Retaining walls at Bayview Station

The new Bayview Station site is always interesting to watch. Remember what the old western abutment looked like?:

The old abutment was removed, new pillars were constructed, and a new wall is being built to conceal the supporting bridge pillars:

The pattern of the cladding should look somewhat familiar as it is meant to blend with the existing wall of the old Transitway viaduct. (With a little less graffiti; but that will soon change, I’m sure.)

The blocks at the corners are flat-sided, and don’t knit together, but the idea is there. Note that since this bridge will also have the platforms sticking out both sides, the structure needs to be wider than the viaduct. This accounts for those corners, as the wall bumps out around the piers.

Notice also in the above picture the tie back straps — long metal strips that will be attached to the backs of the blocks.

The process is to lift the cement panel into place, sliding it into the slots, grooves, and dowels of its neighbours. The panels are temporarily clamped together for support. Then the inside is filled with crushed rock that gets compacted.

The stone can be added right up to the wall. The piers are completely encircled with rock to minimize any sideways pressure on those columns.

Black landscaper’s cloth is added to prevent any fine material from being washed out through the joints.

You will, no doubt, notice the many metal tie-points on each of the wall sections. These are for attaching straps that will be secured as ‘tie-backs’; preventing the wall from bulging out. The ‘old’ viaduct had such straps, which can still be seen at the edge of the new construction. The tie running toward the viewer,  highlighted in the following inset photo,  is no longer tight, but still connects to the old wall segment.

The weight and friction of the compacted gravel onto the tie back strips is what prevents the concrete wall pieces from tumbling over.

Apparently the same style of wall cladding will be used at both the west and east abutments, but the west uses metal tie back strips, and the east will use flexible tie backs.  If two different anchoring systems are being used, it will be interesting to see if one lasts better than the other. Remember, RTG is responsible for maintenance on the Confederation line for 30 years.

next: the east side abutment walls

— Richard Eade