Load Capacity of Perforated Reinforced Concrete Sewer Pipes

In cities, reinforced concrete pipes are often employed to construct storm sewer systems. Due to impervious base layers, stormwater runoff dominates rather than rainwater infiltration, leading to problems in aquatic ecosystems (e.g., degradation in urban watersheds, flood attenuation, and water quality). A thermoplastic perforated pipe can provide drainage channels in applications of solid waste landfills, mining heap leach pads, or irrigation systems. Inspired by these applications, perforation can be implemented in a reinforced concrete sewer to alter the moisture conditions in the ground under impervious base layers. Three-edge bearing tests and four-point flexural tests are conducted to investigate the structural integrity of perforated sewer pipes. A numerical model is also calibrated for use to optimize the layout design of drainage holes. It is found that perforation can result in strength degradation in concrete pipe, but the reduction in strength is not significant. A correlation between the ultimate load and opening ratio is established for the two testing conditions. The allowable opening ratio is determined as 0.2%, below which a perforated sewer can fulfill the requirements for both drainage and load resistance.