Justification of applicability of the mosaic pillar system in the ore-free blocks in mining of lode gold deposits

Abstract

The paper discusses the formation of self-similar, hierarchically scaled, fractal properties of ore and ore-free subsystems of blocks within the mineralized zone. It is planned to identify the ore-free invariant blocks to create pillars within the extended producing block boundaries with the size of up to 160 m along the strike and up to 120 m down the dip of the thin veins, for mechanized layer-wise mining from sublevel strikes. Subsystems of the ore and ore-free blocks have similar fractal dimensions and degree of hierarchy, which is close to the coefficient of 2. Application of the method to leave the ore-free intervals as pillars considerably reduces the specific operational costs from 28-34 USD/ton of ore to 16,64 USD/ton due to cutting costs of drilling and blasting operations of the pillar volume (up to 14%) as well as for the mine preparation and stoping operations. The method of leaving pillars in the ore-free intervals makes it possible (1) to abandon the practice of rock and consolidating stowing while cutting the specific costs down to 5.18 USD/ton of ore; (2) to control the rock pressure while mining lode bodies in the vertical extent with cascades up to 120 m and the expected mineralization mining depth of up to 1000 m; (3) to enhance the produced ore grades from 14% to 25% by minimizing the primary dilution from the ore-free intervals.