Numerical simulation of mechanical response of buried pipelines under different settlement modes

Objective The rapid expansion of oil and gas pipeline construction in China, coupled with accelerating urbanization, has heightened safety concerns from stratum soil settlement, posing significant risks to buried pipeline operations. Stratum soil settlement is a time-dependent process; although similar settlement outcomes may arise from varying development patterns, current safety evaluations overlook how these differing settlement processes affect the mechanical response of buried pipelines.

Methods Finite element numerical simulation was employed. By varying settlement counts and sequences across different areas, simulations of buried pipeline settlement under various modes were conducted and validated experimentally. The simulation results enabled a quantitative comparison and analysis of the mechanical responses of buried pipelines under different settlement modes.

Results Under reverse-order step-by-step settlement, the maximum surface settlement above the pipeline exceeded that of the one-time overall settlement mode. Although soil separation beneath the pipeline center was severe, the pipeline’s mechanical response remained lower than in the one-time overall settlement. When settlement counts were equal, differences in pipeline mechanical response due to settlement sequence exceeded 50％, highlighting the significant impact of settlement processes. For the same settlement amount, the one-time overall mode caused more than twice the maximum displacement and longitudinal tensile strain compared to multi-step settlement. Consequently, one-time overall settlement induced a more intense mechanical response, increasing the risk of damage to buried steel pipelines.

Conclusion Large-scale local stratum soil settlement has limited impact on the overall mechanical response of buried pipelines. A comprehensive analysis of the settlement development across the entire area is necessary. To minimize pipeline mechanical response for a given settlement range and amount, it is recommended to first analyze large-scale settlement in the center of the area, followed by multiple smaller settlements toward the boundaries. These findings are crucial for accurately assessing the safety of buried pipelines under stratum soil settlement.