An Applied Study on the Debris Recycling in Tunnelling

Problem statement: A simple calculation has shown what the impact of muck created during the construction of a hypothetical 50 km long and 100 m² cross section tunnel could be on the environment: around 8 million cubic meters would have to be discharged as waste material. One solution to such a problem could be to recycle (almost a part) the earth material, that is, the muck and debris that are excavated from the tunnel face. Approach: In order to verify the possibility of using some different breakers from the ones used in the handling plant on the studied tunnel-access, some tests were performed in the DITAG laboratory at the Politecnico DI Torino. Results and Conclusion: Different cut dimensions were considered in the recycling of the muck material from the tunnel excavation using TBMs. The obtained material, mixed with natural sands and gravels according to various hypotheses, corresponds to the dimensional requirements for the shotcrete and concrete aggregates. The optimal solution should be the mixture of the best fines produced by TBM, the products of the broken rock and some percentage of natural sands and gravels. The final choice will depend on economic factors and obviously also on the particular features in the work sites.