In Switzerland, over the next 10 to 15 years approximately 80 million cubic metres of excavation material will be extracted from the tunnels which remain to complete the construction of the national roadway network, the Rail 2000 project and the new Alp Transit railway lines. According to the environment law and following the principle of sustainable development, only a small portion of this material can be landfilled and its use is virtually obligatory.
Excluding the limited possibility for reuse at the tunnel where it was excavated, this material should be used for other construction projects. Roadway construction could probably account for most of the extracted material not used on the spot. The case of tunnels in rock excavated using a tunnel boring machine, which is becoming more and more frequent, poses specific problems for reutilization because of the unfavourable shape of the rock pieces and the poorly graded grain size of the excavated material.
The aim of this research is to determine a methodology for the research for solutions in view of the use of these materials for civil engineering purposes and, in particular, for roadway construction (surface and foundation layers, fill and other uses); to define necessary methods for the qualification of these materials as a function of their origin and use, any further treatment and their placement method.
Key results of the project are:
- a methodology for use of materials
- definition of methods for materials qualification
The final report contents firstly a summary of the geological characteristics and geomechanical major Swiss geological formations.
Next chapter brings the characteristics of the excavated material according to the mode of travel. The treatment needed in the manufacture of materials used in the road sector are then discussed and the requirements defined in the Swiss standards for different possible uses.
Finally, it outlines the experiences of valuation tunnels excavated material made in our country. Fourteen works particularly representative of different geological formations traversed and experienced various methods of treatment were selected to be an investigation to identify the methodologies devised for material selection.