Mechanical performance of TBM cutterhead in mixed rock ground conditions

The mechanical performance of TBM cutterhead including thrust, torque, eccentric force and overturning moment was calculated and analysed in different mixed rock ground conditions. The calculation model was built by identifying the rock type under each cutter using a ray intersection algorithm and calculating the cutting forces of each cutter using the CSM model. The mixed rock ground conditions were simplified as rock type distribution and rock strength classification. In the present paper, the rock distributions of the Layer-Banded Rock (LBR) and Random-Distributed Rock (RDR) types were considered. The influences of rock strength (Uniaxial Compressive Strength: UCS, Brazilian Tensile Strength: BTS), rock locations and number of rock layers were studied. For verification, a boring experiment was designed and conducted using an experimental cutterhead with 14 disc cutters. The rock box was poured with concrete C20, C40 and C60 layer by layer to prepare the LBR condition. The average torque and thrust of the calculation model and experiment were in good agreement. Some conclusions were drawn from the study on the rock strength, rock locations, area percentages of different rock layers and number of rock layers. And hence, some suggestions were proposed to enhance the tunnelling efficiency and reduce damage to the cutterhead.