This paper describes the construction of a full scale trackbed load test facility which simulates the harshest conditions under which a geosynthetic layer is likely to be used. A background to the use of geosynthetics as separators between ballast and formation in the UK is given, together with a discussion of the scope for further development. The initial test schedule is described, which confirms that the loading conditions are representative of those experienced in typical main line traffic, followed by a summary of early tests on geotextiles in common use to assess their resistance to abrasion damage.
The use of geosynthetic products in the UK as separators between ballast and formation has developed gradually since the introduction of the first geotextiles in the 1970’s. After many years of experience the use of geosynthetics on the UK rail network has been standardised. This approach is necessarily conservative, since the cost of formation failure is high. While the incidence of failure is minimised, standardisation does not exploit the full potential of geosynthetics; neither does it encourage innovation. In the past various innovative products have been proposed, but difficulties have been experienced in taking them forward to the stage where there was sufficient confidence to undertake site trials. One of the main obstacles was the lack of suitable test facilities that would replicate the harsh environment encountered beneath a main line railway, which made it difficult to evaluate new products.
In 2001 a full scale trackbed test facility was constructed at Liversedge in order to undertake accelerated testing of geosynthetics under realistic loading conditions. The facility was supported by the DTI and a consortium that included leading rail maintenance contractors, industry suppliers and academics.
After the initial test programme was completed, confirming that conditions in the rig simulated those encountered under main line conditions, formation conditions in the rig have been adapted to simulate the harshest conditions under which a geotextile would ever be expected to survive. Tests have been completed on three commonly used geotextile separators to assess their resistance to abrasion damage.
In 2010 Geofabrics launched a new anti pumping geocomposite in the UK, which could be used to prevent the development of mud pumping.
This paper describes the development process undertaken to produce a lightweight, geosynthetic filter to replace a sand-blanket used within trackbed.
RK4 - a textile/grid composite, was installed to stabilise the ballast/subgrade interface and reduce the upward movement of subgrade fines.
TrackTex™ Anti-Pumping Geocomposite was used to to provide an increased form of ballast protection in known trouble areas in Christiansburg, Virginia.
TrackTex anti-pumping geocomposite was selected by Network Rail as a method of preventing mud pumping and prolonging trackbed performance.
A statement by Gordon Donald, Managing Director of Geofabrics, regarding the judgement on patent infringement by Fiberweb Geosynthetics Ltd.
TrackTex was installed on a frequently trafficked diamond crossing as a long-term effective remedy to frequent fouling caused by mud-pumping.
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