TBM Excavability Classification of Surrounding Rock Based on FPI

Due to the huge investment of tunnel boring machine (TBM) in the early stage, it is of great significance to reasonably classify the excavability of TBM surrounding rock and give the suggested values of construction parameters for predicting the construction period and controlling the cost. The TBM construction project of Yangtaishan hard granite tunnel in the section 6101 of Shenzhen Metro Line 6 between Dalang station and Shiyan Station is taken as the research background. Firstly, the tunneling penetration index (FPI) is taken as the tunneling performance evaluation index, and Spearman correlation was used to analyze the rationality of FPI as an evaluation index. On this basis, FPI is used as the input parameter to establish the penetration degree prediction model, cutter head thrust prediction model and driving speed prediction model, and the reliability of the models is verified based on the right line driving data of Yangtaishan tunnel. Based on the K-means clustering method and FPI clustering index, the excavation grade of surrounding rock was divided. According to the prediction formula of tunneling parameters given in this paper, the recommended values of tunneling parameters corresponding to the excavation grade were given. The results show that: (1) FPI can reasonably reflect rock-mechanism system in TBM construction to a certain extent, and can be used as an evaluation index of tunneling performance. (2) The prediction formula of TBM tunneling parameters established in this paper has a good correlation coefficient R² of 0.75, 0.98 and 0.97, which can accurately provide prediction parameters for TBM tunneling. (3) The classification model of TBM surrounding rock excavability established in this paper divides surrounding rock into five grades, and the tunneling parameter values under different levels are determined.