为了研究循环加载条件下岩石的变形演化规律,开展了红砂岩试件的等幅循环加载与分级等幅循环加载试验.采用CCD相机对试验过程中试件的变形图像进行采集,基于数字散斑相关方法分析了等幅循环加载过程中试件的非均匀变形演化规律.分析研究发现:循环加载过程中,随着循环次数的增加,试件的非均匀变形场逐步演化,变形局部化现象愈加明显;非均匀变形在循环加载过程中存在时间滞后和变形累积特征,且分级等幅循环加载过程中其峰值应力的增加会使非均匀变形的滞后特性与累积特征更加明显;在试件发生破坏前,加载顶点和卸载底点的非均匀变形指标数值逐渐接近.研究循环加载作用下岩石的非均匀变形演化规律,可为岩石破坏提供新的前兆信息.

In this study, uniaxial cyclic loading tests were carried out on granite specimens to study the relationship between acoustic emission (AE) characteristics and non-uniform deformation of rock materials during the cyclic loading process. The AE signals and the deformation images of the specimen surfaces were collected by using the AE system and CCD camera in the deformation and failure process, respectively. Combined with the digital speckle correlation method, the AE characteristics of specimens were investigated during the evolution process of non-uniform deformation. The research results showed that the minimum point of non-uniform deformation corresponded to the lowest point of unloading stress during each cyclic loading process. However, after the startup of the localisation band, the maximum point of non-uniform deformation lagged behind the vertex of loading stress in each cyclic loading process. There was a good correspondence between the non-uniform deformation evolution and the AE signal. During the cyclic loading process, the first turning and increasing point of non-uniform deformation is the starting point of the increase of AE signal, whereas the maximum point of non-uniform deformation is the starting point of the quiet period of the AE signal. With the increase of cyclic number, the degree of non-uniform deformation is negatively correlated with the Felicity ratio, that is, the greater the non-uniform deformation is, the greater the damage degree is, and the smaller the Felicity ratio is.

The similar simulation experiment platform for the temperature field of surrounding rock in roadway was established based on similarity theory. It was made possible to verify simulation results of the Finite Volume Method. In order to reveal the heat dissipation rules in roadway, the mathematical model of transient temperature field for the surrounding rock in roadway was established, and dimensionless parameters were introduced into the model to make the model non-dimensional. The Finite Volume Method based on triangular mesh was used to discretize the dimensionless equation and the dimensionless temperature distribution for the transient temperature field of surrounding rock in roadway was obtained. At the wall face in roadway, the dimensionless temperature decreases gradually with the increase of Biot coefficient and Fourier coefficient, and finally tends to a certain value. The curves of the unstable heat transfer criterion and the corresponding laws of variation were obtained by further calculation. The numerical results have shown that the unstable heat transfer criterion decreases with the increase of the Fourier number at a constant Biot coefficient, while it increases with the increase of Biot coefficient at a constant Fourier coefficient. The research results in this paper provide a simple and reliable algorithm to determine the unstable heat transfer criterion derived from the corresponding parameter values of an arbitrary transient temperature field of surrounding rock in roadway. For mine cooling technicians, it provides important reference basis to calculate the chilling requirements and study the heat dissipation rules of surrounding rock in roadway.

通过砂岩试样的单轴等幅循环加卸载实验,分析试样变形过程中能量变化特征.分析实验结果,发现卸载过程中,应力-应变曲线表现出明显的应变滞后现象;分析滞后能发现随着循环次数的增加,滞后能逐渐减小;不同的等幅加卸载过程,岩样能量分布略有不同,随着循环次数的增加,耗散能逐渐减小,弹性能基本保持稳定.

Based on the triaxial compression tests of sandstone under constant confining pressures, stress-strain curves under different confining pressures were obtained. Based on the volumetric strain of cracks in the compression process, damage variable was defined and the increment of the volumetric strain of cracks was assumed to follow Weibull distribution. In consideration of the nonlinear elastic properties and the effect of residual stress in the process of rock compression, and based on strain equivalence hypothesis, the statistical damage constitutive model of sandstone under triaxial compression was deduced theoretically. The theoretical model was verified by experiments, and the physical meaning and change laws of each model parameter under different confining pressures were also discussed. The research results show that the model is correct and reasonable.

基于恒定围压下砂岩的三轴压缩试验,得到不同围压下的应力应变曲线.认为压缩过程中的体积应变是由基体材料的弹性体积应变和裂隙体积应变组成,通过计算得到裂隙体积应变在压缩过程中各阶段随各应力、应变的变化关系,从而得到裂隙演化规律.