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  Influence of Soil Conditioning on the Flow Behaviour of EPB Face Support Medium

  The flow behaviour of the face supporting medium in Earth-Pressure-Balance (EPB) tunnelling is a decisive criterion for an efficient tunnel advance. The support medium needs to exhibit rather fluid properties in the excavation chamber in order to establish a quasi-hydrostatic support pressure distribution, while in the screw conveyor and on the conveyor belt a rather stiff consistency is required for pressure control and disposal. Since EPB shield machines nowadays need to cover the full range of ground conditions in both soils and rock conditions, the application of chemical additives has to be considered to make TBM tunnelling feasible. Soil conditioning has become a common method extending the typical application range of EPB shields from clayey and silty soils towards non-cohesive sands and gravels.In this contribution, the authors are going to present recent results on the influence of soil conditioning on the flow behaviour of non-cohesive grounds. Common approaches from literature and tunnelling practice are being compared to latest rheological perspectives. Based upon laboratory findings, requirements for an effective soil conditioning and for a suitable flow behaviour will be presented providing benchmarks for designing the soil conditioning process successfully.

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