爆炸荷载作用下岩石的变形与破坏研究(Ⅰ)

Study of Deformation and Failure of Rock under Explosion Load (Part I )

无论是矿山工程、隧道工程中钻孔爆破效率的提高、工程爆破领域爆破振动参数的预测,还是最近一系列高技术常规局部战争中钻地炸弹对地下坚固目标的破坏,在不考虑岩石中强爆炸引起的光子和电磁辐射等极端效应情况下,都亟待要求对岩石中爆炸引起的应力、变形及其它运动参数和破坏效应作出比较准确的评估。目前对此问题的研究尚只能达到大致的机理及景象的定性认识和描述,定量上的确定存在数量级的误差,尤其是爆炸和冲击的近区,误差更大。其原因在于岩石中爆炸产生的变形和破坏特征,不仅与作用时发生相应的物理及力学运动密切相关,而且强烈地受岩石自身构造缺陷水平及其变化的制约。本文概述了爆炸作用下岩石的动力变形与破坏研究之现状。研究中考虑了岩石的构造特点及其对基本力学性状的影响,并简述了其研究的新趋向。

This paper reviews the progress of dynamic deformation and failure effects of rock under explosion. The behavior of rock materials under intensive dynamic loading is a complex problem, but has impor- tant practical meaning. Not only physical mechanical properties of rocks, but the loading pattern determine the behavior of rocks. Besides the study of macroscopic behavior of rocks with the help of continuum mechanics, as a current trend, the study of microscopic behavior of rocks is carried out intensively. The goal of the given study lies in study of the impact of physical mechanical properties of rocks and the loading speed on the deformation and fracture of rocks in consideration of micro-macroscopic behavior. The microscopic physical kinetic mechanism of deformation and damage of materials is investigated firstly. The study shows that the deformation and damage process is the process for material particles to overcome energy barriers, the kinetic evolution equation of deformation and damage for different stress states are given,and Zhurkov's formula, Alexandrov's strain rate equation, damage evolution equations of Norton and Kachanov are also derived, hence their intrinsic relationship is shown . And at the same time the deformation and damage process is also a structural change process at different structural levels including micro-, meso-, and macroscopic levels. The changes at different levels have their own characteristics. At microscopic level, the deformation and damage process for polycrystalline materials is a kinetic process of generation and growth of dislocations. At mesoscopic level, the basic carriers of plastic flow are 3-di-mensional structural elements, the feature of their deformation is 'shear plus rotation'. At mesoscopic level, plastic deformation is related to the formation of dissipative substructures and the fragmentation of deformation, and fracture is the final stage of fragmentation of deformable bodies. At macroscopic level, the description of deformation and damage is based on continuum mechanics, but the contribution at the micro- and mesoscopic levels must be considered. The contributions at the micro- and mesoscopic levels may be considered in the governing equations by giving the plastic shear strain rate and the contribution to shear strength. At microscopic level, the shear strength of materials is determined by the evolution of dislocation continuum, but at mesoscopic level it is determined by the mesostructures and the formation of new mesoscopic substructures. Therefore in the modeling of large stress-strain curves, not only the evolution of internal microstructures, but also the formation of different substructures and their contributions to flow stress are considered. It is shown in the analysis that strength-strain speed dependency is dominated by the thermally activated mechanism in lowest strain rate region. With the increasing of strain rate, viscous mechanism will dominate gradually. In the utmost strain rate region, the thermally activated mechanism dominates again. One model of strength-strain speed dependence is suggested. One elastic-plastic model and one Mohr-Coulomb model in consideration of strength-strain speed dependence are given. In the last part of chapter constitutive relationship of porous elastic-plastic materials is investigated. Based on the thermodynamic law, Derived form free energy function by effective strain method, the brief and relatively simple equations of state of porous elastic-plastic materials under intensive dynamic loading are given, and also the equations of deviatoric deformation are given.