The stability theory and monitoring comprehensive evaluation analysis of near-surface mining in Ningdu pyrite mine

Ningdu pyrite is mined by the column-and-pillar method with a ground elevation of +240 m and an elevation of +190 m at the middle of the upper mining section. However, the upper middle section of the mining area is no more than 50 m above the ground surface and no filling and reinforcement measures have been adopted since the mining.The stratum stability analysis of the stratum with the critical layer and the failure limit span of rock strata is carried out. The result shows that the stratum overlying stratum is stable under the condition of 8 m span.The result shows that the overlying strata is stable under the condition of 8 m stope.The gray system prediction model is used for comparative analysis. The results show that the predicted settlement value is basically consistent with the actual monitoring settlement value, indicating that it is credible and can be applied to the settlement prediction.According to the actual situation of the mine, long-term surface subsidence monitoring was carried out and the change curve was compiled. The result shows that the settlement of the mine resulted in settlement within the acceptable range, But it must attract enough attention.