ABSTRACT
Underground excavation has evolved with better understanding of rock mechanics, yet many historical tunnels remain products of trial-and-error approaches. Restoration of such tunnels poses major challenges due to limited documentation. This paper presents a case study of a wartime tunnel located in the Philippines, highlighting how modern geophysical and geodetic technologies were used to generate a digital ground model with the mapped tunnel surface along with the overlying structures. Engineering geological mapping provided critical details on rock discontinuities, informing preliminary designs based on rock mass quality indices. Geotechnical modeling confirmed that most tunnel sections only required spot bolting, though some areas needed reinforced shotcrete lining to manage water ingress. Portal stabilization requires rock bolts or soil nails and portal canopies for aesthetic enhancement. From historic, geologic, geotechnical, up to architectural considerations, this work showcased the distinct roles of various scientific fields to address complex issues in preserving our heritage.
