摘要:
钙结岩型铀矿是纳米比亚第二大类型铀矿床,钙结砾岩因其特殊构造而极难破碎,炸药单耗即使达到1.0kg/m3,也会产生大量的大块和超大块,不仅制约铲装作业,严重影响矿山生产,而且极大增加了二次破碎的成本和危险性,是开采过程中遇到的最大难题。为研究爆破作用下钙结砾岩破坏规律,基于损伤断裂力学和波动力学理论揭示了钙结砾岩爆破损伤断裂过程与机理,结合LS-DYNA和Fortran编程建立了包括填隙物、砾岩和界面过渡区的细观数值模型,分析了钙结砾岩爆破应力波传播规律及损伤特征。钙结砾岩爆破损伤断裂过程可分为四个阶段,即:砾石和填隙物均发生压缩破坏;砾石发生拉伸破坏,填隙物发生压缩破坏;砾石和填隙物均发生拉伸破坏;砾石和填隙物交接面发生拉伸破坏。数值结果表明:砾石在爆破荷载作用下表征出更高的等效应力,填隙物等效应力最小,界面过渡区处出现明显的应力集中现象,随着距离的增大砾石和填隙物承受的应力差距减小。砾石的损伤较小,存在损伤“绕石”现象,填隙物的损伤较大。钙结砾岩爆破裂纹的扩展形式主要以沿着应力波的传播方向优先选择物理力学性能较低的填隙物以及交接面进行发育,对于砾石的破坏较弱。爆破块度主要表现为填隙物包裹砾石,爆破块度分布受交接面的粘结力、砾石分布情况的影响。
Abstract:
Calcium conglomerate is the second largest type of uranium deposits in Namibia. Calcium conglomerate is extremely difficult to be broken due to its special structure, and even if the unit consumption of explosives reaches 1.0kg/m3, a large number of large and super-large blocks will be produced, which not only restricts the shoveling operation and seriously affects the production of the mines, but also greatly increases the costs and dangers of the secondary crushing, and it is the biggest problem encountered in the process of mining. In order to study the damage law of calcium conglomerate under the action of blasting, based on the theory of damage fracture mechanics and wave dynamics, the blasting damage fracture process and mechanism of calcium conglomerate were revealed, and the fine numerical model including filler, conglomerate and interface transition zone was established by combining LS-DYNA and Fortran programming, and the blasting stress wave propagation law and damage characteristics of calcium conglomerate were analyzed. The fracture process of the blasting damage of calcium-caking conglomerate can be divided into four stages, namely: compression damage occurs in both conglomerate and filler; tensile damage occurs in conglomerate and compression damage occurs in filler; tensile damage occurs in both conglomerate and filler; and tensile damage occurs in the interfacial interface of conglomerate and filler. Numerical results show that: gravel in the blasting load characterizes a higher equivalent force, the filler equivalent force is the smallest, the interface transition zone at the obvious stress concentration phenomenon, with the increase of the distance between the gravel and the filler to withstand the stress gap decreases. Conglomerate damage is small, there is damage “around the stone” phenomenon, filler damage is larger. Calcium-caking conglomerate blasting crack expansion form is mainly along the direction of propagation of the stress wave to preferentially select the lower mechanical properties of the filler and the development of the intersection surface, the damage to the gravel is weaker. Blasting blockiness is mainly manifested as the gravel wrapped by the filler, and the distribution of blasting blockiness is affected by the bonding force of the intersection surface and the distribution of the gravel.