An application of rock engineering systems for estimating TBM downtimes

TBM performance prediction is essential for estimation of project duration and costs in mechanized tunneling projects. An accurate machine prediction is dependent on rock mass and geological exploration conditions including rock strength, discontinuity conditions, hardness, underground water, poisonous gases, instability and mixed face conditions. The relative contribution of these conditions would have a significant effect in TBM downtimes and reduce the machine utilization considerably. Nonetheless, there are few documents in the literature regarding the prediction of TBM utilization factor. Utilization factor is one of the key performance parameters that links the advance rate and penetration rate, mostly affected by the type of operation, management, maintenance, and geological conditions. Rock engineering system (RES) is a valuable analytical tool for characterizing the important parameters for the interaction mechanisms among variables in rock engineering problems and other engineering practices. The main objective of this study is application of RES for calculating geology and rock mass related downtimes index (GRDi) based on predominant rock mass properties and rock mass related downtimes. This approach was applied to a database of three long mechanized tunnels. Developed database contains geological maps, detailed engineering geology information and daily site reports including length of excavated tunnel in each rock mass units, daily boring time and different rock mass related downtimes. Results of this study showed that GRDi is a robust approach for generating a better fit and producing more reliable and accurate estimation of TBM downtimes compared to conventional statistical methods (R2 = 0.849).