无底柱分段崩落法不同回采顺序的损失贫化研究

Research on Loss and Dilution by Different Mining Sequence in Pillarless Sublevel Caving

无底柱分段崩落法的回采顺序对矿石的损失贫化有很大影响。大红山铁矿井下受到露天压矿的影响,以70°为压矿界限,必须先回收可采矿体,待解除露天压矿之后再回收被压矿体。目前所研究的损失贫化大多是基于上分段采完再采下分段的情况,对这种先采矿体一侧再采另一侧形成的高落差引起矿石的损失贫化研究甚少。使用实验室物理放矿模拟对上述分期出矿和正常回采顺序出矿的损失贫化进行了对比研究,结果发现分期出矿回贫差指标低于正常出矿7.1个百分点。分析发现正常出矿的矿岩接触面是连续的,而分期出矿被截断成2个不同标高的"V"形接触带,使废石混入面增多,导致贫化率比正常出矿高。研究还发现随着放矿落差的增大,回贫差在缓慢减小。最后建议矿山尽可能地降低放矿之间的落差,或者采用低贫化放矿的方式进行出矿,以保留70°矿岩接触带来控制损失贫化。

Mining sequence in pillarless sublevel caving has a great influence on ore loss and dilution. Underground mining in Dahongshan iron ore is affected by open pit mining. With 70° as the ore boundaries, recoverable ore must be recovered first,then the left ore is recovered until the pressure over the left ore is moved. Current researches on loss and dilution are mostly based on the case of mining upper sublevel first and then the lower sublevel. But research on loss and dilution resulting from high fall formed by first mining one side then mining the other side is less. The loss and dilution rate by above stages of ore removal and normal mining sequence was compared using laboratory physical simulation. The results showed that the loss and dilution by stages of ore removal was lower by 7.1 percent point than that of the normal mining. Analysis found that the rock contact zone by normal mining was continuous, while the contact zone by staging was cut off into two different elevations of ＂V＂ shaped,which lead to the waste rock surface increased, resulting in high dilution rate than the normal. The study also found that as the ore drawing gap increased, the recovery-dilution index decreased slowly. It is finally recommended that the mine should reduce the fall as much as possible or use the low dilution ore drawing to retain the 70°ore-rock contact zone in or- der to control the loss and dilution.