长安金矿无底柱分段崩落法首采中段损失贫化控制方法

长安金矿露天转入地下开采，采用无底柱分段崩落法，出现覆盖层形成困难的问题，且现场矿岩物理力学性质相似，较难区分，使得矿石损失贫化不易控制。为此，设计3种试验方案对3个分段在不同出矿量、不同贫化率条件下展开室内放矿试验研究，优选放矿方案并提出了量化控制方法。试验结果表明：方案1视在回收率和回贫差均高于方案2;其留下的矿石垫层厚度最大，且废石混入率、矿石贫化率均比方案2和方案3低，综合分析方案1为最优方案。首采分段出矿控制有利于保持矿岩界面均匀下降，能够有效缓解覆盖层厚度不足的问题。分析方案1第2分段可知，放出矿量控制在65%～70%时，可以有效地降低矿石贫化率；结合矿石当次品位和当次贫化率随放出矿量的变化关系式，提出了对放出矿量进行相应的量化控制从而有效地降低矿石损失贫化的方法。试验结果在长安金矿1 518、1 509、1 500 m等分段得到实践应用，效果良好，对类似矿山有一定的参考意义。

Depletion control method for loss in the middle section of first mining by bottomless column segmental crumbling method at Chang'an gold mine

During the process of open-pit to underground mining in Chang''an gold mine, the bottomless column segmental crumbling method is used, the problem of difficult formation of overburden layer, and the physical and mechanical properties of the site ore rocks are similar, more difficult to distinguish, and making ore loss depletion is not easy to control. To the end, three experimental schemes were designed to carry out indoor release experiments for three segments with different ore output and depletion rates, to optimize the release scheme, and to propose a quantitative control method. The experimental results show that the apparent recovery rate and poor recovery difference of Scheme 1 are higher than those of Scheme 2; the thickness of the ore bedding left by it is the largest, and the waste rock mixing rate and ore depletion rate are lower than those of Scheme 2 and Scheme 3, and Scheme 1 is the optimal scheme in a comprehensive analysis. The first mining section out of control is conducive to maintaining a uniform descent of the ore rock interface, which can effectively alleviate the problem of insufficient overburden thickness. The analysis of the second section of Option 1 shows that the ore release controlled at 65%-70% can effectively reduce the ore depletion rate; combined with the variation equation of current grade and current depletion rate of ore with the ore release, the method of quantifying the ore release control accordingly to effectively reduce the ore loss depletion is proposed. The experimental results were practically applied in each mining site of 1 518 m, 1 509 m, and 1 500 m sections of Chang''an gold mine, with good results, which have reference significance for similar mines.