Abstract
AbstractThis paper investigates the interaction between tunnel boring machine (TBM) and ground under severe squeezing conditions, characterized by very large deformations of the ground at and ahead of the tunnel face. The effect of core extrusion is studied considering undrained conditions. In order to quantify the ground extrusion at the tunnel face during the TBM advance, a novel step-by-step numerical procedure was developed, based on the finite element method (FEM), considering material and geometric nonlinearities, and employing re-meshing and stress re-mapping techniques. The numerical analyses show that the volume of the excavated ground may considerably exceed the tunnel volume and this although the tunnel face is stable. This is because the TBM excavates also the ground that enters into the tunnel cross-section ahead of the tunnel face and extrudes during advance at the face. Under extreme conditions the additional excavation volume may reach 50–100% of the tunnel volume.KeywordsSqueezing groundTBM advanceUndrained conditionsTBM-ground interactionFace extrusion
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