STABILITY OF BOUNDARY PILLARS FOR TRANSITION FROM OPEN PIT TO UNDERGROUND MINING

The stability of boundary pillar,which can be found across in mine shifting from open-pit to underground mining,is very important for safe production of underground mine. Based on the practice of Shirengou ore mine from open-pit to underground mining,the stabilities of boundary pillar at representative sections are calculated and analyzed by using the methods of limit equilibrium and numerical simulation. With the application of the limit equilibrium method and consideration of the thickness,span of boundary pillar,height of deposed rock,and obliquity of ore mine,the safety coefficients of all sections of boundary pillar are calculated, respectively. The safe thickness for boundary pillar has been modeled by the RFPA2D (rock failure process analysis)system,including deformation and failure of boundary pillar during caving. At the same time,the failure process of the different sections is simulated. By calculation,the safety and danger section of the boundary pillar is predicted. It validates the designed boundary pillar thickness and offers references to construction.