裂隙砂岩变形破裂过程中应变场及红外辐射温度场演化特征研究

Evolution characteristics of strain field and infrared radiation temperature fieldduring deformation and rupture process of fractured sandstone

采用数字图像相关方法和红外热成像技术非接触式全场观测手段,对不同裂隙倾角的砂岩试件进行单轴压缩试验,引入标准差和近似导数定量地描述应变场和红外辐射温度场的分异程度和分异速率,分析其变形破裂过程中两个领域全场信息的演化规律、变化机制以及前兆异常特征,并探索全场信息之间的相关关系。研究结果表明,裂隙砂岩应变场标准差演化过程可划分为初始分异、初加速分异、中加速分异和快加速分异4个阶段。红外辐射温度场标准差演化过程可划分为初始分异、稳定分异和加速分异3个阶段;应变场和红外辐射温度场标准差在裂隙砂岩变形破裂过程中变化趋势大致类似,两者的皮尔逊相关系数在0.50~0.91之间,呈显著或高度正相关关系;裂隙岩体破裂失稳前应变场分异速率出现2个尖峰,分别对应于张拉裂纹和剪切裂纹起裂点,可视为2个前兆点;红外辐射温度场分异速率在剪切裂纹萌生前呈持续增长,也可视为前兆点。研究成果可为裂隙岩体稳定性监测与预报提供新的手段和理论依据。

Uniaxial compression tests were carried out on sandstone specimens with different fracture angles by means of digital image correlation method and infrared thermal imaging technology,the differentiation degree and rate of strain field and infrared radiation temperature field were quantitatively described by using the standard deviation and approximate derivative.The evolution law,variation mechanism and precursory anomaly characteristics of these two fields during the deformation and rupture processes of the fractured sandstones were analyzed,and their correlations were also discussed.The results show that the evolution process of standard deviation for strain fields can be divided into four stages:initial differentiation,initial acceleration differentiation,intermediate acceleration differentiation and accelerated acceleration differentiation.The evolution process of standard deviation for infrared radiation temperature field can be divided into three stages:initial differentiation,stable differentiation and accelerated differentiation.The standard deviations of strain fields and infrared radiation temperature fields have similar variation trend during the deformation and fracturing process of flawed sandstone specimens.The Pearson correlation coefficients between these two fields are in the range of 0.50 to 0.91,presenting a significant or high positive correlation.There are two peaks in the variation curve of differentiation rate for strain field before failure,corresponding to the initiation points of tensile crack and shear crack,respectively,which could be regarded as two precursor points.The differentiation rate of infrared radiation temperature field increases continuously before the initiation of shear cracks,which could also be regarded as a precursor point.Research results can provide a new method and theoretical basis for monitoring and forecasting the stability of fractured rock masses.