Frontier-Kemper has constructed more than 100 miles of tunnels using tunnel boring machines (TBMs). TBMs excavate underground tunnels using a circular cross section cutter head at the front of the machine to cut through and grind rock (hard rock TBM tunneling) and to cut and mix soft ground deposits (Earth Pressure Balance and Slurry TBM Tunneling). This material is then conveyed to the construction site from the rear of the machine with a host of different methods—conventional rolling stock (muck car) transport, continuous horizontal conveyor belt, or pumping and transport of slurry lines. Advancements in TBM excavation methods limit disturbances to surrounding areas and limit settlement in soft ground deposits to acceptable limits with no detrimental effect to structures above.
