ABSTRACT
Damage to concrete segments is inherent to shield driving of segmented concrete tunnel linings. Almost in all cases they occur during the assembling stage. It is ever more becoming clear that the assembling stage is the most critical phase in the construction process. However, due to inability to take into account all aspects that play a role in the complex situation that exists during tunnel driving and segment erection, many-tunnel designers only consider the serviceability stage (‘final situation’) and try to minimise the effects of (unknown) assembling stresses by optimising lining design and execution procedures. Although minimising assembling stresses is an essential thing to do, thinking unintended stresses can be eliminated this way is an illusion. It would be very useful if one could predict these stresses, so the tunnel lining could be designed to resist them.
In order to overcome these kind of problems Project Organisation High Speed Line South developed a three dimensional FEM model in which typical assembling are involved. The model is capable of doing a staged simulation of the building process: new tunnel rings are oriented and placed on already built and deformed rings, while loading at the total system is changing due to building progress (hardening grout, steering the TBM). This volumetric model has been modelled very accurate: tapered rings, exact joints, joint materials, joint sealing, cracking of concrete, equivalent system support (representing non modelled lining, beyond major influence zone), etc. By using newly developed, powerful post-processing programs bending moments in all directions, hoop forces and rotation of joints can be extracted quickly. Design is still based on forces en deformations, but now also for the construction stage, which was not available in common design practice. The model is parametric and post-processing delivers main results in engineering ‘language’ in no time.
This paper shows a brand-new model, created very close to real geometry’s and describes results of damage mitigation during construction. The model provided already very useful arguments on damage control and reliability for the ‘Green Heart Tunnel’, the next shield driven tunnel with the largest diameter of about 15m.
