Process and mechanism of blasting damage and fracture of calcium conglomerate in Hushan ranium mine
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摘要: 为研究爆破作用下钙结砾岩破坏规律,基于损伤断裂力学理论揭示了钙结砾岩爆破损伤断裂过程与机理,采用LS-DYNA和Fortran编程建立了包括填隙物、砾石和界面过渡区(interfacial transition zone,ITZ)的细观数值模型,分析了钙结砾岩爆炸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4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,ITZ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、砾石分布的影响。Abstract: To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, and the filler experiences significant damage. The expansion of blasting crack in Calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.
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表 1 砾石的基本物理力学参数
Table 1. Basic physical and mechanical parameters of gravel
材料种类 密度/(g·mm−3) 抗压强度/MPa 弹性模量/GPa 泊松比 砾石 2.66 167.8 41.2 0.23 填隙物 2.14 35.0 13.4 0.2 表 2 界面过渡区的K&C本构模型参数
Table 2. K&C constitutive model parameters for interface transition zone
密度/(g·mm−3) 抗压强度/MPa 弹性模量/GPa 泊松比 1.5 25.0 9.3 0.25 表 3 炸药材料参数及状态方程参数
Table 3. Material parameters and state equation parameters of explosive
ρ0/(kg·m−3) D/(m·s−1) $ {p_{\mathrm{CJ}}} $/GPa A/GPa B/GPa R1 R2 1150 4300 3.43 214.4 0.182 4.5 0.9 -
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