Study On Underground Pressure Distribution Law And Control Of Safety Pillars Mining Under Buildings

With the continuous decrease of total resources and the rising of mineral resources prices, protective mining of difficult-to-produce reserves under buildings is caused attention by mining experts. In order to get the max recovery ratio, the key point is to ensure the safety of earth’s surface. The project is based on the safety pillars mining under concentrator of western Chengchao Iron Mine. The comprehensive method of theoretical calculation, similar model experiment and numerical simulation is used. The distributed and transferred law of stress are studied in single point pillar and point pillars group. The lateral pressure of backfill is quantitative studied. And this law is used in the safety pillars mining in-375m level of western Chengchao Iron Mine. The original designed parameters are optimized. The major research contents and results are as follow.(1) Similar model experiment and numerical simulation is used in single point pillar experiment. Compared with the results of point pillar before and after filling, a few stress distributed law could be received. The stress is concentrated at the top and bottom of point pillar, and is equally distributed in other parts. And the backfill’s acceleration to point pillar stability is quantitative studied.(2) The comprehensive method of similar model experiment and numerical simulation is used in point pillars group study. The stress distributed law under the pressure stress of overlying rock is found. In point pillars group, the stress of round point pillars transfers to the center, and the stress of round point pillars’top is centrality. The study results show that the center point pillars are easy to damage. The backfill could enhance its lateral pressure to the point pillars with low bearing capacity.(3) According to open stoping and succedent filling method in Chengchao Iron Mine, theoretical calculation and numerical simulation are used in the safety pillars mining in-375m level. The stability of the stope is high, but the recovery ratio is quite low. So point pillar upward cut-and-fill mining method is attempted by numerical simulation study. The stability of point pillars and roof at the stope center is low, instability failure could be appeared. Based on the law of point pillar stability mechanism study, two optimization plans are put forward. They are enhancing the radius of11point pillars and enhancing backfill strength of8drifts in the center of the stope. Through numerical simulation study, the results show that the integrity of point pillars and roof are improved, and the stability of stope is significantly improved. This mining method could enhance the recovery ratio, and it also could ensure the safety of stope and concentrator on the earth’s surface. Therefore, the project could provide guidance to the mining safety progress.