Abstract: A Tunnel Boring Machine (TBM) with a circular cutting profile includes secondary cutterhead components that produce a semicircular-arched tunnel profile for use in underground mining and/or civil construction operations, e.g., for boring in material containing rocks with Unconfined Compressive Strength (UCS) of up to 200 MPA or stronger. The machine is particularly suited to excavate long access tunnels, mine development drifts, road tunnels, and other types of tunnels that require flat bottom, semicircular-arched profiles. The substantially flat tunnel floor allows immediate and effective use of standard vehicles for material and crew transport as well as other construction and mining activities.

Abstract: A belt tension-reducing device is provided, which includes a support member; a pliable central wheel assembly configured to engage a both downwardly and upwardly moving portions of the conveyor belt; first and second outboard roller assemblies positioned to engage the downwardly and upwardly moving portions, respectively. A second effective rolling radius of the pliable central wheel assembly at a contact point with the upwardly moving portion of the conveyor belt can be greater than a first effective rolling radius of the pliable central wheel assembly at a contact point with the downwardly moving portion of the conveyor belt to reduce stresses on the belt in a vertical shaft. The belt tension-reducing devices can be arranged in a stacked configuration within the vertical shaft.