Discrete element simulation for evolution characteristics of multi-funnel mineral-rock force chain under flexible isolation layer
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摘要: 為進一步揭示柔性隔離層下散體介質流動過程的內部作用機理,基于離散元軟件PFC開展了柔性隔離層下散體介質流力鏈演化特征的數值試驗研究。結合接觸力學及統計力學相關知識,對多漏斗放礦過程中散體介質體系內力鏈長度、數量、強度、方向和準直系數等的演化特征進行了量化研究。研究發現:多漏斗放礦過程中,強接觸及力鏈接觸占比均比較穩定,其中強接觸占比穩定在33%左右,力鏈接觸占比穩定在16%左右,上下波動幅度均不超過2%;力鏈總數隨著放礦次數的增加不斷波動減少,并在放礦后期穩定在790條左右;不同放礦次數下力鏈長度的概率分布幾乎一致,均隨著力鏈長度的增加呈指數形式遞減;力鏈強度的概率分布隨著放礦次數的增加先呈指數形式上升再呈指數形式下降,并在0.7
$\bar F$ ($\bar F$ 為平均接觸力)處出現一峰值;放礦初始階段,力鏈主要沿鉛垂方向分布,力鏈方向分布形態近似花生狀;此后隨著礦石顆粒的持續放出,散體介質體系內部局部應力集中現象明顯,力鏈分布主方向由1個演變為4個(鉛垂方向、水平方向及與水平方向呈±60°夾角方向);力鏈準直系數隨著放礦次數的增加呈指數形式增長并逐漸保持穩定。Abstract: To further reveal the internal mechanism of the granular media flow process under the flexible isolation layer, numerical experiments on the evolution characteristics of bulk media flow force chain under the flexible isolation layer were carried out based on the discrete element software PFC. Based on a combination of contact mechanics and statistical mechanics, the evolution characteristics of the force chain length, quantity, strength, direction, and the collimation coefficient of the internal bulk medium system in the multi-funnel ore drawing process were quantitatively studied. It is found that the proportions of the strong contact and the force chain contact is found to be relatively stable in the multi-funnel ore drawing process; the proportion of strong contact is stable at about 33%, that of the force chain contact is stable at about 16%, and the fluctuation amplitude is not more than 2%. The total number of force chains decreases with the increase in ore drawing times, and it is stable at 790 strips in the later stage of ore drawing. The probability distribution of the force chain length is almost the same under different ore drawing times, and it decreases exponentially with the increase in the force chain length. The probability distribution of the force chain strength first increases exponentially with the increase in the ore drawing times and then decreases exponentially; it reaches a peak value at 0.7$\bar F$ ($\bar F$ is the average contact force). In the initial ore drawing stage, the force chain is mainly distributed along the vertical direction, and the force chain direction distribution is similar to a peanut shape. After that, with the continuous release of ore particles, the phenomenon of local stress concentration in the granular media system becomes remarkable, and the main direction of the force chain distribution changes to become four (vertical direction, horizontal direction, and angles of ±60° to the horizontal). The force chain collimation coefficient increases exponentially with the increase in drawing times and gradually becomes stable.-
Key words:
- flexible isolation layer /
- granular media /
- force chain /
- synchronous filling /
- discrete element /
- flow law
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表 1 墻體及初始礦石顆粒力學參數
Table 1. Mechanical parameters of walls and initial ore particles
Walls Initial ore particles Shear stiffness /
(N·m?1)Normal stiffness /
(N·m?1)Friction coefficient Normal stiffness /
(N·m?1)Shear stiffness /
(N·m?1)Friction coefficient Ore particle density /
(kg·m?3)Ore particle radius/m 1×107 1×107 0.5 5×107 5×107 0.3 2800 0.008 表 2 隔離層相關參數
Table 2. Parameters related to the isolation layer
Shear stiffness /
(N·m?1)Normal stiffness /
(N·m?1)Parallel bonding
normal stiffness/
(N·m?1)Parallel bonding
shear stiffness /
(N·m?1)Ore particle density /
(kg·m?3)Friction coefficient Elastic modulus of parallel bond /Pa Ore particle radius /m 1×107 1×107 1×106 1×106 2000 0.4 5×107 0.0015 表 3 礦石顆粒參數
Table 3. Parameters of ore particles
Shear stiffness /
(N·m?1)Normal stiffness /
(N·m?1)Friction coefficient Linear friction coefficient
against rollingOre particle density /
(kg·m?3)Ore particle radius /
m5×107 5×107 0.5 0.5 2800 0.008 表 4 多漏斗放礦過程力鏈方向分布的擬合結果
Table 4. Fitting results of the force chain direction distribution in the multi-funnel ore drawing process
Ore drawing times f0 an θn 1 1.00 0.30 94.58 2 1.00 0.30 91.48 3 1.00 0.36 87.35 4 1.00 0.42 92.90 5 1.00 0.40 88.42 6 1.00 0.42 90.59 7 1.00 0.38 88.20 8 1.00 0.35 82.32 9 1.00 0.36 87.91 10 1.00 0.27 95.02 11 1.00 0.46 79.60 12 1.00 0.49 79.55 259luxu-164 -
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