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Chapter 4: Earthworks and drainage

As we have seen in Chapter 3 earthworks are required to provide a stable, durable platform for constructing the pavement: the slopes of embankments and cuttings must be similarly stable and durable. In the early years of the motorway programme the construction of earthworks was largely a matter of shaping the landscape, screening out unsuitable materials and compacting what remained to provide a stable platform for construction that would remain so for the lifetime of the pavement. The first part of this chapter deals with advances made in these early years, marked by a steep learning curve and reflected in the production of improved specifications. The second part deals with later developments including the use of geomaterials and other techniques for improving the quality of soils and other earthworks materials; it covers the development of sophisticated earth structures and leads on to the increasing use of ‘design and construct’ contracts and the growth of innovative technologies. Finally in the third part of the chapter we deal with the drainage of water from the pavement surface and the subgrade beneath the pavement.

The chapter has been compiled by Maurice Maggs. David Farrar, formerly of TRRL, has contributed from his experience of research on bulk earthworks, while the section on reinforced earth owes much to contributions to the Archive by Chris Jenner of Netlon and Rod Smith of Elwood Consultants: the section on drainage is largely the work of Ron Bridle.

The following subjects are covered in the printed document (Volume 2):


Research at RRL
Soil Surveys
Earthworks Construction
Specification Development


The Vidal patents
Subsequent Development
BS8006: Code of Practice for Stengthened/Reinforced soil
Contract Arrangements


Ground Water
Surface Water