For some ten years TBM-techniques have been used to construct tunnels in the Netherlands. Ground conditions vary from loose to dense granular soils, sometimes clays. In all cases groundwater is close to ground level. Front stability is maintained by bentonite slurry or earth pressure balance shields. Several research projects have been initiated by the Dutch Centre for Underground Construction (COB) in order to increase TBM applicability in urban areas. The COB has brought authorities, engineering con-sultants and contractors together in research committees.
One COB research committee is investigating the interaction of soil and the tunnelling process using finite element method (FEM) analyses. The grouting pressure applied to fill up the tail void behind the TBM is believed to govern both deformations and internal lining forces.
Several two- and three-dimensional FEM models that include tail void grouting are available. However, they do not describe time-dependent longitudinal lining deformations or bending moments. As part of this COB project Fugro Ingenieursbureau B.V. has developed a 4D FEM model. The model describes the progressive tunnel boring process using PLAXIS 3D Tunnel software.