Cutter wear evaluation from operational parameters in EPB tunneling of Chengdu Metro

Cutterhead inspection and maintenance is an important reason for operational delays in EPB tunneling project. In order to minimize the number of maintenance stops, non-entry evaluation of cutter wear is required. This study introduces a new prediction model for cutter wear based on automatically recorded operational parameters including cutterhead torque, rotational speed and flow rate of foaming liquid. Real-time operational data was processed to obtain two robust input variables including work done by cutterhead torque and volume of foaming liquid. Field data from 20 tunnel sections of Chengdu Metro were then analyzed to develop quantitative relationships between the two input variables and cutter wear. These tunnel sections were excavated by two types of EPB machines in gravels and weathered rocks. The analyzed real-time operational data covers an excavated length of 14140 m. To ignore the influence of tunnel diameter, prediction model of cutter wear per unit volume of excavation was also developed. The proposed models provide reasonable evaluation of tool wear (R-2 up to 0.857) in gravels and weathered rocks, for which cutter wear prediction based on geological parameters is rather difficult because of huge variation of the materials.