Evaluation of geological conditions ahead of a tunnel face using the Tunnel Seismic Prediction method (TSP) – Lesson learned from the Pahang-Selangor raw water transfer tunnel, Malaysia

In this study, Tunnel Seismic Prediction method (TSP) was used to predict the geological condition ahead of the tunnel face. The tunnel which extends 44.6 km is intersected by several major faults and few lineaments. The ability of the TSP system was investigated to predict one the anticipated fault which had been inferred from the geological map. Then, the TSP results were applied to delineate the relation between seismic velocities and geological parameters for the predicted fault ahead of the tunnel face. The results show a velocities drop 10 to 40 m ahead of the tunnel face which had indicated the initial findings of the unfavorable geological condition from geological map. From the verification analyses, the TSP results are substantially correlated with the Tunnel Boring Machine (TBM) driving data, geological mapping, rock class grade point and uniaxial compressive strength obtained using Rock Schmidt Hammer. In this case, the TSP was a helpful tool for the tunnel contractor in predicting zones of geological instabilities during the excavation process of long deep tunnel. Thus, such prediction method can be used as a decision support in the observational design and construction system especially in determining suitable tunnel support system in the expected unfavourable geological conditions.