Application of the strain energy ratio and the equivalent thrust per cutter to predict the penetration rate of TBM, case study: Karaj-Tehran water conveyance tunnel of Iran

The penetration rate of tunnel boring machine (TBM) is an important factor in cost and time estimation of excavation operations for project planning and choice of economical tunneling methods. Several methods are used to predict this parameter such as experimental, empirical, and analytical methods. In this study, a new empirical method is proposed to predict the penetration rate of TBM using the actual data of Karaj-Tehran water conveyance tunnel in Iran. It is predicted based on the post-failure residual strain energy to the pre-failure stored strain energy (named strain energy ratio) and the equivalent thrust per cutter. The result shows that there is a direct relation between the penetration rate of TBM and the strain energy ratio, and an inverse relation between the penetration rate of TBM and the equivalent thrust per cutter. In this study, a new polynomial equation is proposed to predict the TBM penetration rate based on the strain energy ratio. Also, a new linear equation is suggested to predict the equivalent thrust per cutter using of the strain energy ratio. Finally, the most useful equation to predict the penetration rate of TBM is achieved using the equivalent thrust per cutter and the strain energy ratio because it is a function of both parameters.