Point Level Based On Gray Relational Analysis Column Stability Study

In underground mines exploited by point-pillar mining method, the stability and safety of stopes are increasingly outstanding with the carrying on of mining activities.The ore pillar, especially for the point pillar, which is the important structure element determining the stable state of stope, plays a supportive role in stope.It not only maintains the stability of stope roof and surrounding rock, and stable point also has great potential effect on the improvement of ore recovery rate. So the stability of point pillar is increasingly becoming the important issue of stope safety impact and production limitation.However, as the factors of point pillar stability are complex and numerous, identifying the factors and determining their importance have become one of the research difficulties on point pillar stability. The safety stability of point-pillar structure system is one of the key points for point-pillar mining method, and is also the major technical problem that should be solved by mines using point-pillar mining method.The problem of stope stability of point-pillar filling method is studied based on the case of Sanshandao gold mine.The main research topics and results are as follows:(1)The factors affecting the stability of pillar were analyzed in detail, and the hierarchical model for the importance analysis of the influencing factors for pillar stability was established using the Analytic Hierarchy Process (AHP).The factors affecting the stability of point pillar were discussed from the aspects of geology, design and construction, which mainly included mining methods, section size and form of point pillar, point pillar span, point pillar height, orebody characteristics and occurrence conditions,ore and rock physical and chemical properties,in situ stress and natural earthquakes,mining depth, hydrogeological conditions,blasting conditions,supporting conditions,impact of filling and mining operations and so on.Then the importance of the factors affecting the stope stability in Sanshandao gold mine farther was evaluated using the proposed model.The results show that section size of point pillar, in-situ stress state, multiplicating stope blasting and point pillar span are the controlling factors of point pillar stability. (2) Through the analysis of the importance of the factors affecting the stability of the point-pillar method in Sanshandao gold mine, four representative point pillar samples of different point-pillar stopes in Sanshandao gold mine were selected, which were the DZ201# point pillar in the second subarea the fifth layer 24015# (Sample S1),the DZ303# point pillar in the third layer 32000#(Sample S2),the3#DZ201# point pillar in the second layer 24079#(Sample S3)and the DZ302# point pillar in the second subarea the third layer 24063# (Sample S4).On the basis of the weight(importance) determination of the factors of point pillar stability by the Analytic Hierarchy Process(AHP), the risk of point pillar instability associated with the four different conditions were analyzed using the grey correlation grade method, which were also verified in contrast to the pillar stability during practical production process.The results show that the evaluation results of the method accords with the actual situation of point pillar.(3)After the analysis of the point pillar samples in different conditions using the Grey correlation Analytic Hierarchy Process(GAHP), the results of the Grey Correlation Analytic Hierarchy Process used in the stability analysis of point pillar accorded with the practical results associated with the measurement results of field multipoint extensometer and borehole stress-meter, which were proved to be reasonable, safe and reliable.Meanwhile, according to the analysis results of the stability of point pillar associated with different conditions,improvement and its approach were proposed for relatively instable point pillars.As the key issues in stopes mined by point-pillar method, the stability of point pillar is studied using the theories of the Analytic Hierarchy Process and grey correlation degree theory. Aiming at solving the practical problems in mining operations,the research work is of theoretical and engineering application value for the safe, economic and reasonable exploitation of underground resources.