Removal of sections of brick or concrete structures.
As part of the refurbishment of a railway station, a new stairwell was to be cut through the top of a brick arched tunnel. Directly above the tunnel there was a solid floor, which was 1 m thick in the middle of the tunnel and 4 m thick at the sides. The aperture was to be cut through all of this material across the full 7 m width of the tunnel for a length of approximately 3 m. This job could have been done with hand-held pneumatic breakers. However, to avoid damage to the base structure, only low-powered units could have been used and the job would involve from 40 to 60 worker days of work. As tools of this type produce typical vibration magnitudes in the range 5 to 20 m/s2 and may be used for long periods, vibration exposures of 7 m/s2 A(8) or greater are possible.
The aperture was made with a large percussive breaker mounted on an excavator. Normally this would have led to severe damage to the remaining arch structure, but this was prevented by cutting right through the brickwork along the edges of the area to be removed. This isolated the delicate parts of the structure and allowed the material to be broken up in approximately 2 hours. The cuts were made in four sections with a diamond wire saw. This consisted of a diamond-toothed saw wire which was wrapped around the structure to be cut and driven by a track-mounted mechanism. As the wire cuts, it is pulled through the structure like a cheese cutter. For this job the wire was threaded through pilot holes drilled through to the tunnel from the floor above. This was done with a clamp-mounted diamond core drill.
Diamond wire cutter (NB The safety guards have been removed for the photograph)
Mounted breaker knocking a hole through a brick arch showing diamond-drilled pilot holes
Slightly cheaper than the price for the same job using hand breakers.
Case courtesy of Specialist Services (Cutting and Drilling) Ltd