Rheological characterisation of earth-pressure-balance (EPB) support medium composed of non-cohesive soils and foam

The flow behaviour of soil-foam mixtures, used as support medium in closed mode tunnelling with EPB shields, is an essential factor for the operation of the TBM. This thesis focuses on the rheology of soil-foam mixtures aiming at an extended understanding of the flow behaviour and of the influences the individual components have on it. An experimental programme was elaborated, which dealt with two main scopes: a discussion on the slump test and its value as index test for the flow behaviour of soil-foam mixtures and secondly, the application of rheometer tests to soil-foam mixtures. Rheological tests on various scales were performed with a variety of soil-water-foam mixtures in order to determine flow curves and thus to characterise their flow pattern. From this multi-scale analysis, it can clearly be shown that the flow behaviour of soil-foam mixtures is very dependent on the particular shearing condition.