Asia
The Shuo Huang Railway carried 234 million tonnes of coal in 2012 and is aiming to increase this to 400-600 million by 2018-2021.
Ballast: on bridges, culverts and tunnels where ballast depth is less than 200mm compared with up to 800mm on approaches, longitudinal stiffness is no longer uniform so increasing axleloads will reduce track lateral stability, worsen track geometry and result in an
increase in sleeper failures. Turnouts: increasing axleloads to over 30 tonnes will result in an increase in turnout failures, which currently have a service life of 80-250 million
gross-tonnes. Bridges and culverts: at 30-tonne axleloads the operational loads will exceed the design load for all span range bridges and culverts, and exceed the load for small bridges and some medium and longer span bridges by 20% depending on the length of the
train. Tunnels: minor leakage problems have been reported but these have been repaired and overall these structures are generally in good condition. However, increasing axleloads could result in problems with the tunnel bed and with inverted arches, problems with the supporting rock capacity due to
additional stress. Subgrade: the line suffers from several sections of poor geological
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conditions and has shown gradual deterioration as traffic has increased. A remedy programme has though been successful and this would have to be repeated if axleloads are increased. These findings subsequently led to a
comprehensive testing programme carried out with the support of Transportation Technology Centre Inc (TTCI), United States. A 43.4km test section with a maximum gradient of 1.2% was used which included 19 curves with a radius of between 500 and 1000m, most types of bridges and culverts, three tunnels, and different types of subgrade. Two steel truss bridges and one continuous pre-stressed concrete bridge were also tested beyond this section using a 25-tonne axleload train, while static tests and the use of two strengthening techniques were carried out on a 32m-span T-beam bridge.
The train used for line tests consisted of 10 C80 25-tonne axleload wagons, 10 C100 30-tonne axleload wagons, six K100 30-tonne axleload coal hopper wagons, 10 C70 23-tonne axleload wagons, and 10 C64 21-tonne axleload wagons. Tests were carried out at 60, 70 and 75km/h and led to a number of recommendations for the strengthening
work required to accommodate 30- tonne axleload traffic.
SHR says that the basic track
structure can accommodate 30-tonne axleloads, but this is not sustainable. Track strengthening work will consequently focus on improving track lateral resistance, sleeper bending moment, the anti-overturn capacity of fasteners installed on sharp curves, and to optimise turnout structure and materials by extending frog and point lives.
Testing
SHR subsequently designed and is testing two types of concrete sleepers and fastenings at TTCI’s Heavy Access Load (HAL) test track in Pueblo, Colorado. Trials of the sleepers found positive moment of 22.57kN/m, an 18% improvement on the existing type III sleeper used, a 23% improvement in centre negative moment to 21.33kN/m, while lateral resistance between single sleeper and ballast came to 15.52kN, which is a 7% improvement. Similar improvements were found with the new fasteners, which have a 12mm elastic range and a toe pressure of 12.5kN, a significant gain on current
IRJ August 2013
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