Confined spaces To maintain efficiency, it is important that high-output trains can continue to operate alongside station platforms, over bridges and past obstacles without being seriously affected by the reduced clearances. The PM1000 URM and RU 800 S are both able to do just that by adjusting the working width of excavating chains and plate compactors. The RU 800 S, in particular, has independently controllable shoulder ploughs to enable it to work close to station platforms. This ability was tested at Dollern station, which has platforms only 76cm high and is on a curve. Recycling ballast Ballast is heavy, and is therefore expensive to transport any distance. To keep the use of new ballast to a minimum, the Plasser & Theurer PM 1000 URM was used to both clean and recycle ballast. Depending on the quality of the existing track bed, up to 100 per cent of the ballast could be reused. It was also often not necessary to use geotextiles because, after compaction, the 30-centimetre-thick formation protective layer alone met the load- bearing specification. Any spoil that was not able to be recycled was to be taken away by material conveyor and hopper wagons (MFS) and deposited temporarily beside the line in Horneburg. With three excavating chains, the PM 1000 URM is both quick and efficient in excavating existing ballast to any required width and depth. Excavated material is first moved to the ballast recycling, screening and washing wagon. Any resultant spoil for disposal is conveyed on belts to the construction train of MFS units coupled on to the front. Fresh material, both for the formation protective layer and to top up the ballast, is transported to site using a second construction train, this one consisting of transport wagons with containers rather than MFS units. From this train, new ballast is fed to the rear of the 52-axle, ten-unit PM 1000 URM. Both construction trains travel independently to and from disposal and loading sites along the line. To shorten the distances, a storage area for new material was established at Dollern level crossing, which was under possession anyway. Here, a wheeled loader filled the containers with ballast. On arrival back at the PM 1000 URM, containers were transported along the length of the construction train using two gantry units running on the transport wagons. The outer gantry continually fetched two containers whilst the second gantry unit, running closer to the machine, tipped one container-load at a time into its bunker. This relay system, with containers being handed over partway along the train, shortened the travelling distance for both gantry units, their paths crossing only at the handover point, speeding-up operations. Once the formation protective layer and ballast had been laid, and the track returned to position, an integrated tamping unit, with lifting and lining facilities, concluded this first phase of operation. The track was now usable by construction trains. Overall, the PM 1000 URM was able to achieve a considerable work output. Over the Easter weekend, in around 50 hours of continuous operation, it completed a section of almost 5,000 metres at Dollern. Replacing rails and sleepers The second stage of the process was to remove the old, temporarily relaid, track and replace it with new rails and sleepers. New rails had already been laid along the edge of the existing sleepers. An RU 800 S from Plasser & Theurer carried out the track replacement in a single operation. Using an array of clamps and rollers, the old rail was lifted from the sleepers and guided out to the edge of the trackbed. Simultaneously, the new rails, previously laid alongside the old sleepers, were picked up and guided inwards. Although this process requires the rails, both old and new, to be flexed both upwards and sideways, this takes place over a 45-metre length so no permanent distortion occurs. Simultaneously, the old sleepers were lifted automatically by a conveyor and taken up into the machine, to be replaced by new sleepers brought in from the attached construction train by gantries, 30 sleepers at a time. The gantries then returned the old sleepers to the space on the train vacated by the new ones. Top ballast, excavated after the old sleepers were removed and stored temporarily in a hopper in the machine, was replaced and topped up where necessary by new ballast supplied continuously from MFS units coupled to the other end of the machine. Final alignment and tamping Once the ballast had been cleaned and the sleepers and rails had been replaced, the track had to be brought back to its nominal geometry. A 09- 4X dynamic high-speed tamper with four-sleeper tamping and dynamic track stabiliser was used to achieve this. Being able to tamp four sleepers at a time, and using the continuous working method described in Geoff Brown’s article elsewhere in this issue, allowed the track to be aligned at a comparatively high speed. Another construction train of ballast wagons followed behind, using the BDS 2000 ballast management system to ensure ballast only went where it was needed and wasn’t wasted in the cess. Shoulder ploughs and a central plough, plus sweeper units in the rear section, removed superfluous ballast after the tamping operation and re-distributed it or temporarily stored it in a bunker. An MFS wagon was added to the BDS 2000 to increase capacity. Satellite measurement An EM-Sat 120 track survey car was used, between the high-speed tamper and the BDS 2000, to record track geometry. This electronic surveying unit records the lateral, longitudinal and vertical geometry of the track. To do this, a small self-propelled trolley moves forward and then pauses. The main machine then moves towards it and, using laser sensors across the space between the two vehicles, the level and alignment of the track can be determined. The results are recorded on eight-channel recorders, and all measured values are stored digitally. MFS advantages The amount of materials used in the project necessitated the use of numerous material conveyor and hopper wagons. Both when supplying material and removing spoil, their ability to convey the load from one end of the train to the other was crucial. Using the conveyors, spoil could be deposited directly at a disposal site next to the track for subsequent removal. On return to the construction site, the conveyors could carry fresh material directly to the hoppers in the machine. If an MFS train was withdrawn for emptying or loading, several MFS wagons remained attached to the construction machine in order to avoid any stoppages. These dedicated wagons were then filled back up once fresh supplies had been brought to site, again using the on-board conveyor system. Facts and figures Working on one track at a time, the machinery used at this worksite, some of which was unique, moved a total of 10,000 tonnes of new ballast. 11,800 tonnes of spoil was removed, and a far greater amount of ballast cleaned and returned. The formation protective layer required 3,500 tonnes of new material. For the track itself, 10,800 new concrete sleepers and 13,120 metres of S54 rail were installed and a similar quantity removed for recycling. Using these construction methods, it was possible to work without interruption even through the platforms of Dollern station and over the few culverts under the line. The whole project took 27 working days and, after a gap of several weeks, another three nights for the final re-tamping. Written by Achim Uhlenhut
There is to be a full 8-car electric service between Edinburgh and Glasgow in July offering 27 per cent more seats.