Tunnel boring machines (TBM) are used in subsurface mining operations to excavate tunnels through rock strata and surrounding sedimentary deposits. They consist of a rotating cutting wheel fitted to a series of thrusting mechanisms and conveyors used to advance the machine forward.
TBMs can be classified as hard rock or soft ground machines. Hard rock tunnel boring machines are designed and used for boring through solid rock and solid aggregate. Soft ground machines are used to tunnel through hydrated soil and unconsolidated sediments, and may be further optimized based on the hydration and stability of intended ground conditions.
TBMs for boring through hard rock (left) and soft, unstable ground (right).
Image credit: Herrenknecht | Robbins