Aberdeen to Inverurie Redoubling Inc Don Viaduct
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Aberdeen to Inverurie redoubling inc Don Viaduct AUTHOR ABSTRACT • Forres – new twin platform station with 1300m passing loop allowing simultaneous arrival in to the station. One new overbridge Robert McCafferty Aberdeen, population 200,000, is Scotland’s third and one new underbridge installed. Two LX’s Technical Head of largest city. Inverness is one of Europe’s fastest closed and two UWC’s upgraded. Closure Track, BAM Nuttall growing cities. Linking them is the Aberdeen to of Forres signal box and removal of token Inverness line, 107 miles of mostly single line exchange signalling system. New signalling Robert started on the railway with eight additional stations spread along system recontrolled to Inverness SC. railway in December the route, each with their own passing loop. 1995, spending his first After completion of the works on the west, six years working with Until 2019 the line carried 11 trains from attention turned to the eastern end of the line. Scott Wilson Railways Aberdeen to Inverness per day and the same on This section of line was the busiest on the whole in Glasgow. The six years were spent in a the return, with the journey averaging two hours route, allowing passengers to travel between survey and design environment and gave 18 minutes. An additional 15 commuter services Aberdeen, Dyce (Aberdeen airport) and the town Robert the foundations for the years and roles ran between Aberdeen and Inverurie and two of Inverurie. Due to a pressing need for increased to come. Six years followed with Mowlem between Inverness and Elgin per day. The journey commuter services at the eastern end of the line, Railways on the contractor side, followed by times and irregular service between Aberdeen emphasis had been placed on this section for three and a half years with Network Rail. and Inverness meant that the railway line did not the greatest extent of proposed redoubling. In offer an attractive alternative to road travel. addition a new station was proposed at the town Robert moved to Australia, spending two of Kintore. years in Brisbane with AECOM. Since As part of a strategic review carried out by returning in 2013, Robert has worked in Transport Scotland in 2008 a set of key output The existing line from Aberdeen to Inverurie was various CRE and CEM roles and is now the requirements were established for the Aberdeen 16.25 miles of single line, with a 0.75 mile section Technical Head of Track for BAM Nuttall. to Inverness line: of double track serving Dyce Station and Raiths Farm freight facility. The proposal to redouble Robert is currently working towards CEng • hourly service between Aberdeen and this section of line was made more complicated status through the PWI Experiential Learning Inverness because since the line was singled in the 1960s, Route. • half hourly service between Inverness and the existing track had gradually been renewed Elgin including a new station at Dalcross and maintained to follow the racing line in six • half hourly service between Aberdeen and areas (see image 4), removing clearance issues Inverurie including a new station at Kintore through overbridges, platforms and a tunnel (see • a circa two hour end to end journey time image 5). • maintain, as a minimum, the ability to deliver existing freight access rights on the route. In addition large sections of the existing single line had track components not suitable for a Achieving these outputs would require a series of linespeed increase. This meant that a scheme interventions to be carried out along the length of to redouble 17 miles between Aberdeen and the route. Inverurie, resulted in 60% of the existing line having to be renewed. WESTERN INTERVENTIONS Over a period of 18 months, AECOM, Jacobs Over the course of 2015, 2016 and 2017, and Siemens designed the works required for the interventions at Forres and Elgin on the western redoubling, with the output being: end of the route were designed and constructed. At completion the following works had been • 40,000 m of new track including 15 new delivered: point ends • 85,000 m3 of earthworks • Elgin – extension of existing platforms. • 4,300 m of retaining walls Extension of existing loop from 630 m to • 30 structures altered (extensions, infill, 1330 m including new F21.5 turnouts at removal, strengthening) either end allowing simultaneous arrival in • 3 level crossing removals, 3 upgrades. to the station. Upgrade of Elgin LX (level • new station at Kintore crossing) to MCB-CCTV. Closure of Elgin • plus re-signalling throughout along with signal box and removal of token exchange associated ancillary civils, resulting in signalling system. New signalling system the closure of signal boxes at Dyce and recontrolled to Inverness Signalling Centre. Inverurie Image 1: Aberdeen to Inverness line diagram. 20 Image 2: Forres Station area - 2015. Image 3: Forres Station – December 2017. Image 4: Aberdeen to Inverurie redoubling - existing layout. Image 6: View towards Aberdeen from 2 m 1715 yds. Image 5: Track centred through OB51 Blackburn Road. Image 7: Kittybrewster scheme plan extract. 21 Image 8: Don Viaduct superstructure. Image 10: Proposed substructure works - initial option. Image 9: Don Viaduct substructure. These works would be carried out during 2019 BLOCKADE - DON VIADUCT a series of rules of the route possessions, weekend possessions (54 or 78hrs) and a 14 As part of the 2019 blockade, Don Viaduct, week blockade in each of the summers of 2018 a 103 m long, five span viaduct was to be and 2019. upgraded to carry a second track. The viaduct carried the existing single track on waybeams 2018 BLOCKADE - ABERDEEN over the river Don and its floodplain. The rail TO DYCE bearers span between cross girders supported from 2 outer main girders on a skew angle of The 2018 blockade primarily consisted of 35 degrees. It was recently strengthened and works between Aberdeen and Dyce. During repainted but only for single track loading. the 14 weeks, all earthworks, structures work, There is no deck, apart from an open mesh drainage, ancillary civils and trackworks walkway. Therefore the deck is relatively were completed. During the initial part of the lightweight (see image 8). The superstructure blockade, all the existing track was removed is supported by eight 2.1 m diameter granite other than two short sections that only required masonry piers and two granite masonry tamping. This allowed the site to be managed abutments (see image 9). as a high street environment, reducing the need for expensive rail mounted plant and DON VIADUCT - INITIAL OPTION allowing earthworks and drainage to be WITH BALLASTED BRIDGE Image 11: Output from seismic ground completed quicker (see image 6). DECK penetration. By the end of the blockade, the existing single At early GRIP (Governance for Railway line had been lifted, slued and renewed to Investment Projects) stages it was established form the down line. Four miles of the new that the superstructure could be strengthened up line had been laid, but not connected to support a second track. Several options at either end and the Kittybrewster sidings including complete replacement and various area installed to a temporary alignment that strengthening schemes were considered. maximised the amount of the new layout that Key to this was removing the waybeams and could be installed, whilst still retaining the installing ballasted track. The existing cross existing signalling and functionality. Image 7 girders needed significant strengthening, below shows an extract from the Kittybrewster so to simplify construction these would be Scheme Plan at the end of the 2018 blockade. removed and replaced with heavier sections. Black = existing, red = new track brought in to The main girders needed some straightforward use, blue = new track not brought in to use. strengthening, and a new steel deck, ballasted Image 12: Shock transmission units. track and cantilevered walkway would be 22 Image 13: History of cross girder detail. The group looked at ways of reducing the deadload by investigating a waybeam solution, removing the weight of ballast and steel deck plates. Using a risk-based assessment, AECOM compared historic loading against new loading to determine the reduction in factor of safety. If the factor of safety could be shown to be close to historic cases, the technical solution proposed could be shown to be feasible. For waybeams, AECOM calculated that the vertical loads only imposed a marginal reduction on the FOS (Factor of Safety). However, the longitudinal traction and braking loads meant that substructure strengthening was still required. Image 14: Typical detail of waybeam and BRC7 baseplate. Piling in the river was still the key constraint to installed. the programme so AECOM proposed the use AECOM found that we would need to install the of shock transmission units (see image 12). Proposed superstructure solution: concrete collar with piles anchored into rock The shock transmission units lock up when level for the design to work. This would have a longitudinal loading is applied transferring the • replace cross girders significant impact: load through the structure into new transition • 85 new cross girders / trimmers slabs behind the abutments. By doing this the • 164 new stiffeners • access to install piling would impede the longitudinal loading was taken out of the piers, • strengthening of main girders installation of the scaffold needed to carry and AECOM were able to demonstrate that the • new cantilever walkway out steelwork strengthening FOS were the same or better than the historic • the piling and steelwork strengthening case. This solution took the piling out of the In order to support the increased dead load of would all have to be carried out in the river clearing the way for the superstructure the deck, substructure strengthening would be blockade.