ABSTRACT
This paper explores the design and construction challenges of a 27m span cavern beneath an urban area containing high-rise buildings and deep basements. Support types were designed to suit a potential range of ground conditions to be confirmed during construction. Numerical analyses assessed the stability of narrow rock pillars (width-to-height ratio <1), tunneling-induced settlement under buildings, and impacts of future developments on the tunnel. Innovative solutions were implemented for each challenge. Potential pillar conditions were classified into four categories, with tailored treatments designed using 3D finite difference analysis (FLAC3D), 2D finite element analysis (RS2), and 2D distinct element modeling (UDEC).
