Abstract
In the construction industry, especially in tunneling or large-scale earthworks projects, huge quantities of excavation material are generated as a by-product. Although at first glance such material is undesirable, in many cases this material, if suitably treated and processed, can be recycled and reused on the construction site and does not necessarily need to be removed and deposited as waste at a landfill. In the simplest case, the material can be used as filling material with the least demanding requirements with regard to rock quality. Material of better quality often can be recycled as aggregate and be used as a substitute for conventional mineral aggregates. This approach generates numerous benefits regarding the costs for material procurement, storage and transport. In addition, reduction in environmental impact and demand for landfill volume can be achieved. The challenge lies in the fact that excavation material is not a standard aggregate in terms of geometric, physical and chemical characteristics and is subject to quality deviations during tunnel driving, mainly depending on the varying geology and applied excavation method. Therefore, preliminary research and experimental testing as well as specific evaluation and continuous examination of the rock quality during tunnel driving is necessary as well as ongoing adjustment of the rock processing plant to finally accomplish a high-quality level of recycled aggregates. This article illustrates the material investigations and treatment processes for the specific example of the Brenner Base Tunnel, the longest underground railway line in the world that is currently under construction. There, material recycling has already been successfully implemented.
Highlights
In Europe, the mountain chains of the Alps stretch from the Gulf of Genoa to the lowland plains of Hungary, separating the main economic regions within the European Union
Large quantities of excavation material from the bedrock are generated as an unwanted by-product or “waste”, whereby handling and treatment of tunnel excavation material is a fundamental subject in a tunnel construction project, often deciding on the economic and environmental success of the construction project itself [1,2]
The aim of this article is to demonstrate the recycling process of tunnel excavation material as substitute for conventional aggregate by the example of the Brenner Base Tunnel in Austria, illustrating the scientific approach, experimental setup as well as the practical implementation accompanied by experimental verification due to its challenging geological bedrock conditions
Summary
In Europe, the mountain chains of the Alps stretch from the Gulf of Genoa to the lowland plains of Hungary, separating the main economic regions within the European Union This is why tunnels and especially railway tunnels of significant length are essential to ensure the functional capability of the overall network. Numerous tunnels have been built in the past and are currently under construction or in the planning process. The aim of this article is to demonstrate the recycling process of tunnel excavation material as substitute for conventional aggregate by the example of the Brenner Base Tunnel in Austria, illustrating the scientific approach, experimental setup as well as the practical implementation accompanied by experimental verification due to its challenging geological bedrock conditions. There, the reuse of rock material mostly excavated during continuous tunnel driving at a variable geology is a demanding task with a particular importance regarding quality management due to its use for high-grade concrete products such as lining or structural concrete
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