EPB-TBM cutterhead torque and thrust modelling in rock tunnels through an analytical method and TSFS model

The analysis of cutterhead torque and thrust force is of utmost importance in the selection of a proper tunnel boring machine (TBM) and in achieving optimal operation of the earth pressure balance (EPB) machine for a specific project. This study focuses on the analysis of cutterhead torque and thrust force using data collected from the recent metro project of Tehran, specifically the southern extension of Tehran metro line 6, (TML6-SE). To assess the impact of geotechnical and operational parameters on the measured torque and thrust, a database consisting of 457 data points was established. The excavation of a significant portion of the project took place in a dense and robust limestone using a refurbished EPB machine with a diameter of 9.19 m, initially designed for soft ground excavation. To complete this section of the tunnel, the cutterhead was equipped with disc cutters instead of rippers. Consequently, existing theoretical models for estimating torque and thrust of an EPB machine were modified to accommodate the hard rock boring process. Additionally, the Takagi-Sugeno fuzzy system (TSFS) was utilized in this study. The results of the models yielded quantitative conclusions, and the comparison between the measured and predicted target parameters demonstrated high accuracy. This study contributes to the understanding of the influence of various parameters on the performance of EPB machines in hard rock boring conditions, as well as providing insight into the potential adjustments needed in theoretical models for predicting cutterhead torque and thrust force. The proposed models showed satisfactory and reliable accuracy, with all models having an R2 value above 0.7 and loss function values nearing zero.