Abstract: In highly developed urban cores, constructing underground garage link roads can help alleviate ground-level traffic pressure and enhance the pedestrian and cycling environments. To resolve spatial constraints encountered in conventional construction approaches within severely restricted urban branch roads (12-m red-line width) and minimal building setbacks, the authors present a design approach for double-deck underground garage link roads: (1) For building cross-sections, side-exhaust and top-exhaust ventilation ducts are proposed. The clear height of link roads is larger than site garages, side-exhaust configurations are recommended, requiring dedicated ventilation and smoke extraction measures at site access points. (2) The traffic organization between double- and single-deck underground garage link roads is comparatively analyzed, and two optimized traffic organization—a through-type configuration and a semi-loop configuration—are presented, ensuring seamless integration between the garage link roads and urban underground arteries. (3) Due to the height difference between clear height of link roads and garage, three vertical connection methods (upper deck connection, lower deck connection, and middle transition) are proposed. The upper deck connection is recommended for maximizing development value. (4) Three construction modes (joint construction, temporary use enclosure, and temporary use partial enclosure) are proposed based on the development situation of different surrounding plots, to coordinate the construction of underground space and achieve resource intensive. The relevant research findings have been applied to the Shenzhen Bay Super Headquarters Base Underground Garage Link Road. The project is currently under construction, with part of the tunnel retaining structures already completed, demonstrating the rationality and feasibility of the design methods.

Key words: double-deck underground garage link road, cross-sectional configuration, traffic organization scheme, construction modality, retaining structure design