Response of pressurized municipal pipelines to tunneling

Tunneling beneath existing pressurized municipal pipelines is becoming increasingly common in urban construction, yet current preliminary evaluation methods often neglect the influence of internal pressure on pressurized pipeline response. To address this, an analytical method is proposed based on the classical Euler-Bernoulli beam on a Pasternak foundation model, which innovatively incorporates the coupled effects of tunneling-induced ground deformation and internal pressure-induced stress on the pressurized pipeline response. This method employs a modified Peck formula to predict soil settlement induced by single and twin tunnels excavation, establishes coupled pipeline-soil deformation equations, and introduces a composite stress evaluation method that incorporates both axial and circumferential stress induced by internal pressure. The proposed method is validated against two sets of field monitoring data, demonstrating good accuracy and engineering applicability. Parametric analyses are conducted using three types of gas pipelines with different internal pressure levels. Results show that ground settlement, soil elastic modulus, and internal pressure all significantly affect pressurized pipeline responses and exhibit a clear synergistic amplification effect. Error analysis further reveals that neglecting internal pressure leads to significant underestimation of pressurized pipeline responses induced by tunneling, highlighting the necessity of incorporating internal pressure effects in stress evaluation. For high-pressure pipelines (>1.6 MPa), the maximum errors in settlement and stress can reach 47.5% and 62.1%, respectively, indicating that internal pressure must be fully considered in both displacement and stress analyses. In contrast, for medium-pressure and low-pressure pipelines (≤0.4 MPa), the settlement error remains below 1%, and internal pressure needs to be included only in stress evaluation. Additionally, ground improvement and reduction of operating pressure are effective measures to mitigate the structural response of high-pressure pipeline to tunneling. This method provides a rapid and practical tool for preliminary evaluation of pressurized pipeline responses to tunneling and offers theoretical support for risk control and protection strategies.