Feasibility, design and stability analysis of the major apexes and haulage roads in the block caving method (Case Study: copper deposit in east of Isfahan)

In this paper, by focusing on the deposit which is located in the in eastern of Isfahan as a case study, in the first step, by using fuzzy Nicolas method the appropriate extraction method is selected. The results showed that according to the characteristics of ore deposit, the block caving method is the most suitable method. Then, based on the effective cross-section analysis, the desired range of block caving mine was selected. In the following, the undercut plan, major apex and the draw-bell were designed. Determination of induced stresses and displacement and stability analysis of a suitable support system design is vital, since in the block caving method the major apexes and haulage roads must be stable for a long time. In this paper, the finite difference method is used to determine the induced stresses on the major apex and haulage road when undercutting and draw-bell extraction. The results of the numerical analysis showed that the combination of IP steel and shotcrete support system should be used for the stability of the apexes and the haulage loads. Finally, the IP 120 steel frame and 20 cm thick shotcrete is selected as the proper support system. 

Block caving is a method that is completely based on the principles of caving. This method is based on the assumption that ore fractures and breaks by itself, due to the presence of internal stresses and forces caused by the weight of the ore body and also the downward movement of the broken rocks. The deposit is divided into large blocks, usually square in shape. Each block is undercut completely by a horizontal slot. Gravity forces due to the presence of millions of tons of ore and waste, being in the block and above and around the block, act on the rock masses, and successive fracturing occurs in this way, affecting the entire block in a gradual manner. In the block caving method, the major apexes and haulage roads remain stable for a long time. Therefore, determination of induced stresses and study of their stability and displacement for suitable support system design is vital. 

In this paper, firstly, the appropriate extraction method is selected by using fuzzy Nicolas method. Then, based on the effective cross section analysis, the desired range of block caving mine is selected. Finally, by using numerical molding method the appropriate support system is selected for major apexes and haulage road. 

The results of numerical analysis showed that the combination of steel IP and shotcrete should be used for the stability of the apexes and the haulage loads. Finally, the IP 120 steel frame and 20 cm thick shotcrete is selected as the proper support system.