187
Special Lecture /
Conférences spéciales
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
walls were installed after a complex phase of works (bulk
excavation, soil treatment, micropiles, Berlin wall, and
strutting).
Soletanche Bachy had been aware of the presence of old
king posts which had been used as temporary supports during
the construction of the 1985 station and left in place. The
accurate position of these obstructions were unknown and a
detailed working procedure for the removal of these
obstructions was put in place covering safe access lighting and
air supply. When a King Post was encountered during pipe
ramming, the auger was used to clean the pipe and the steel
profile exposed. Following strict safety procedures, a worker
was sent into the pipe to clean around the profile and it was then
cut into smaller pieces for removal back through the pipe.
Figure 13. Pipe jacking and mining – South Wing.
Under the station, all the pipes were driven to the existing
diaphragm walls and had to be anchored into them. The initial
design indicated the pipes being driven 500mm into the
opposing wall. However, as well as the impracticalities of doing
so, the Authorities had rejected this scheme through concern for
damage to the existing structure.
Soletanche Bachy proposed to tie in the pipes, using drilled
reinforcement bars. An innovative system was developed by
Soletanche Bachy. A guide was fabricated and inserted into the
pipe. This guide was positioned at the end of the pipe up against
the opposing wall and cores were then drilled into the
diaphragm wall using the guide to ensure accurate positioning
of the dowel bars which were sealed using an adhesive capsule.
Figure 14. The “Gun” for the Ø600 pipes.
Figure 15. Drilling in the soil nails using the Springsol.
Figure 16. The Springsol tool, unfolded.
