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Currently, a tunnel boring machine (TBM) is widely used in tunneling. TBM is a full-face machine, therefore the face cannot be observed. This is disadvantageous especially in rapidly changing conditions, as is commonly the case for rock mass in Japan. In previous paper, equations (1) and (2) for estimating rock strength of face with TBM cutting force are proposed based on experimental findings.σc = FN / c1p ……(1)σc = TR / c2p1.5 ……(2)σc: rock strength p : cutting depth FN : thrust force TR : torque.Constants c1 and c2 in equations (1) and (2) should be the function of the specifications of TBM(tunnel diameter, cutter diameter, cutter distance etc.). In this study, the relationship between constants (c1 and c2) and specifications of TBM was examined for ten tunnels.It was found that constants c1 was strongly influenced by a cutter diameter d.c1 = n(4.37d-1.43) ……(3)n is number of cutter. With increase of a cutter diameter, not only contact area with rock, but also apparent strength of rock increased.Constants c2 was also influenced by tunnel diameter and cutter diameter.c2 = n(2.19-0.1D)(4.37d-1.43)……(4)By equation (1) ∼ (4), thrust force and torque of TBM can be estimated if necessary information is available.

Relationship between Specifications and Cutting Forces of TBM.