Subproject A4

Model Development for the Conditioned Soil used as Face Support Muck of Earth-Pressure-Balance-Shields


The aim of the subproject in the second funding period was the experimental rheological and hydro-mechanical characterization of foam and particle/soil foam mixtures and the continuum-based modelling based on them as a function of the composition of the fluid mixture. In the microscale, the slump test places high demands on numerical flow simulation. In principle, the explicit (weakly compressible) Smoothed Particle Hydrodynamics (SPH) formulation used allows a simulation of major problems and can also be used for further rheological investigations, e. g. of outflow from a container or silo. To analyze the effects of residual water content laboratory tests were carry out in the macroscale. Based on the results of the foam penetration tests, it is now possible to determine water contents for the conception of soil conditioning for certain situations during tunnelling with EPB shield machines. Furthermore the yield strength and the shear stresses by the shear rate of various soil-foam-mixtures were determined by rheological experiments with the Ball Measuring System.

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Evaluation of the flow curve tests with Ball Measuring System (BMS) for various Foam Injection Rates (FIR 50 - FIR 100) using the flow curve model of Herschel-Bulkley

Residual water content of different test soils after the foam penetration test. The black line indicates the water content for a typical Earth Pressure Balance (EPB) tunnelling situation (1.0 rpm, ntool=8, htool=20 mm)

Results of single-phase Smoothed Particle Hydrodynamics (SPH) simulations of a fluid with non-Newtonian rheology. Left: normalized velocity profiles for creepage currents (shear flow) with a power law rheology. Right: The chronological development of the "slump" during a "slump test" The numerical solution is based on a regularized floating voltage model (Bingham-Papanastasiou