M4 Junction 13
Working with design and build contractor Costain Civil
Engineering, Mott MacDonald was appointed as designer for the A34
Chieveley improvement scheme – developed to alleviate major
congestion and so improve safety at the interchange of the M4 and
A34 Junction 13.
We carried out the detailed design of ten bridges. The new junction
13 required three adjacent bridges to allow the M4 and the parallel
east and westbound sliproads to cross the line of the new A34.
These were constructed whilst keeping three lanes of traffic moving
in each direction on the M4. Three successive phases of traffic
management allowed construction of one third of the M4 bridge at a
time in a top-down sequence. Working from the M4 carriageway level,
contiguous bored piles were installed to form the bridge abutments,
then precast deck beams were craned in after which the bridge deck
was concreted and surfaced. Thereafter, excavation proceeded
beneath the live traffic.
The existing J13 roundabout is retained with four
new highway bridges carrying the sliproads linking to the new A34.
There is also one other highway bridge and two equestrian bridges.
The highway bridges and one equestrian bridge –111m long with three
spans – are steel composite designs, whilst the other equestrian
bridge is a single span truss erected over the M4 during a limited
closure. Ladder deck steelwork systems were used on the sliproad
bridges: two 4 span bridges over the A34, and two 3 span bridges
over Bird Lane, the latter being integral bridges with embedded
abutments. The other highway bridge has a multiple girder steelwork
system and contiguous pile wall abutments.
