Seismic performance assessment of underground utility tunnel and internal pipeline considering effects of tunnel joints

Abstract

Underground utility tunnel is a passage built underground to carry utility pipelines such as electricity, steam, water, and sewer pipelines. To ensure the quality and efficiency of the construction, circumferential joints are always installed between two adjacent tunnel segments to prevent damage caused by shrinkage and creep of mass concrete in construction, and uneven settlement during daily operation. However, the lack of verification and quantification of the seismic performance of utility tunnel and internal pipeline system considering the effects of joints remains a critical deficiency of the design of utility tunnels in seismic intensive regions. This study aims to investigate the response of long-extended underground utility tunnel and internal pipeline system subjected to non-uniform earthquake ground motions. The utility tunnel and internal pipeline system are modeled as a double-beam system on foundation using OpenSees software. Soil-structure interaction, joint connections and internal pipeline pedestals are modeled as springs with different mechanical properties. A typical response-spectrum compatible bedrock ground motion (including two directions) is collectively amplified into different intensity levels. One-dimensional dynamic site response analysis and wave passage effect are conducted before dynamic analyses of the utility tunnel and internal pipeline system. The numerical results indicate that the utility tunnel joints can help to mitigate the seismic damage of utility tunnel, while enlarge the seismic response of internal pipeline. For the case of 0.20 g intensity level, the axial force, shear force, and bending moment of the utility tunnel with joints are 41.15%, 54.92%, and 78.09% less than those without joints, respectively; the internal pipeline in utility tunnel with joints exhibits significant increases of 21.67%, 1667.24%, and 40.02% in axial force, shear force, and bending moment compared to those without joints. The increasing rates of utility tunnel and internal pipeline responses diminish as seismic intensity levels rise, indicating a progressive plastic deformation within the structures.