【作者】 胡柳青；

【导师】 李夕兵；

【作者基本信息】 中南大学 ， 安全技术及工程， 2005， 博士

【摘要】 该文对冲击载荷作用下的岩石断裂机理进行了比较全面和系统的研究,从微观、细观与宏观三个层次对岩石断裂过程特性及其动力响应进行了分析,其主要工作如下: 1、对三种典型应力波分别利用傅立叶变换与小波变换进行了对比分析,得知了它们的频率分布以及能量分布规律;针对冲击载荷的作用特点,提出了由冲击载荷所引起的应力波波长、岩石的缺陷尺寸以及试件尺寸之间的大小关系作为宏观、细观与微观尺度划分标准。 2、针对冲击载荷作用下岩石断裂的微观热力学过程为绝热过程或准绝热过程,利用热力学理论与冲击作用下岩石的物态方程,得出了此状态下的岩石本构关系,并提出了冲击载荷作用下岩石微观热力学破坏条件。 3、通过分析单一有限尺寸裂纹在应力波作用时的近裂纹面应力场,得出了影响其动态应力强度因子的主要因素是应力释放区大小以及应力释放区外的应力分布。在此基础上,构建了用于计算动态应力强度因子的近似表达式。通过对垂直方向、切线方向以及斜向冲击载荷作用下的动态响应进行的数值模拟,得到了各种状况下的动态应力强度因子,同时获悉了最优断裂条件下应力波入射情况。 4、对应力波在软弱结构面以及节理裂隙处传播的特征进行了系统的研究,探讨了岩石动态断裂过程中的应力波波形畸变的问题。针对软弱结构面上的摩擦滑移准则的局限性,引入能量损耗值来表示界面可滑移的程度或趋势大小,把单点上的可滑移条件下的能量动力准则推广到整个结构面上,并从应力准则的角度验证了此方法的可行性。通过对应力波在张开型节理裂隙处传播规律的解析分析,得出了细观缺陷的几何结构、物理特性对应力波传播的影响。通过重点考查SHPB压杆实验中反射波的变化情况,指出其反射波的变化过程能反映岩石的动态累积损伤或动态断裂过程。 5、考虑到岩石动态断裂的相关因素以及应力波作用的特点,以能量更多还原

【Abstract】 The thesis has systematically investigated the mechanism of dynamic fracture processes of rock subjected to impact loads. The dynamic characteristics and responses of the rock fracture processes have been analyzed from micro, meso and macro levels respectively. The thesis includes the following work.1. Three typical stress waves induced by impact loads were analyzed by both Fast Fourier Transform (FFT) and Wavelet, and the distribution rules of frequency and energy of stress waves were obtained. According to the trait of the impact loading, the paper proposed that the size relation between the wavelength of stress waves induced by impact loads, faults in rock and the samples may be used for the classification criterion among the micro, meso and macro dimensions.2. The dynamic fracture processes of rock under impact loading are regarded as adiabatic or quasi-adiabatic processes in micro thermodynamics. Associated with the state equation of rock subjected to impact loading, the constitutive relation of rock suitable for this situation was obtained, and the breakage condition of micro thermodynamics for rock under the impact loading was proposed.3. The stress field near the crack subjected to impact loads was investigated. The main factors, which have effect on dynamic stress intensity factor (DSIF), are the size of the stress releasing zone and the distribution of the stress out of the release zone. The calculation formula of DSIF was proposed. The dynamic responses of crack subjected several typical impact stresses such as shear, normal and oblique incident stress waves were simulated. According to the results of the simulation the DSIFs were calculated. The angle of initiation of the crack was predicted. The method ofoptimizing fracture generating by stress pulses was discussed.4. The propagation characteristics of the stress waves transmitting to the weak interface or opened crack was investigated systematically. For its limitation, the energy criterion under the sliding condition for one point was generalized to the whole interface by inducting the dissipating energy value to indicate the possibility of slide. This method was verified by the stress criterion; The geometry of opened crack and its physical property have effect on the propagation of stress waves according to analytical results; The deformations of reflected stress waves recorded in the SHPB tests were investigated emphatically, and the process of the change of the reflected stress waves refers to the process of dynamic damage cumulation or the dynamic fracture.5. Based upon the study on rock responses to impact load by the principles of energy dissipations and associating with the damage mechanics and the action density of the stress waves as well, the dynamic cumulative damage formula of rock under dynamic cyclic loading at the damage phase was proposed. According to the fractal phenomenon analysis on rock fragments, the iterative relationship expression about the damage fractal value and the number of the fragments of rock subjecting to impact load was obtained. At the same time, the iterative relationship expression about the damage fractal value and the impact energy was proposed basing on the principles of energy dissipations and the criteria of dynamic brittle fracture. The results of tests show that the relation among the impact energy, the damage of rock and the number of fragments lies in a state of mutual coupling.更多还原