The chief characteristic of the caving mining method is that caved ores, surrounded by overlying rocks, are drawn from the drawpoint. And the ultimate objective of investigating the draw problems is to forecast the ore loss and dilution. In this paper, the rolling resistance model in the Particle Flow Code was used to simulate the effect of actual shape of different materials flowing towards a drawpoint under the near-field condition and improve the computational efficiency at the same time. The reliability of the rolling resistance model was validated against experimental results, and the new empirical equations were deduced for calculation of the ore dilution rates based on the upside-down drop shape theory (UDDS theory). Within the precision and range of values considered in this paper, the results show that when the height of IEZ is in the range of 30–80 m, the particle size, the drawpoint size and the column height have no significant influence on the (isolated extraction zone) IEZ’s shape and maximal width. And regardless of near-field gravity flow with one or two granular materials, the shape of IEZ was coincident with the upside-down drop shape.

中文翻译：

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使用滚动阻力模型和倒滴形理论计算矿石稀释率的数值方法

崩落采矿法的主要特点是从出矿点抽取被覆岩包围的崩落矿石。调查开采问题的最终目标是预测矿石损失和稀释。本文利用粒子流代码中的滚动阻力模型来模拟近场条件下不同材料的实际形状流向拉点的效果，同时提高计算效率。通过实验结果验证了滚动阻力模型的可靠性，并基于倒滴形理论（UDDS理论）推导出了新的经验方程用于计算矿石稀释率。在本文考虑的精度和数值范围内，结果表明，当IEZ高度在30-80 m范围内时，粒度、拉点尺寸和柱高对（隔离提取区）IEZ的形状和最大宽度没有显着影响。并且无论是近场重力流的一种还是两种颗粒材料，IEZ的形状都与倒置的水滴形状重合。