Disc cutter wear/life analysis in a long tunnel excavated in strong to very strong, abrasive rocks

The complex interaction between the cutters and rocks in the tunnel face makes it difficult to predict the cutter wear, exactly. Therefore, many researchers have tried to study this process and introduce different ways to predict the wear extent of cutters and the number of cutters required to complete a mechanized tunneling project. In this study, in addition to investigating the effect of geological parameters on cutters wear/life, new empirical equations were proposed for predicting cutter wear/life, based on data collected from a long tunnel constructed in central parts of Iran, namely Kerman Water Conveyance Tunnel (KrWCT). The data collected from this project, including information related to cutter change stations, variations of geological parameters along the bored section of the tunnel, and actual machine’s operational and performance parameters, were compiled in a database and analyzed statistically. The results of statistical analyses revealed a significant relationship between the cutter wear/life and intact rock properties. Consequently, the proposed empirical prediction equations just employ two important intact rock properties, including rock strength (UCS) and Cerchar abrasivity index (CAI), as inputs. The results showed that the presence of discontinuities with moderate-wide spacing has a negligible effect on cutter consumption. These results also proved that models focusing only on rock abrasivity without considering the rock strength as an input will not provide an accurate assessment of the cutting tool wear. The new models are based on information from a wide range of igneous, pyroclastic, and sedimentary rocks with the UCS and CAI ranges of 50–250 MPa and 0.5-5.0, respectively.