Subproject A6

Local Transient Face Support within Hydro-Shields


The overall objective of the subproject is the development of theoretical and numerical models for the description and mapping of soil mechanical, hydromechanical and rheological changes in the course of the transient penetration process of the tunnel face support with liquid shield in me-chanical tunnel construction. The previous investigations concentrated on the detection of the interaction between bentonite suspension and cohesionless soil during the penetration process. The second possible mechanism of supporting pressure transmission to stabilize the working face is the formation of a filter cake. This cake is formed as surface filtration without and with membrane formation, depth filtration or a hybrid combination of these mechanisms depending on the ratio of the pore size in the loose rock to the size of the dispersed bentonite particles at dif-ferent penetration depths. The cross-scale (macro/meso/micro) investigation of these phenome-na is the focus of the second subproject phase, so that the theories, approaches and results from the first subproject phase are further developed and completed in the course of the work to the penetration process and flow into the modelling of the working face stability under considera-tion of the infiltration processes. This requires several sub-steps, which are divided in six work-ing packages showed in figure 1.

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Fig. 1: organigram of the working packages