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Short note: Telford construction

Short answer

Telford construction places large hand-set stones on edge as a foundation, covered by layers of broken stone, totaling about 400-450 mm. It provides a very strong road on weak soil but is slow and expensive, replaced by Macadam's method.

Write a short note on Telford construction.

Telford construction was developed by the Scottish engineer Thomas Telford (1757-1834) in the early 1800s. It builds the road on a strong foundation of large stones to carry the load and keep out moisture from the subgrade.

Features

  • Foundation layer: large stones (about 170-250 mm), set by hand on edge with the broader face down and narrower end up; gaps are filled with small stones and well rammed.
  • Middle layer: about 100 mm of broken stone (about 65 mm size) over the foundation.
  • Top layer: about 40 mm of smaller stone (about 25 mm) with binding material.
  • The subgrade is nearly flat or slightly cambered; the cross slope is made by the varying thickness of the stones; the crown is about 1 in 45 to 1 in 60, with side drains.
  • Total thickness about 400-450 mm.
   ___ 40 mm top layer ___
   === 100 mm broken stone ===
   ##### hand-set stones #####
   ------ flat subgrade ------

Merits and demerits

  • Strong, durable and good for weak soil.
  • But costly and slow because of skilled hand-setting, so Macadam's cheaper method replaced it.

✓ Answer checked by Claude Opus 5.5 (high effort)

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