Abstract:

Uniaxial compressive strength σ_cm of rock mass is a crucial mechanical parameters affecting the excavation and support optimization of tunnel boring machine (TBM) surrounding rock. To rapidly and accurately evaluate in-situ rock mass mechanical parameters in TBM engineering, a comprehensive TBM database with 159 sets of rock mass characteristics, tunneling parameters, and technical indexes was developed from four typical long-distance hard rock tunnels in China. Additionally, the specific energy SE_TBM theoretical equation, suitable for the TBM cutterhead rock breaking system, was proposed and derived. The empirical model between SE_TBM and σ_cm was established, and its validity was verified and discussed. The results show that, compared to FPI, SE_TBM effectively eliminates the influence of varying TBM excavation parameters and technical indexes, serving as a new reliable index for accurately evaluating rock mass excavatability. The empirical relationship of uniaxial compressive strength of rock mass derived from four rock mass classification criteria demonstrates strong performance (coefficient of determination R²>0.84), with the prediction model based on rock mass integrity index K_v exhibiting the best performance. The new model’s average relative error for predicting uniaxial compressive strength of rock mass, modified by upper and lower limit equations, is 11.37%, indicating high overall prediction accuracy. Utilizing extensive TBM tunneling parameters offers a novel approach to quickly estimate the uniaxial compressive strength of in-situ rock mass.

Key words: tunnel boring machine, uniaxial compressive strength of rock mass, tunneling parameters, classification system of rock mass, specific energy