The November update on progress towards the A46 Stoneleigh Junction Improvement Scheme.
Overview
During the course of October, a range of construction work has been undertaken on site. Most notably, the road construction to the new northbound on-slip and southbound off-slip has been making significant progress – in particular the kerbing and road foundation construction. The progress will allow the construction of the pavement tarmac surfacing which we hope to start in early November on the northbound on-slip.
The earthworks fill operation has been continuing and is now alongside the existing Dalehouse Lane roundabout and will be the future site of the new Dalehouse Lane roundabout. Work has also commenced in laying the ducting which will form part of the future electrical connections for street lighting and permanent traffic signals.
Progress to Date
Westley Bridge Cofferdam
Throughout the month, work has continued installing a temporary cofferdam on the north side of Finham Brook.
The cofferdam has been built to facilitate working below ground level and helps to support the surrounding ground to ensure it does not fall into the excavation. This process involved inserting sheet piles, prop bracing (to hold the sheet piles in place vertically) and excavating out around the previously installed piles within cofferdam. Sheet piles are rigid and do not bend under pressure from the surrounding ground (and groundwater) and ensure the excavation stays in place.
The ground surrounding the piles needs to be excavated to allow the erection of formwork which will allow the concrete of the reinforced concrete beam (known as the pile cap) to be cast, thereby linking the individual piles into one structure. This pile cap will then have the abutment built on top of it and will eventually result with the new bridge beams resting on them. The beams will eventually form the new road surface that the public will drive on.
The ground around four piles has successfully been cleared with an additional eight still to be finished prior to the casting of the pile cap. Following the excavation work, concrete will be poured before cropping the piles to the correct level and allow subsequent construction of the pile caps. The cofferdam arrangement can be seen in Figures 1 and 2.
Narrow Lane Running
The narrow lanes on the A46 installed in early September remained in place throughout October to maintain safe working conditions whilst construction work is undertaken on the mainline carriageways. The ongoing 50-mph speed limit and associated traffic management will be in operation for the next few months, and this will be supplemented by the ANPR speed enforcement cameras.
Installation of Kerbing
In October, work significantly increased in installing the permanent kerbing that forms the edge of the carriageway on Stoneleigh Road East; northbound on-slip; southbound off slip and the new roundabout gyratory (both east and west sides). Some examples of the installed kerbing can be seen in Figures 3, 4 and 5. By the end of November all of the kerbing and tie-in points on the northbound and southbound on and off-slips will be completed in preparation for transferring the traffic from the existing network to the new. This will facilitate a safe working area for the new A46 Bridge to be constructed.
The kerbing installed is largely a combined kerb drain system. This has holes cut in the front to allow the ingress of surface rainwater into the hollow body of the kerb itself. A line of kerbs forms a “pipe” which then allows the water to drain to regularly placed kerb drain outfalls which connect into the main drainage system.
Further Information
Construction work will continue Westley Bridge including further excavations and concrete pours within the sheeted cofferdam on the north side of Finham Brook. On the south side, work will commence on a second cofferdam.
The earthworks fill process will continue, with a particular focus on raising the ground level in the surrounding area of the new Dalehouse Lane roundabout.
The main focus for November will be for the tarmac surfacing to commence, with work initially starting on the northbound on-slip before progressing onto the southbound off-slip. Night closures are planned for the northbound A46 carriageway in order for works to be carried out. It is hoped that these works will permit the opening of at least the new northbound on-slip road by the end of the month.