The October update on progress towards the A46 Stoneleigh Junction Improvement Scheme.
Overview
Throughout September, construction work has taken place in several areas across the site, particularly the A46 Bridge, Dalehouse Lane Roundabout, Northbound Off Slip, as well as Stoneleigh Road East and West. Presently there is still a 50-mph speed limit being enforced on the A46 mainline to allow safe working during the construction process. Crucially, this is an aspect of traffic management which will remain in place for the foreseeable future. Furthermore, a 30mph speed limit is operating on Stoneleigh Road, which runs for the entire site extent. At the start of the month, HS2 lifted their Stoneleigh Road East closure, allowing for the new traffic management arrangement of Stoneleigh Rd and the Southbound Off and On Slips to come into effect. Consequently, this has resulted in traffic heading towards Stoneleigh from the slip roads travelling two-way on the new road alignment with traffic management and temporary road markings in place to assist users.
Progress to date
Northbound off slip realignment works
Work has progressed in the month with regards to constructing the Northbound Off Slip. Previously, one lane of the slip road had been completed and opened to traffic, which was an important step in allowing for work to progress on the second lane, maintenance layby, drainage and ducting. The work to these elements is now largely complete and Figure 1 below shows base and binder surfacing has been laid with only 40mm of the final surface course now required.
Figure 1 - Northbound off slip and maintenance bay
Westley Bridge
As shown in Figure 2 below, work has continued to install and seal the permanent formwork panels, which initially commenced in early July. These panels are situated between the bridge beams; ultimately forming the first part of the main bridge deck and will be visible from underneath. Importantly, each panel needs to be individually lifted using a crane and guided into place to ensure a tight fit with both the bridge beams and neighbouring panels which is a very time-consuming process. Each panel also needs to be sealed against the bridge beams and the neighbouring panel.
Furthermore, work commenced with installing deck and diaphragm reinforcement. This is the final stage of the structure. The diaphragm “links” the deck to the abutment and foundations of the bridge that have been constructed previously.
In addition, a headwall has been constructed which feeds from the bridges’ back of wall drainage. The back of wall drainage is crucial to bridge construction as it mitigates water pressure building on the retaining wall of the bridge.
Figure 2 – Westley Bridge panels and reinforcement
New Dalehouse Lane roundabout
Previously, the Himalayan Balsam contaminated material has been installed in a central mound of the new roundabout and this will be a permanent feature. The mound has been constructed with a geotextile fabric to contain the contaminated material and finally topsoiled. In the future, the topsoiled will be seeded. This can be seen in Figure 3 below.
The kerbing of the central island started in August using Duradrain Recycled Plastic Kerbs was finished in the period. Additionally, all the drainage and ducting works have been installed within the central island. The capping (which forms the first part of the road foundation) around the inner radius of the roundabout is complete and following this Type 1 material has been installed on top in the next stage of the road construction.
Figure 3 - New Dalehouse roundabout progress
New Dalehouse Lane link road
The new link road will eventually realign Dalehouse Lane to meet with the roundabout currently under construction and detailed in the previous section. During September, the main part of the carriageway construction was completed following surfacing operations. The tie-in point with the existing Dalehouse Lane has now begun with kerbing and drainage works being carried out during a temporary lane closure. The new footway has now also largely been completed, with surfacing laid simultaneously to the tie in works mentioned above. The status of the new Link Road can be seen in Figure 4 below.
Figure 4 - New Dalehouse Lane link road resurfacing
New A46 bridge
During this month, work has been underway to construct the concrete base for the back of wall drainage pipe required for both abutments. Following this the area was then backfilled up to the predesigned level with 6N backfill material and a general backfill layer in order to remove temporary sheet piles which were previously a vital tool used to retain the earthworks around the abutments. Additionally, catchpit and drainage diversion works have taken place. The bridge girders have been jacked to the design profile to prepare for future cut and reweld operations.
Figures 5 and 6 show the progress of the works to the two abutments.
Figure 5 - concrete base and backfilling operation
Figure 6 - East and west bridge abutments
Existing A46 bridge
The south footway on the existing A46 Bridge has been closed whilst work is underway to expose and remove a redundant gas main from the service bay. At the same time the layer of waterproofing was removed and will be replaced with a new version. This can be seen in Figure 7 and this trough will remain open whilst new lids to cover them will be fabricated.
Figure 7 - removal of gas main
Stoneleigh Road East tie in
During early September the new temporary traffic management layout opened to vehicles along sections of the carriageway on Stoneleigh Road East. This happened following completion of the tie in, which connects to the existing Stoneleigh Road and carriageway surfacing. The current layout will now be in place for the foreseeable future and allows access to Stoneleigh, Kenilworth and the A46 mainline. Some examples of the new road arrangement can be seen in Figures 8 and 9.
Figure 8 - carriageway surfacing and new kerb line for Stoneleigh Road East (towards Stoneleigh Village)
Figure 9 - carriageway surfacing and new kerb line for Stoneleigh Road East (towards new roundabout)
Further information
Looking ahead work will continue with respect to the Dalehouse Lane roundabout, in order to finalise the road through applying surfacing layers to complete the carriageway construction. The remaining three roundabout arms will be formed over the coming months. Following installation of the permanent formwork panels at Westley Bridge, the concrete deck pour is projected to commence in the near future. After this process the road box cut on each side will be excavated eventually lending itself to start road construction across the bridge.
The project is entering its final phases where various tie ins to existing roads will be conducted. This means that the traffic flow through the site will be changing periodically. It is intended to close the existing A46 Bridge towards the end of October to facilitate repair work and waterproofing. Following this, closures of Stoneleigh Rd West outside of Brook Farm and Dalehouse Lane (although not at the same time) are intended to allow the tie in work between the existing road and new roads to take place.
As a note for all road user’s diversion routes will be implemented and signed for all closures.
It is also expected that work to the new A46 Bridge Deck will be completed in the next two months and the deck will be moved into position towards the end of the year.