Preliminary identification of potential failure modes of a disc cutter in soil-rock compound strata: Interaction analysis and case verification

The reliability of a disc cutter is critical to shield tunneling performance in compound strata. In this regard, a series of three-dimensional models were developed to evaluate the interaction between the disc cutter and the soil-rock interface. The influences of the penetration depth and the tip width were also addressed. Then, this study presented a rudimentary identification method of disc cutter's potential failure modes in compound strata. The results convincingly indicated that the cutting coefficient could be separated into two stages at the interface of soil and rock: linear reduction stage and constant value stage. For a disc cutter with a tip width of 20 mm and 22 mm, about 1.5% and 1% increments were added to Cc,r as the disc cutter penetrated every millimeter deeper, respectively. It showed that a cutter ring was apt to fracture at the soil-rock interface. The risk of cutter ring fracture was mounting dramatically as the penetration depth raised. The fracture failure possibility at the soil-rock interface for a narrow cutter ring was higher under a great thrust. And it also revealed that the cutter ring of a disc cutter might be led to non-uniform wear due to the insufficient starting torque to rotate in soft layers. Overall, the conducted research could offer helpful guidance for TBM operation in the compound stratum.