炸药单耗对赤铁矿爆破块度的影响规律数值模拟研究

Numerical Study on Relationship between Specific Charge and Fragmentation Distribution of Hematite

通过在连续-非连续单元方法(CDEM)中引入朗道点火爆炸模型及岩体塑性-损伤-断裂模型,实现了赤铁矿爆破破碎过程的模拟。提出了5个评价爆破后块度分布特征的指标,分别为平均破碎尺寸(d50)、极限破碎尺寸(d90)、块体不均匀系数(d90/d50)、系统破裂度(Fr)及大块率(Br)。基于CDEM方法及上述5个评价指标,分析了改变炮孔直径、改变间排距等两种改变炸药单耗的方式对赤铁矿爆破块度的影响规律。数值计算结果表明:随着炸药单耗的增大,赤铁矿的破碎尺寸逐渐减小;相同炸药单耗情况下,改变炮孔直径的破碎效果略优于改变间排距的破碎效果。在双对数坐标下,随着炸药单耗的增大,平均破碎尺寸(d50)及极限破碎尺寸(d90)均线性减小;采用衰减型幂函数进行了拟合,给出了平均破碎尺寸(d50)及极限破碎尺寸(d90)与炸药单耗间的函数关系。随着炸药单耗的增加,块体不均匀系数(d90/d50)及系统破裂度(Fr)均逐渐增大,而大块率(Br)则迅速减小。当炸药单耗大于0.25 kg/t时,大块率(Br)已经小于0.5%;当炸药单耗超过0.6 kg/t时,大块率(Br)为0.0%。

By introducing Landau blasting model and rock plastic-damage-fracture model into Continuum Discontinuum Element Method（ CDEM）,the simulation of hematite fragmentation process under blasting load was realized.Five indicators to evaluate the block distribution feature after blasting were proposed,including the average fragmentation size（ d50）,ultimate fragmentation size（ d90）,block nonuniform coefficient（ d90/ d50）,system fracture degree（ Fr） and large block ratio（ Br）. Based on CDEM and the five evaluation indicators,the relationship between spcific charge and fragmentation distribution characteristic was studied. Two ways to change the spcific charge was discussed on changing bore hole diameter and changing row column distance. Numerical results show that,with the increase of spcific charge,the hematite fragmentation size decreased gradually; with the same spcific charge,the fragmentation quality obtained from changing bore hole diameter was better than which from changing row column distance. In double logarithmic coordinates,with the increase of spcific charge,average fragmentation size（ d50） and ultimate fragmentation size（ d90） all decreased linearly,and decaying power function was used to fit the relationship between d50,d90 and spcific charge. With the increase of spcific charge,the block nonuniform coefficient（ d90/ d50） and system fracture degree（ Fr） all increased gradually,while the large block ratio（ Br） decreased sharply. When the spcificcharge was larger than 0. 25 kg / t,the large block ratio（ Br） was less than 0. 5%; while the spcific charge exceeded0. 6 kg / t,the large block ratio（ Br） turned to be zero.