Tunnel boring machine (TBM) has been widely used in mining roadway and various tunnel engineering. However, there is lack of rock breaking prediction models for guidance resulting in the rock breaking theory lagging behind engineering practice. To reveal the rock breakage mechanism of constant cross section (CCS) cutter of TBM, a new analytical model of TBM rock breakage in half space under linear compression of CCS cutter was proposed. The rock breaking mechanical model of the wedge-shaped body of CCS tool was constructed, the shear and tensile rock breaking criteria based on the load transfer mechanism were put forward, and the optimized analytical formula for CCS double-cutter was deduced, and the rock breaking mechanism of CCS tool formed a composite wedge was revealed. Results show that after the composite wedge being formed by the CCS cutter, the composite wedge further compresses the rock mass resulting in tensile failure of underneath rock based on the plane stress analysis. In case of two CCS cutters loading condition, the rock between them is squeezed by 2 isosceles triangles, resulting in subsequent shearing and tensile failures. Furthermore, the wedge prediction model of the rock breaking was proposed underneath the CCS cutter, and it was verified in laboratory linear compression test to obtain validity. The conclusions obtained in this study not only provide a theoretical basis for TBM rock breaking under 3D conditions, but also provide a technical basis for the parameter design of TBM cutting in practice.
 

tunnel boring machine, constant cross section, mechanical model, linear compression, load transfer