Numerical Analyses of the Stress and Ultimate Bearing Capacity for Small-Diameter Gas Pipelines under Multiple-Wheel Heavy Vehicle

Vehicle load is the most frequent live load on cross-highway pipelines. Cross-highway pipelines will bear great stress under the rolling action of heavy vehicles, which leads to pipeline failure and damage. However, the current vehicle–road model and the pipeline–soil model are calculated independently of each other, which cannot accurately solve the stress response of buried pipelines in the process of a vehicle rolling in real time. This paper solves this problem. To study the real-time influence of vehicle load, vehicle speed, rolling position, and other dynamic factors on pipelines’ stress, the ultimate bearing capacity of small-diameter gas pipelines under the action of a heavy vehicle rolling was quantified. This paper established the vehicle–pavement–pipeline model by combining Adams version 2020 and Abaqus version 2020, and the pipeline’s dynamic stress response and ultimate bearing capacity under vehicle load were simulated numerically. According to the actual working conditions on-site, an experimental system for buried pipelines was established, and the test was verified with a 7-m-long pipeline. Simulated and experimental results were compared, and showed good agreement. The research results show that the stress on the pipeline is positively related to the vehicle load and diameter. However, with the increase in vehicle speed, the stress on the pipeline tends to decrease. When the burial depth of the pipeline reaches 1.5 m, the protective effect of soil on the pipeline is weakened. The study also found that the internal pressure has a certain protective effect which can reduce the impact of vehicle load on stress increment. This is a new discovery: the closer the rolling position is to the centerline of the pipeline, the greater is the peak stress. Finally, an evaluation method of the ultimate bearing capacity of buried pipelines and the overload warning index is proposed based on the von Mises stress, and vehicle overload warning curves were established. The vehicle overload warning curves can be used to determine whether the current vehicle load will be harmful to the pipeline, or to design the maximum vehicle load of a section in preliminary work. On-site application showed that the vehicle overload warning curves have high accuracy and can provide some guidance for the safe operation of the pipeline.