Soil conditioning with foam during EPB tunnelling / Konditionierung von Lockergesteinen bei Erddruckschilden

In order to extend the range of application of earth pressure balance (EPB) shields in closed mode, conditioning with foam has proved to be particularly effective in coarse-grained soils. The properties of the soil-foam-mixture depend on the support pressure due to the high foam content. The production and dosage of foam up to now has mostly been based on practical experience from job sites. To improve the theoretical basis, research based on realistic foam production has been carried out at the Institute for Tunnelling and Construction Management at the Ruhr University, Bochum, Germany.
Properties of foams and the particular properties of soilfoam mixtures with various injection ratios under atmospheric conditions were specified and analysed. The test results have helped to define operational parameters for foam and also for the first time the range of application of various types of foam generator.