west portal of the Tesco
tunnel will be the only part of the structure in full public view, and
will be a prominent feature as seen from the station platforms and
Much preliminary work was done in this area in 2004 and 2005 until it was brought to an abrupt halt by the tunnel collapse on June 30 2005. In fact, some important work was done between the collapse and the re-opening of the tunnel and railway in August that year. An account of that work has been on-line here previously but it is now available again by clicking on the picture left below which is how the site looked in 2005/6.
temporary structure which enabled all the work under the bridge to be
done was removed in late 2006. Work was done to stabilise the
cutting slope in March 2007 by equipment, seen below, which was lifted
over the railway from the north to the south side by a large crane.
on the north side illustrates nicely that the 2-track railway only
occupies half the tunnel, although if it was ever enhanced to 4 tracks
with electric catenary and continental loading gauge stock, the tunnel
could handle it. The ground has been prepared for the placement
of a steel structure to support the additional tunnel arch segments.
segment is now in position, supported by the steel frame. The
stainless steel hinge plate awaits its meeting with another segment
placed on the south side.
segment on the south side is now in place. It is resting on
foundations created in 2004/5 but has itself been modified, probably to
provide more steel loops for interlacing with the ground
foundations. We are now in early May 2009.
The next stage was to create the tunnel portal itself with its impressive curvature. But first another supporting steel frame is needed and this colourful framework appeared. It had to cover the entire railway to support the concrete pieces and provide access for the men working on it.
The steel frame now spans the railway and is ready for the shaped pieces to be placed on it. In the meantime on the crown of the tunnel to the right, temporary red steel beams are being secured to the concrete segments. With the addition of more beams at angles, the steelwork will ensure that the north and south sides of the tunnel do not move relative to each other. This was not done in the original construction but it has been for the full length of the tunnel during reconstruction.
The first of the shaped pieces is in place together with its unseen equivalent on the north side.
Most of the shaped pieces have been placed. Unlike the tunnel segments they cannot be self-supporting so they are strongly anchored at ground level and will finally be held by the reinforced curved beam which we will see later.
The three dimensional curvature of the portal is well displayed here.
At this stage, debonding material has been fixed to the outside of the tunnel segments and a base created in preparation for the building of the new tunnel structure over the top of the original segments.
This picture has rather a lot going on! The tunnel segments on the right now are encased in curved reinforcing steel and ready for concrete to be poured into the curved shuttering. Exactly the same applies to the north side.
On the left, access scaffolding, safety fencing and access platforms are in place. In an earlier picture we can see the ground level anchorage, but now it is all encased in concrete. The crane has changed too, now being lighter but with a very long reach. The date is mid-September 2009.
This gracefully curved reinforcing steel will soon disappear into the concrete ring beam that will form the visible part of the tunnel portal.
The ring beam is now complete, although still surrounded by steel supports and woodwork, but it is entirely self supporting. It is now early November 2009.
Late November and the west portal stands clear of most of its clutter.
It was not long before more safety fences and other new clutter was put in place, for there is still much to do before the space between the portal and the bridge behind it is filled and shaped ground created to the north and south in the present cutting.
the TescoTunnel home page here.
Pictures and text © Guy Gorton 2010