Sunday 23 August 2009

For Anoraks!

Digging the trench for the water pipe unearthed the layers of "Blanketing" used by the Great Western Railway to suppress the impact on ballast, sleepers and rails of the heavy clay sub-strata in this region.

Jim the Knowledge's explanation: "Most of the railway infrastructure that goes through Broadway to Cheltenham cuts through clay in cuttings the clay forces its self through the ballast the problem of course is exacerbated by the passage of trains. In 1949 British Railways decided to invest in new rail and took the opportunity to deal with the clay issue. This required single line working rail out all ballast removed a trench was also dug in the cess and fill with up to six courses of 9 inch blocks to act as a barrier between the clay and new ballast at the same time a thick layer of fine sharp sand mix was unfilled followed by new ballast the sharp sand mix and block barrier combination reduced the problem if clay ingress.

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