Centrifuge modeling of the influence of joint stiffness on pipeline response to underneath tunnel excavation

Any tunnel construction inevitably causes differential soil movements, resulting in additional adverse effects on existing pipelines. Although there are many jointed pipelines in practice, previous studies commonly simplified existing pipelines as continuous structures. In this study, centrifuge tests were designed and conducted to investigate the influence of joint stiffness on pipeline response due to tunnel excavation. Along the longitudinal pipeline direction, upward and downward pipe-soil relative movements were identified. Because of relatively flexible joints causing a reduction in the pipeline flexural stiffness, tunneling-induced maximum settlement in the jointed pipeline was much larger than that in the continuous pipeline. Tunnel excavation caused bending moment in the continuous pipeline only, while bending moment and joint rotation occurred simultaneously in the jointed pipeline. As a result of joint rotation, tunneling-induced maximum bending strain in the jointed pipeline was less than 42.4% of that in the continuous pipeline. If a jointed pipeline is assumed as a continuous structure, tunneling-induced pipeline settlement is underestimated, while bending strain is grossly overestimated. All the centrifuge test results were adopted to verify the validity of calculation charts for estimating tunneling-induced maximum bending strain and joint rotation in existing pipelines.