Abstract
Taiwan is located at the intersection of the Eurasia and Philippine plates, where earthquakes frequently occur. Maintenance of underground infrastructure, such as buried pipelines, is an important municipal issue in daily life. The Taipei Water Department plans to construct multiple large-diameter water mains using the shield tunneling method underneath floodplains or rivers to enhance the performance of water pipeline facilities. The plan involves laying underground pipes after completing the tunnel and filling the annular gap between the pipeline and the concrete segments with backfill, such as cementitious material or controlled low-strength material (CLSM), to secure the pipeline. U-shaped ductile cast iron pipes are used as the main type of pipeline. This study aims to recommend a quantity of poured cementitious material (full and half-filled) for this kind of pipeline facility and consider three different compressive strength levels (10, 40, and 140 kgf/cm²). Numerical analysis was conducted using ABAQUS to analyze the effects of different poured amounts and compressive strengths of cementitious materials on the U-shaped pipe joints under pseudo-static conditions. Comparisons of the variations in elongation and rotational angles have been made among the cases. The study reveals that ductile cast iron pipes exhibit larger rotational angles and elongations under full-filled conditions than under half-filled conditions. The compressive strength of the cementitious-filled material has a negligible impact on the rotational angles and elongations of the pipeline. The simulations show that half-filled cementing material with lower compressive strength can provide the required support to secure the pipeline, representing the most cost-effective plan. As a result, this study can serve as a valuable reference for future engineering design and planning, contributing to reducing pipeline disasters and enhancing economic benefits.
