TBM–Block Interaction during TBM Tunneling in Rock Masses: Block Classification and Identification

Abstract

A new block-classification method for tunnel construction using a tunnel-boring machine (TBM) to capture the geometrical and mechanical transformation of rock blocks in the course of TBM excavation is proposed in this paper. The machine–block interaction is interpreted by dividing the joint blocks into blocks influenced by TBM excavation and blocks uninfluenced by TBM excavation. The influenced blocks are categorized further as contacting or noncontacting blocks according to whether they are in contact with the TBM. The contacting blocks include the front block, the corner block, and the rear block, based on the spatial location of blocks with respect to the cutterhead. Different types of blocks have distinct kinematic and mechanical characteristics. The sizes and shapes evolve, and the categories may be changed for rock blocks during excavation. The identification algorithms for influenced blocks and three types of contacting blocks are presented. Finally, a simple example considering a double-shield TBM tunnel excavation is used to illustrate the effectiveness of the new block-classification approach to guide TBM tunneling. The new classification approach will be helpful in evaluating the block removability and the possibility of cutterhead clogging and to shield blockage during tunneling with a TBM.