Fragmentation controlled blasting

(1)采用提出的有限元方法对Hopkinson试验中的动态断裂过程进行分析，验证动态拉伸强度与应变率的相关性。明确了应变速率依赖关系是由岩石中的应力集中和重分布机制引起的。岩石的不均匀性也导致了应变速率的依赖性。(2)对某无工作面岩体的断裂过程进行了分析，探讨了断裂模式及其机理。结果表明，施加的压力速率对断裂过程和断裂模式都有影响。准静态断裂过程向动态断裂过程的过渡可以通过由施加压力的传播速度、负荷和上升时间定义的无因次时间来估计。(3)提出了一种结合有限元和有限差分计算的数值模拟方法，分析了应力波和爆轰气体作用下的多重断裂扩展。进一步证实了爆轰气体对裂缝的产生和扩展有较大的影响，气体沿裂缝的数值传播速度与室内实验结果基本一致。结果表明：台阶爆破中沿断口的气速除爆破孔附近外均低于空气声速。(4)提出了一种采用数值分析和图像分析相结合的方法来预测台阶爆破破片粒径分布。该方法采用所提出的有限元方法对台阶爆破的断裂过程进行分析，并通过有限元结果的图像分析对破片大小分布进行评价。(5)采用该方法对台阶爆破中的岩石破碎度进行了研究，明确了爆破条件对岩石破碎度的影响。研究表明，大间距爆破模式能有效地降低破片中的夹持物。此外，还指出，相对于延迟时间而言，现场的最佳破碎程度在很大程度上取决于应力波引起的裂缝中的气体流量。少

(1) The dynamic fracture process in Hopkinson's test was analyzed using proposed finite element method to verify the strain-rate dependency of dynamic tensile strength. It is clarified that the strain-rate dependency is due to the stress concentration and redistribution mechanism in the rock. The rock inhomogenety also contributed to the strain-rate dependency.(2)The fracture process in one free-face rock was analyzed to investigate the fracture pattern and its mechanism. It was cleared that the fracture process as well as the fracture pattern were affected by the applied pressure-rate. The transition between quasi-static and dynamic fracture process can be estimated by the non-dimensional time defined by the propagation velocity, the burden and rise time of the applied pressure.(3)A numerical simulation method, coupled the finite element arid the finite difference calculation, to analyze the multiple fracture propagation due to stress waves and the detonation gas is developed. It is c … More onfirmed that the detonation gas considerably affects the generation and propagation of the fractures and that he numerical gas-propagation velocity along the fractures approximately agrees with that obtained by the laboratory experiments. It is concluded that the gas velocity along the fracture in bench blasting is lower than the air sound velocity except for the vicinity of the blast hole.(4)A method to predict the fragment size distribution in bench blasting using numerical and image analyses was proposed. In this method, the fracture process in bench blasting was analyzed using proposed FEM and fragment size distribution was evaluated by the image analysis of FEM result.(5)Rock fragmentation in bench blasting was examined using proposed method and the influence of blast condition on fragmentation was clarified. It is recognized that the widely spaced blast pattern is effective to reduce the bolder in fragments. Furthermore, it is pointed out that the optimal fragmentation in the field with respect to delay time depends strongly on the gas flow through the fractures caused by the stress wave. Less