Geological and geotechnical considerations on sections of the M25 : Newman, R L Highways TranspV31, N7, July 1984, P18–32

Abstract

The author summarises papers presented by a number of authors at a January 1984 meeting of the Institution of Highways and Transportation held in London. The history of the planning concepts involved in the evolution of the London orbital road is outlined. A resume is given of the geology of the route from the terrace gravels and soft alluvium near Staines, through chalk with glacial cap, boulder clay, reading beds, chalk and clay with flints over. Problems and considerations associated with the earthworks and the selection of plant used at the construction of three large interchanges are discussed. An account was given of the most intensive structural section containing entrained and open cuttings, a cut and cover tunnel and an approach embankment between reinforced earth walls. The Thames Valley stage crossing a number of water filled gravel pits and disused pits is described, and an account is given of the intensive site investigation of the properties of the gault clay in Kent. Some aspects of research design and construction on the route described include the bell common tunnel. (TRRL)