The February update on progress towards the A46 Stoneleigh Junction Improvement Scheme.
Overview
Since the start of the new year, construction work has been focussing on a number of key areas, specifically the southbound off-slip, eastern gyratory and the new A46 and Westley Bridges. Additionally, to create a new embankment to the northbound off-slip, we have imported new earthworks fill.
Two balancing ponds have been dug alongside the existing Stoneleigh Road which will be a part of the road drainage strategy one of these can be seen in Figure 1. They will have a dual purpose, as the proposed planting will ensure they also provide a valuable habitat. The swales and balancing ponds will be seeded with mixes that include native wildflowers which grow well in wetter conditions. Common reed will be planted in the ponds, which acts as a natural filter, removing pollutants and oxygenating the water. Marginal plants and reeds provide important habitats for a wide range of birds, mammals, insects and amphibians. Oxygenating plants will also be planted in the ponds which will help keep the water clear and clean, limit the spread of unwanted algae, and allow other forms of pond life to exist.
Construction has continued on the southbound tie in, in particular completing works to relocate a chamber and install new kerbing. Elsewhere across the site, work has been continuing to lay new drainage and electrical ducting.
Progress to date
Northbound off slip embankment works
The work to construct the new embankment alongside the existing northbound off -slip is continuing and is nearing completion. This is to allow the realignment of the slip road to better join into the new gyratory safely. The imported material is installed in layers which are then compacted using a roller to ensure it is a solid mass and stable.The progress of the installation is shown in Figure 2.
Westley Bridge
In previous periods, the work to construct the new pile caps to both sides of the bridges has been completed. Bituminous paint has now been applied to the pile cap on both sides as a layer of waterproofing as, ultimately, the pile cap will be buried below ground in the finished state. This period, work has begun to backfill around the pile cap which is necessary to ensure the surrounding ground interacts with the bridge structure in a controlled manner and not result in differential settlement between the structure and/or the road.
Work is continuing the construction of the abutments, by fixing a grillage of steel reinforcement, followed by erection of vertical formwork and a concrete pour. Abutments are concrete seats upon which the bridge beams can be supported at each end of the bridge. Once this stage is complete, the temporary shutters will be removed and all exposed surfaces will be treated to make them waterproof. As an extra feature, a drain will be laid behind the abutments, with a granular fill implemented to road formation level.
The progress for the bridges can be seen in Figures 3 and 4.
Eastern Gyratory
Footpath construction has started on the eastern gyratory and Stoneleigh Road East. This involves laying new concrete edges (which form the back of the footpath) and then preparing the footway foundation by laying and compacting subbase.In the future, the footway will be surfaced with tarmac to the finished arrangement. The ongoing work can be seen in Figure 5 below.
New A46 Bridge
In the period, work has progressed on the deck of the new A46 Bridge in terms of installing the permeant formwork for the bridge deck as can be seen in Figure 6. This formwork allows for the future installation of the concrete deck to the bridge on which the road will be placed.
Previously, a cofferdam excavation was constructed for the new west abutment to the bridge. After a check of the condition of the ground in the excavation, a blinding layer of concrete has been poured to create a solid base. This is the first part of constructing the new bridge foundation on the west side. The blinding concrete in the cofferdam can be seen in Figure 7. Assembly of the foundation reinforcement steel cage will start shortly, followed by a concrete pour for the actual foundation.
Further information
Going forward, overnight closures to parts of the A46 mainline are planned to take place between 8pm and 6am from the 31 January to the 6 February 2022. These are required to offer a safe working area when the final work to construct the new southbound off-slip tie-in (to the mainline A46) is conducted). It is planned to have the new slip road open by early February 2022, at which time the existing southbound off-slip will be decommissioned. This will enable the next critical aspect of work to commence which is the construction of the new A46 bridge foundation on the east side.