露天转地下开采覆盖层合理厚度优化研究

眼前山铁矿已经进入到露天开采转向地下开采的过渡阶段，地下开采采用无底柱分段 崩落法，该工艺要求露天坑底部应具有一定厚度的覆盖层，以起到挤压爆破和端部放矿的作用。 为了既能满足开采要求，同时又能节省工程成本，矿山需要对覆盖层厚度进行优化设计。根据工 程地质条件与开采工艺，分别利用室内相似材料试验和PFC2D数值分析方法对不同厚度条件下的覆 盖层运动变化规律进行研究。根据实验规律，提出了覆盖层起伏角概念，利用该角度对眼前山铁 矿覆盖层的合理厚度进行优化设计。研究表明：随着覆盖层厚度增加，覆盖层起伏角逐渐减小， 当覆盖层厚度达到35 m后，覆盖层起伏角逐渐趋于稳定的10°左右，因此在考虑滞水与汇水等因 素条件下，确定了覆盖层厚度35 m作为最优方案。根据目前矿山开采运营情况，该厚度覆盖层完 全满足矿山安全生产需要。

Study on the Reasonable Thickness of Overburden in Open-pit to Underground

Yanqianshan Iron Mine has entered into the transition stage from open-pit to underground mining,and the pillarless sublevel caving is adopted in underground mining.In this process,it is required that there should be a certain thickness of overburden at the bottom of the open-pit,so as to play the role in extrusion blasting and end-ore drawing.In order to meet mining requirements and save engineering costs,the thickness of overburden layers should be optimized.Based on the engineering geological conditions and mining technology,the movement and variation rules of overburden layers under different thickness conditions were studied by using similar material test and PFC2D numerical analysis method.According to the experimental rule,the concept of overburden undulation angle is proposed in this paper,which is used to optimize the thickness of the overburden in Yanqianshan Iron Mine.The research shows that as the thickness of the cover layer increases,the undulation angle of the cover layer gradually decreases,when the thickness of the overburden reaches 35 m,the fluctuation angle of the overburden layer gradually tends to be stable at about 10°.Therefore,the overburden thickness of 35 m is determined as the optimal scheme under the consideration of factors such as stagnant water and water catchment.According to the current mining operation,the thickness of the overburden completely meets the needs of mine safety production.