Earthworks Manual

The general considerations in Part 1 show in summary the earthworks process and the different phases of construction of earth-structures.

The Part 2 develops the specific, transverse technical topics that are most relevant to our field.

These topics are dealt with in depth in order to promote the sharing of knowledge of specific earthworks techniques and methods. They are based in particular on feedbacks and technical references resulting from previous PIARC work and also from more recent work, espacially European work.

The developments focus on the following strategic vectors:

  • The utilisation of resources made of materials in their natural state due to their appropriate intrinsic properties, or which can be improved by treatment techniques for optimal use.
  • Economical and environmental aspects are considered and are to be optimized at the various stages of design and execution of the project.

Part 2 consists of 5 booklets:

2A - Materials

The optimal utilisation of materials, locally available on the site, of a road project is today a priority, both from an economic objective and an environmental objective contributing to sustainable development.

Consequently, the identification and knowledge of the resources that materials constitute, are fundamental and require in-depth and high-performance studies.

The materials used in the construction of earth-structures of a road infrastructure come from various sources. We mainly distinguish:

  • natural materials, soils or rocks, available locally on the road project site: cuttings or borrowings; or where applicable, when necessary, borrow pits or quarries (materials most often transformed by mechanical processing operations: screening, crushing, ...).
  • marginal natural materials, when a methodology for using these materials may be appropriate for optimal use.
  • possibly, alternative materials when available close to the project: industrial by-products, non-hazardous waste, etc… the use of which may be of significant environmental interest.

The different types of materials that constitute resources for an economic infrastructure project are presented in 3 booklets that can be downloaded from this page:

  • 2A.I Natural materials soils and rocks,
  • 2A.II Case of marginal materials,
  • 2A.III Alternative materials.

2B - Treatment of materials

The Booklet 2B downloadable on this page deals with the treatment of materials.
This technique is increasingly carried out to optimize the use of materials under economically advantageous conditions.
For Earthworks, the process involves the treatment of natural soils and weak rocks, as well as recycled or artificial materials.

The most developed techniques are:

  • short-term soil improvement, applied in particular for excavated materials.
  • medium- and long-term stabilisation, generally applied to capping layers and pavement subbases

The treatment products considered are mainly lime and/or hydraulic binders.

The choice of the treatment solution is based on economic and geotechnical studies. The process is defined according to a multi-stage formulation study. An assessment of the suitability of the material for treatment is essential.

The soil treatment technique is described for the construction of embankments and capping layers. The use of the appropriate equipment, among the range described in this Booklet, is essential for the execution of the project.

The various recommended controls are also discussed.

2C - Earthworks project
2D - Earthworks execution and controls
2E - Environmental aspects


PART 1 - General considerations
PART 2 - Specific technical development

Information sheet

  • Date : 2021
  • Author(s) : Comité technique / Technical Committee / Comité Técnico D.4 Terrassements et routes non revêtues / Earthworks and Unpaved Roads / Obras de tierra y caminos no pavimentados
  • Domain(s) : Road Earthworks
  • PIARC Ref. : 2021R02EN

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