On the Interaction between a Tunnel Boring Machine and the Surrounding Soil

Abstract

The thesis investigates the mechanical equilibrium of a Tunnel Boring Machine (TBM) driving in soft soil. The interaction between the TBM-shield and the soil is also investigated. The analysis is based on monitoring data gathered during the construction of the Hubertus tunnel in The Hague, Netherlands. The monitoring activities during tunnel construction are discussed in detail. Special care is given to explain how the recorded data can be processed in order to verify a number of physical processes induced by the TBM-shield advance. TBM-data (machine data) and soil monitoring data (from inclinometers and extensometers) are examined. A kinematic model of TBM-shield behaviour is constructed from theoretical and geometrical considerations. The consequences of driving a TBM-shield in a curve are highlighted and validated against the TBM monitoring data. It is demonstrated how the kinematic model can provide the displacement history of the soil induced by the TBM-shield. Stresses, forces and moments acting on the TBM are covered in detail. Active and passive forces are combined and the equilibrium of the TBM-shield is considered by means of a purpose built numerical model. It is discussed which model features produce favourable conditions to the achievement of static equilibrium and which others may still hinder it. A quantitative assessment of the influence of the tail-void grouting is undertaken and uncertainties regarding the soil stiffness are discussed. It is observed that a considerable amount of the total tunnelling induced soil displacements occurs during the phase of temporary support. It is also demonstrated that the pattern of the induced displacements is more articulated than assumed in the volume-loss scheme.