Numerical Investigation on Safe Mining of Residual Pillar in Goaf: A Case Study of Panlong Lead-Zinc Mine

In order to verify the residual pillars in underground goaf can be mined after filling the underground goaf with filling materials, the three-dimensional refined model is established to simulate the process of mining residual pillars. The residual pillars include interstall pillars (IP) and top pillars (TP). The rock mechanics test and different proportioning tests of filling materials have been carried out. Three schemes for mining residual pillars have been proposed. According to the engineering situation of the mine, the numerical models corresponding to the three schemes are established, such as model1 (M1), model2 (M2), model3 (M3). The MIDAS-GTS/NX software is used to build three-dimensional mine model of different mining scheme. Two criteria were used to determine whether the pillar can be mined, which are the deformation of the strata and the distribution of the plastic zone. Finally, the residual pillars that can be mined are discussed. The results show that some of residual pillar can be mined after filling the goaf with filling body material. The mining of the residual pillar causes the strata deformation and the plastic zone in the rock mass. According to the numerical simulation results, different ore quantity can be mined with different mining schemes. Compared with the other two mining schemes, the scheme 3 (M3) has little effect on the strata deformation and the formation of plastic zone. Moreover, the 8.61 x 10(8) kg (63% of the total) ore body can be mined with the scheme 3 (M3). The conclusion can be used for reference in similar mine.