An empirical approach for predicting ground condition for tunnelling and its practical benefits

While planning a tunnel through a weak rock mass, the first step is to infer whether the tunnel would experience squeezing or non-squeezing ground condition? This decision, not only controls the selection of the excavation method but also the design of support system. An user - friendly empirical approach has been developed to predict the ground condition. Critical values of tunnel depth, rock mass number and tunnel size beyond which squeezing ground condition will occur can be determined using the proposed correlation. This knowledge can be used either to avoid squeezing by realigning the tunnel through shallower depths or through a better rock mass or by replacing the tunnel by two or three smaller tunnels on techno-economic considerations. Should these options not be possible, the advance knowledge can be used to design the excavation and support system for tackling the squeezing ground condition.