Publication: Geological prediction ahead of tunnel face in limestone formation
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Date
2020-05-01
Authors
Zaki, Nur Farihan Mohammad
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Abstract
Construction tunnels are perceived as relevant development models used for road and rail transport systems, canals and utility transmissions, such as power supply, telecommunications and water. This study examines the construction of tunnels for the flood mitigation system implemented as part of the Timah Tasoh Western Flood Bypass project in Perlis. Tunnel construction works are classified as high-risk areas and are particularly challenging especially when they are constructed in limestone areas prone to failure due to unprecedented rock properties, such as cavity formation, cracks, weathering, water flow and discontinuities. To identify the geological conditions, long-, medium- and short-range geological predictions are performed ahead of the tunnel face by using horizontal seismic profiling (HSP), ground penetration radar (GPR) and advanced drilling, respectively. The actual geological conditions of karst limestones are determined via tunnel face mapping, which determines rock mass quality by using rock classification and Q-value systems. A comprehensive analysis is also performed to determine the accuracy of predictive methods that use tunnel face mapping in determining rock geological conditions. By referring to the actual geological conditions of the site, the tunnel face mapping analysis reveals that HSP, GPR and advance drilling have 15%, 30% and 88% differences in predicting geological conditions, respectively.