COMPUTATIONAL MODELING OF FINE SOILS FOR EPB TUNNEL BORING MACHINES

Resumo

In tunnels excavated using EPB (Earth Pressure Balance) machines, the excavated soil must
have some specific engineering properties for the correct functioning of the excavation system.
Therefore, understanding the many characteristics of the excavated material, along with its rheological
behavior, is essential for a successful mechanized excavation. These conditions present obstacles that,
if not foreseen in design, can result in several problems such as soil loss, instabilities, low excavation
performance and damage to TBM components. Aiming at the main goal of creating a procedure of
investigation for fine soils excavated with an EPB tunnel boring machine, this paper presents a
preliminary step, the calibration of a model using Computational Fluid Dynamics approach making
use of a standard soil (bentonite), with a view at investigating tropical soils’ behavior once the
methodology is established. The experimental procedure was carried out using two rheological
methods, Squeeze Flow and an extrusion technique proposed by Benbow and Bridgewater. These
results illustrated that those rheological tests allow to obtain relevant parameters such as yield stress,
viscosity, rheological behavior, useful for planning EPB excavation. The numerical simulation is
important to predict the behavior of different types of mixtures while changing the variables analyzed
in this research. This paper, therefore, shows the experimental and numerical procedures that will be
used to different soils and may be used to other types of materials, to better understand the flow
through the screw conveyor and give parameters to a better soil conditioning system.