Analysis on the Evolution of Rock Block Behavior During TBM Tunneling Considering the TBM–Block Interaction

It is important to consider machine–block interaction when assessing the stability of tunnels excavated by tunnel boring machine (TBM) in blocky rock mass as the behavior of rock blocks changes with TBM progression. The cutterhead motion (advancement and rotation) alters the geometry of rock blocks and the cutters acting on the block. As a consequence, the contact forces between the cutterhead and rock blocks change, which leads to the variation of block kinematics and stability. This paper extends the traditional block theory to analyze the life-cycle behavioristics (morphology, mechanics, kinematics and stability) of rock blocks during TBM tunneling considering TBM–block interaction. The morphology analysis follows the traditional block theory but considers TBM–block interaction. The cutterhead–block interaction is decomposed into a normal component and a tangential component, both of which depend on cutterhead motion. The removability conditions and mechanical equations for three traditional translational modes and two rotational modes are derived, based on which the kinematics and stability of rock blocks during TBM tunneling can be determined. Implementation of the proposed methodologies in reflecting the dynamic evolution of block behavioristics in the process of TBM tunneling is demonstrated through a generic example.