Prediction Model for Performance Evaluation of Tunnel Excavation in Blocky Rock Mass

The response of tunnel excavations in blocky rock mass is dominated by the presence of discontinuities. However, many of the studies reported in the literature consider these geological features in a simplistic manner by adopting the equivalent continuum approach, thereby neglecting the structurally controlled mechanism of response. To overcome the aforementioned limitation, the present study adopts the Voronoi tessellation scheme in a discrete-element-based framework to simulate the blocky rock mass. An attempt was made to frame the prediction model for convergence strains of the tunnel by considering the uncertainties of joint parameters and in situ stress ratio. The prediction model was framed following the identification of important parameters affecting the strains using the robust central composite design. Finally, the concept of critical strain was used to demonstrate the applicability of the framed model through the probabilistic assessment of various performance levels of tunnel excavation.