Abstract: Microutility tunnels are always limited in space, leak, and difficult to maintain. To promote such tunnels in old urban areas, innovative solutions are proposed, including the installation of mortise and tenon joints and the application of a rubber membrane between the covers of a microutility tunnel to resolve water infiltration issues, the design of drainage and cable outlet cavities at the bottom of the tunnel to avoid water accumulation, the development of a lie-flat maintenance system with guide rails and upgradable sliding maintenance beds to address maintenance difficulties caused by the confined space within the tunnel, and the implementation of concrete lining walls and the elimination of expansion slots in foundation pits to minimize the space occupied by microutility tunnel construction. Herein, a case study is conducted on the municipal infrastructure upgrade project in the historic and cultural district of Duobao road. The overall concept, technical approach, and implementation method for the design of microutility tunnels in two streets are presented. The research results demonstrate that incorporating drainage and cable outlet cavities at the bottom of microutility tunnels facilitates a more compact layout of pipelines, ensures no water accumulation in the tunnels, and avoids the maintenance difficulties that arise from cable outlets positioned at the top of microutility tunnels. The combination of micropiled foundation, internal braces, and lining walls can meet the requirements of limited construction sites and minimally impact the safety of existing structures on both sides.

Key words: microutility tunnel, old urban area, directly buried pipeline