Study on the influence of confining stress on TBM performance in granite rock by linear cutting test

• The full-scale cutting tests with different confining stress were firstly conducted to study the effect of confining stress on TBM performance in this paper.
• Based on the results of the effect of confining stress on the cutter normal force, rolling force, the cutting coefficient and specific energy, the optimum parameters for TBM operation under stressed conditions were suggested.

Rock stress problems induced by overburden or anisotropic stresses are significant to the TBM tunneling. In this paper, the effect of different confining stressed conditions on TBM performance are investigated by using full-scale cutting tests with large intact granite specimens (1000 mm × 1000 mm × 600 mm). In these tests, the effects of confining stresses on the normal force, rolling force, the cutting coefficient and specific energy are analyzed. It is found that the confining stress has significant impact on the normal force and rolling force. Specifically, for the same cutting spacing and penetration depth, the normal force increases with increasing confining stress due to enhancement of the rock resistance strength; meanwhile the rolling force decreases gradually with increasing confining stress. The stress deviation between two confining directions affects the optimum penetration that corresponds to small specific energy. The results provide better understanding of the effect of confining stress on the TBM performance and also recommend some guidelines for TBM tunneling under stressed geological condition.