像观测系统对含双圆孔煤样开展单轴压缩条件下的3D-DIC观测实验,获取了不同应力状态下试样表面变形的时间序列图像,通过三维表面重构技术和VIC3D分析处理软件计算得到了试样表面三维全场变形,根据应变场分析结果结合统计指标分析法对应力应变曲线进行了5个变形阶段划分,精细化表征了孔周表面变形和裂隙演化特征。研究结果表明:单轴压缩下含双圆孔煤样应变场灰度整体向高灰度级方向移动,应变场灰度直方图谱峰占比以应力峰值为界先缓慢变化再快速变化;试样孔周径向位移曲线呈现出“从”字型,环向位移曲线呈现出“人”字型,且左孔H1孔周始终沿逆时针方向加速移动,右孔H2孔周始终沿顺时针方向加速移动;孔周裂隙以逆时针错动为主,并伴随着少数裂隙的顺时针错动;应变局部化带外区在加载峰值前主要体现为能量累积,加载峰值后主要表现为能量释放,同时也伴随着部分能量调整转移造成的能量累积;在试样加载过程中,应力场环境、裂隙端部几何形状以及裂隙长度不断发生变化,造成裂隙尖端的应力强度因子
The coordinated arrangement of gas pre-drainage boreholes and anti-impact and pressure relief boreholes can integrate the prevention and control of mine rock burst and gas compound disasters. However, the dense arrangement of these boreholes may lead to the occurrence of phenomena such as string holes and collapse holes, which could potentially impact the efficiency of mine gas extraction. To investigate the deformation around borehole surface and the evolution of fractures during the compression failure process in the coal and rock masses with dual borehole structure, the 3D-DIC observation experiment was conducted on the coal samples containing double circular holes under uniaxial compression conditions using a digital image observation system for coal rock deformation and failure. This experiment yielded some time-series images of sample surface deformation under various stress states. The three-dimensional full-field deformation of the sample surface was calculated using the three-dimensional surface reconstruction technology and VIC3D analysis processing software. Based on the results of strain field analysis, the stress-strain curve was divided into five deformation stages using statistical index analysis methods, providing a detailed description of the deformation and fracture evolution characteristics around the borehole surface. The results show that under uniaxial compression, the grayscale of strain field in the coal samples with double circular holes shifts toward higher gray levels. The proportion of peaks in the strain field gray histogram changes slowly at first and then rapidly, with the peak stress serving as the boundary. The radial displacement curve around the sample holes presents a “
progressive damage;fracture evolution;pore circumferential displacement;fracture tension misalignment;strain energy evolution
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会