Rock mass transportation systems in underground mines: consequences and solutions when mining at greater depths

The research presented in this thesis addresses a number of challenges related to rock mass transportation in deep underground mines. In particular, high energy consumption and high exhaust gas emissions from diesel and electric LHDs, the effects of ore pass loss on the loading, hauling and dumping operations due to increasing stresses and increasing costs due to the longer vertical transportation of the rock masses. These critical challenges have been identified by a literature review and analysis of data collected from 15 international deep mines. In order to answer the formulated research questions, three studies on various issues related to rock mass transportation in deep underground mines were made, and the analysis was performed mainly using discrete event simulation. The thesis presents a study of energy consumption and exhaust gas emissions from diesel and electric LHDs with similar bucket sizes. The results show the possible energy savings and a decrease in CO2 emissions when using electric LHDs instead of diesel ones. The thesis also presents a study of the effects of ore pass loss on LHD operations and on the mine production. Maintaining the production with a lower number of operational ore pass structures by increasing the number of LHDs can have a negative effect on the production. This is because an increased number of LHDs in operation will results in increased waiting times for the LHDs and cause variations in the production rate. These variations can be large, causing severe consequences if not managed correctly. The results also show the importance of developing alternative plans for underground loading and hauling operations in case of an ore pass loss. Transportation of rock, especially when mining depth increases, is often associated with high costs and long transportation times. To decrease the amount of unnecessary rock transportation, near-to-face sorting plants may be one alternative. In the thesis, a study was performed on a possible reduction in rock mass transportation to the surface when using this technique. The results conclude that near-to-face sorting plants could lower the environmental effects generated by unnecessary rock transportation to the surface