What are the advantages and disadvantages of using raise boring vs. conventional methods for creating ventilation shafts?

Raise boring and conventional methods are two distinct approaches to creating ventilation shafts in underground mines, each with its own advantages and disadvantages. Raise boring is a mechanical excavation method that involves drilling a pilot hole from the surface to the underground workings and then using a raise bore machine to enlarge the hole to the desired shaft diameter by pulling a rotating cutter head upwards. Conventional methods, on the other hand, involve drilling and blasting from either the surface downwards or from the underground workings upwards. The advantages of raise boring include safety. Raise boring is generally safer than conventional methods because it eliminates the need for miners to work in an unsupported excavation. There is no exposure to falling rock or other hazards associated with drilling and blasting. It also offers faster excavation speed. Raise boring can excavate shafts much faster than conventional methods, especially for large-diameter shafts. The process is continuous and automated, reducing the need for manual labor. The method creates smoother shaft walls. Raise boring produces smoother shaft walls than conventional methods, reducing the need for additional support or lining. The smooth walls also reduce air resistance, improv....