Study On Optimization Of Stope Structure Parameters In A Tungsten Mine Using Room-pillar Method

For the mine adopting room-pillar method for mining,the stability of stope is strongly related to the production of ore and the safety of operators.The refined design of stope structure is required to ensure the stability of the stope and to obtain the maximum recovery rate.In order to optimize the structural parameters of a tungsten mine,the mechanical parameters of rock mass are determined by field investigations and laboratory tests.The mechanical model of roof-pillar system is further established to obtain the optimal stope structure parameters.At last,the numerical simulation method is used to verify that the stope structure parameters can be used in the field.Based on these researches,the main results are as follows:(1)The laboratory mechanical experiments were carried out on the rock samples from the tungsten mine,and the structural plane of the mine was investigated comprehensively.Then the mechanical parameters of rock mass were determined by Hoek brown rock mass failure criterion,which laid a foundation for the subsequent theoretical analysis and numerical simulation.(2)The top pressure distribution of square stope is estimated by using the natural balance arch theory.The optimal width of the boundary pillars is 7m when the roadway and goaf are stable by using A.H.Wilson elastic core area theory and its related theories.(3)By solving the mechanical model control equation of roof-pillar system based on elastic foundation,the average width of pillars with 9,16 and 25 pillars are obtained when the roof is stable under different boundary conditions.The relationship between the total support area of pillars and the parameters of roof under different boundary conditions is analyzed.By solving the mechanical model of roof-pillar system based on elastic point support,the width of pillars in different positions is obtained,and the reasons for the variation of pillar width influenced by their distribution position are analyzed.The results show that the thickness of roof has the greatest influence on the total support area of pillars;Whether the top pressure is uniform load or not,when the pillars does not excessive support,the width of the pillar is inversely proportional to the distance from the center of the stope to pillars,which is affected by the size of the stope.(4)Combined with the recovery rate,the paper analyzes the stope structure parameters calculated by the above two roof pillar system mechanics models.The best stope structural parameters are obtained when the stope is stable: the width of the boundary pillar is 7m,the number of pillars in the stope is 16.According to the classification of the distance from the center of the stope to pillars,the width of pillars under the fixed support boundary is set to be 9.55 m,8.29 m,7.23 m,and the corresponding recovery rate is 74%;The width of pillars under simply supported boundary is set to be 9.55 m,8.93 m and 8.22 m,and the corresponding recovery rate is71%.The numerical model is established by using the best stope structural parameters above and calculated by FLAC3 D software.The simulation results show that the best stope structure parameters are enough to maintain the stope stability.A new set of stope structure parameters are provided for the mine.