Investigation on disc cutter behaviors in cutting rocks of different strengths and reverse estimation of rock strengths from experimental cutting forces

This paper investigates the disc cutter behaviors in full-scale linear cutting tests. The experimental results obtained from different rocks varying from relatively soft rock (sigma(c)=27.6 MPa) to extremely hard rock (sigma(c)=355.54 MPa) are compared to the results of the semi-theoretical prediction model (Rostami & Ozdemir, 1993; Rostami, Ozdemir, & Nilsen, 1996). Compared to the semi-theoretical results, higher experimental normal and rolling forces and lower experimental cutting coefficients and normalized resultant forces are obtained when cutting low strength rocks. Opposite results are found when cutting extremely hard rocks. An empirical disc cutter cutting force prediction model is suggested in which the input parameters are cutter diameter, cutter spacing, cutter penetration depth and rock uniaxial compressive strength. Furthermore, based on the semi-theoretical model and the new empirical model, reverse estimation of rock strengths from disc cutter cutting forces are undertaken. The results show that rock uniaxial compressive strength can be reliably evaluated from disc cutter cutting forces, but the estimation results for rock Brazilian tensile strength are not so good. This study is pertinent to the better understanding of the disc cutter behaviors in cutting rocks of different strengths and can improve the geological information acquisition and operation control during TBM tunneling.