A numerical model for the tunnel boring machine interaction with soil
Mechanized shield tunnelling is a reliable way of constructing tunnels in soft soil, particularly in urban areas. However, a lack of understanding of the physical interaction between the TBM-shield, the soil, and the process fluids contributes to the long learning curves often experienced and hinders improvement of the machine’s driving rationality. A numerical shield-soil interaction model is proposed that bases the extent and spatial distribution of the displacements induced by the advancing shield on TBM monitoring data. The model includes the unloading-reloading condition of the surrounding soil and the possible infiltration of process fluids around the shield periphery. This infiltration influences the equilibrium of the TBM. A set of novel soil reaction curves is also introduced specifically to model a TBM interaction with the surrounding soil. The study offers an innovative outlook on the tunnelling related soil displacements. Results indicate that a more rational approach to mechanized shield tunnelling in soft soil is possible.
Kinematic behaviour of a Tunnel Boring Machine in soft soil: Theory and observations
Abstract State-of-the-art shield tunnelling in difficult ground conditions still involves a trial-and-error approach as a complete understanding of the physics governing the interaction between the Tunnel Boring Machine (TBM)-shield and the surrounding soil is still lacking. This is particularly concerning as it was demonstrated that the shield–soil interaction, and especially the ground displacement around the shield periphery, gives a significant contribution to the overall soil deformation. This paper quantifies the radial soil displacements induced by a TBM-shield driving in soft ground. The displacements have been obtained by means of a model that captures several aspects of the kinematic behaviour of a TBM, based on theoretical and geometrical considerations. The theoretical model has been verified against TBM monitoring data obtained during the construction of the Hubertus Tunnel, a double-tube road tunnel located in The Hague, The Netherlands. Results show the amplitude and spatial distribution of the ground displacement around the shield periphery as they occurred in practice.
Numerical modelling of partially saturated soil and simulation of shield supported tunnel advance
For the holistic and process-oriented simulation of mechanised tunnelling two aspects have to be considered: on the one hand side a numerical description of the construction process is required and on the other hand side a sufficiently accurate modeling of the surrounding underground has to be applied. To achieve such a simulation model first, a Finite Element Model for the description of partially saturated soil as a three phase material is developed. Second, the interactions between the tunnel construction process and the surrounding undergound - via the heading face support, by frictional contact between shield skin and soil and due to grouting of the annular gap - are discussed and adequate sub-models for their numerical consideration are developed. Selected simulations of real scale examples including the analysis of a compressed air intervention demonstrate applicability of the so-developed simulation model for shield supported tunnel construction.