Clearing the road to the future
By Lindsay Gale14 May 2012
As part of the ongoing dual carriageway trunk road upgrade to motorway standard of the A1 between Dishforth and Leeming Bar; Tyne Tees Demolition were appointed by Carillion Morgan Sindall, on behalf of the Highways Agency, to carry out the demolition of structures and road side buildings in various locations along the 23 km (14.3 mile) site. The road-side buildings, consisting of houses, farms, cafes and petrol filling stations, were demolished early in the project between August 2009 and February 2010.
Between June 2010 and June 2011 seven structures were demolished, each presenting its own set of challenges to be overcome.
The project required two lanes of traffic in north and south directions to run at all times, resulting in complex traffic management schemes including temporary roads, narrow lanes and diversions; however full A1 closures were required to demolish the over bridges, with these being planned and implemented by the main contractor. This meant that the demolition works were either carried out in very close proximity to live traffic or during overnight weekend closures requiring highly detailed planning and management to carry out the works safely. Further constraints were placed upon Tyne Tees Demolition due to the environmental sensitivity of the site. Nesting birds, newts, badgers, bats and various other species had come to call the area home. Mitigation was carried out jointly by Tyne Tees Demolition, the main contractor and other sub-contractors on site. The proximity of habitats reduced working space on many of the structures to be demolished and required additional planning and management to ensure that the works did not interfere with the surrounding environment in any way.
Leases over bridge
The Leases over bridge consisted of a slender concrete deck supported by five plate girders spanning the 31 m (102 ft) wide trunk road with a reinforced concrete abutment to each end. The bridge was planned to be demolished over three 18 hour closures of the A1with the concrete deck and beams first to be removed then the east and west abutments. During each of the three demolition stages, the carriageway was to be protected, the debris removed and the A1 reopened on time. The solution was to plan every detail meticulously and ensure that nothing was left to chance. The need for contingency was a high priority of the management team - additional machines and equipment were brought to site and overnight maintenance cover put in place in case of a breakdown. Fifty tonne excavators with hydraulic breakers were used to break out the deck from above, Stress simulation software was used to estimate the stresses placed on the beams during demolition and to determine a safe sequence of demolition. To avoid over-stressing the beams, the deck was broken out in alternate quarters with the sequence plotted using 2D CAD in a format that could be understood by all involved, from client to site operative.
On successful removal of the deck, a 500 tonne crane was used to remove the five beams. The clear up operation could then begin removing redundant reinforcing steel and concrete debris from the carriageway to the stockpile offline. The abutments were then demolished during the subsequent closures.
Butcher House underbridge
Butcher House under bridge carried the A1 over the 12 m (39.4 ft) wide B6267 at Sinderby. The bridge was constructed from 12 steel girders supporting a concrete deck with a secondary deck cast on top of the original to meet regulations in 1998. The B6267 was closed for 10 days to allow demolition to be carried out, with extensive planning being required to overcome the specific challenges presented by this structure. The main challenge was that the existing structure was situated only 600 mm from the newly constructed bridge now carrying live A1 traffic. To carry out the demolition the tarmac deck was planed off and the planings used to protect the B6267 beneath. The concrete deck was then demolished in two halves to maintain access for the excavators and stability of the remaining structure. The beams were removed in turn using excavators and propane cutting equipment. The bank seats were broken out on completion of the deck removal and the road reopened three days early. All this work was carried out during January 2011 working night shifts in adverse weather conditions.
Sinderby Rail Bridge
This former London and North Eastern Railway (LNER) railway bridge situated 100 m (328 ft) north from Butcher House Bridge was to be demolished next, again within very close proximity to the live A1. The bridge consisted of mixed construction partially similar to Butcher House Bridge and partially pre-stressed concrete beams supporting a slender concrete deck, with these pre-stressed concrete beams being some of the first used in the UK. The void beneath the bridge had been pneumatically filled previously, which reduced the complexity of demolition. The bridge was demolished in two halves to enable traffic to run with minimum disruption.
This bridge was identical to Leases Bridge, and demolition was carried out successfully and the A1 re-opened two hours ahead of schedule.
Of similar in construction to that of Leases over bridge, the demolition of Cowfold bridge was carried out offline but due to earlier works carried out on the east abutment to remove the wing walls to allow the new northbound carriageway to be constructed, the structure was deemed insufficiently stable to demolish using the same method. Under closure, due to the close proximity of the new carriageway, the deck had to be demolished from ground level using high reach equipment. This reduced the effectiveness of the equipment and resulted in many more hours of work. The deck was broken off within the closure and the beams removed the following week. The abutments were demolished under subsequent closures as Leases over bridge.
Farwood Bridge carried the existing A1 over the Bedale River and was to be partially demolished to create the new Local Access Road. In order to reduce future maintenance the Client required the removal of 7.2 m (23.6 ft)width of bridge deck and four steel beams. The main challenge was that the river below was an environmentally sensitive area and as a result a crash deck and complex system of drainage channels had to be constructed underneath it to allow the sections to be cut free and removed. The bridge deck was cut using diamond cutting blades and removed in two sections using a 700 tonne crane to remove two beams and a section of concrete deck in each lift of approximately 40 tonnes.
Due to lifting regulations temporary supports were installed to the underside of the beams to allow the deck sections to be released from the crane if required. The removed sections of deck were broken up by excavators and hydraulic breakers adjacent to the bridge.
The Aiskew bridge removal was a similar project to that of Farwood bridge but in this case was situated over the A684 at Leeming Bar. For this reason the same demolition method as Leases bridge was used to demolish 4.5 m (14.8ft) of the existing structure. The works were completed and the A684 opened by the main contractor 22 hours ahead of schedule.
100% of the debris created by this demolition project was recycled, with the majority being crushed on site and re-used for road formation. This project displayed the capabilities of Tyne Tees Demolition to plan, design, execute and manage all the tasks required in such a complex demolition project. Client feedback was excellent from the project; emphasis was made on the organisation's capabilities to fit in with the client's programme and its "can do" positive attitude. The demolition works were completed 100% accident free.