Influence of muck properties and chamber design on pressure distribution in EPB pressure chambers – Insights from computational flow simulations.

• Numerical models for muck transport in different EPB chamber designs established. • The chamber design has a strong influence on pressure fluctuations. • Larger levels of yield stress and viscosity lead to a larger pressure unbalance. • Smaller muck compressibility and high pressure levels lead to higher fluctuations. • Pressure drop at the screw conveyer entrance may propagate to the tunnel face. Earth Pressure Balance (EPB) shield machines are widely used in mechanized tunneling operations in soft grounds. In contrast to slurry shield machines, the pressure distribution in EPB excavation chambers is not well undersood, as it is influenced by the muck properties and the chamber design. A computational model specifically developed in Dang and Meschke (2018) for the numerical simulation of material transport in EPB pressure chambers is employed to investigate the pressure distribution in two different types of EPB chambers, characterized by a different design of the mixing components, the rotators and the screw conveyor. The numerical model allows for the description of all rotating and fixed components of the EPB chambers including the screw conveyor and considers adequately the compressibility and the consistency of the soil paste. The spatio-temporal pressure distribution is investigated with respect to the influence of chamber design and the properties of the soil paste. Essential characteristics of the pressure distribution, such as the pressure unbalance between the left and right side and pressure fluctuations observed in in situ measurements are captured by the numerical analyses. The key factors influencing the pressure unbalance and pressure fluctuations are identified by parametric studies for two different EPB chamber designs. [ABSTRACT FROM AUTHOR]