Elevator frame for excavation under service duct - traverses offset trench using ram actuated, sidewall which supports pillar under duct until its demolition

摘要

The frame (7) is used to control an excavation beneath an existing service duct. Parallel trenches are cut either side of the duct and eventually the pillar is removed, stability being maintained by filling the trenches with e.g a thixotropic slurry. The cage is lowered in the first trench while the secondary trench is cut, having a ram (10) actuated side wall (8) for the stabilisation and eventual demolition of the pillar. The opposite side wall (13) may be designed to accept lateral pressure, and additional excavating tools (12) may be mounted on the base. The tools may comprise semi-cylindrical excavator buckets, which are used to remove any residual pillar ridge.