Underground gallery arch construction - uses sections forming successive rings arranged in helix, thrust forward by hydraulic rams

摘要

The construction method for an underground gallery uses walls made up from arch sections, assembled in successive rings. These follow the advancement of a shield thrust by hydraulic rams on the last ring formed. For continuous advance, the rings are helical. The helix pitch is the same as the longitudinal length of the ring. The rams press perpendicularly on to the rings using a flat surface on the ram thrust face. The elements form outer (1) and inner (1a) wall faces and also front (3) and rear (3a) faces for the thrust face.