Development of an empirical model to estimate disc cutter wear for sedimentary and low to medium grade metamorphic rocks

In hard rock tunneling with TBM, changing worn or damaged disc cutters has a major effect on TBM performance and consequently on constructing time and cost. So, developing reliable methods to estimate disc cutter life in different geological conditions helps to estimate TBM performance and completion time and cost, accurately. In this research, using actual data collected during construction and pre-construction phases of Ghomrood water conveyance tunnel (GWCT) project, an empirical prognosis model is proposed to evaluate cutter wear and life in low to medium grade metamorphic rocks. Data obtained from different stages of this very long tunneling project, including records of TBM performance, operational parameters and cutter wear changes and variations of geological parameters are compiled in a special database and analyzed statistically to obtain reasonable relationships between cutter life or wear and effective geological parameters. Results of statistical analyses showed that correlations between intact rock parameters and cutter wear are reasonable and can be accepted as empirical prediction models for estimating cutter life or wear in similar geological conditions. This proposed model can be applied for limestone and sandstone layers and schistose and foliated rocks including shales, slates, phyllites and green schists with different quartz content and with a UCS range of 30-150 MPa. In this research a comparison was also made between the current model and previous models proposed by the author and his colleagues for different geological conditions. The results show that although these models are similar in shape and inputs, their outputs are different. So, each model must be used according to its application range.