Achieving effective confinement through utilization of non-Newtonian fluid mixture as stemming structure

Abstract The economics of a mining operation is directly influenced by blasting outcomes, where blasting aims to comminute the rock mass in order to attain smaller grain sizes to be loaded and hauled at a minimum cost for its first processing stage. In order to promote adequate rock breakage, the stemming structure needs to provide proper confinement for the borehole charged with explosives, reflecting the energy released during the detonation in form of shock waves and gases to act throughout the in situ rock mass, enlarging its failures and fractures, and also creating new ones. To build up a stemming column, literature recommends the usage of dry granular materials instead of elements with plastic behavior. However, a study was performed using Gypsum plaster as stemming; a kind of material that exhibits solid-like behavior when it is dry. Following this theory, this test verified improvements regarding confinement effectiveness and energy propagation throughout the rock mass when a non-Newtonian mixture (NNM) was applied as stemming; a material that shows a solid-like behavior when is under shear stress. When the stemming arrangement was composed of NNM, it was able to reduce energy and gas losses to the atmosphere, because of the liquid's property of filling voids into the borehole. The NNM yielded high results due to its better confinement effectiveness, a reduction of air overpressure, and an increase of the strain propagation and ground vibration throughout the rock.

摘要 采矿作业的经济效益直接受爆破效果影响，爆破的核心目标为破碎岩体，以获得更小的颗粒粒度，从而在首个加工阶段以最低成本完成装载与转运作业。为实现良好的岩石破碎效果，炮泥（stemming）封堵结构需为装填炸药的炮孔提供有效的围压约束，将爆轰过程中以冲击波和爆生气体形式释放的能量传递至原位岩体，扩大岩体已有裂隙并催生新的断裂面。现有研究文献建议，构筑炮泥柱时应采用干燥颗粒状材料，而非具备塑性变形特性的封堵介质。不过，已有研究采用石膏灰泥作为炮泥开展试验——该材料在干燥状态下呈现类固体力学特性。基于该理论，本次试验验证了采用非牛顿混合物（non-Newtonian mixture, NNM）作为炮泥时的效果提升：该材料在受剪切应力作用时呈现类固体特性。当采用非牛顿混合物构筑封堵结构时，其可借助自身流体特性填充炮孔内的空隙，从而减少能量与爆生气体向大气的逸散损失。非牛顿混合物凭借更优异的围压约束效果、更低的空气超压，以及提升的岩体应变传播与地面振动表现，取得了优异的试验结果。