Shields Machines in Fine Grained Soils: Results from Laboratory Research to Reduce the Clogging Potential
Tunnel drives with EPB- and slurry shields in fine grained soils could lead to clogging e.g. at the cutting tools and in the excavation chamber. During tunnel drives using EPB-shields the clogging potential will be in common reduced by changing the consistency index of the support media in the excavation chamber or using additives. During tunnel drives with slurry shields in common additives are used to reduce the risk of further clogging. In advance of a project systematically investigations to reduce the clogging potential of fine grained soils for shield machines are unusual. So, numerous tests with different soils from international projects were carried out in the laboratory of ELE Beratende Ingenieure GmbH (ELE) to investigate the adhesion tension in order to describe the clogging potential for EPBand slurry shields systematically. In these laboratory tests water and different additives were used to change the properties of the soils and to simulate the soil conditioning of EPB- and slurry shields. Based on these new results it can be shown that a reduction of the adhesion tension is possible and the correct use of additives could have a significant influence on the project’s tunnel drive and the economic efficiency of a project.