Externalities of soil stabilization in the construction of main transportation infrastructures. The case of the High Speed Railway in North Italy: economical and environmental benefit

The technique of soil stabilization is usually adopted with the purpose of rendering plastic soils coherent to the standards and requirements of engineering projects. The environmental benefits of soil stabilization versus the use of traditional natural material from quarries are generally underestimated. The case study of one significant section of the Italian High Speed Railway is presented here. This section is a part of the line from Milan to Venice. The volume of material that is needed for the development of embankments amounts to about 3 million m3 and 1.5 millions m3 of aggregates are needed for concrete. At the same time the construction of foundations produces about 1 million m3 of soil: 350,000 m3 from foundations, 400,000 m3 from diaphragms and drilled piles and 70,000 m3 from helicoidal piles. The need to manage such a significant volume of soil suggests the need for the consideration of recycling the clay soil after lime stabilization. The technical compatibility is here verified. The total costs of all the actions derived from the Environmental Impact Assessment for environment protection is less than 8% of the savings produced by the stabilization of soil. It finally demonstrates that the question of non-renewable resource management, such as soil, is strategic also under an environmental protection perspective.