further excavation of the cross-section proceeding underneath an already installed part of the structure, e.g. the roof of a tunnel

Full Title

Underground or underwater structures; Retaining walls > Underground structures, e.g. tunnels or galleries, built in the open air or by methods involving disturbance of the ground surface all along the location line; Methods of making them > at least part of the cross-section being constructed in an open excavation or from the ground surface, e.g. assembled in a trench > further excavation of the cross-section proceeding underneath an already installed part of the structure, e.g. the roof of a tunnel

Classification Context

Section:

FIXED CONSTRUCTIONS

Class:

HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL-SHIFTING

Subclass:

FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES