Abstract: The frequent occurrence of buried pipeline accidents caused by the ground collapse and subsidence makes it urgent to carry out experimental studies on the mechanical response under different subsidence effects. A systematical survey of the pipeline strain, earth pressure and soil deformation was conducted considering the effects of ground subsidence and collapse. The result showed that due to the arching effect at the top of the pipeline, the strain and earth pressure firstly increased and then decreased with the extension of the collapse zone, while they increased as the subsidence zone extended during the collapse and settlement. In the subsidence and collapse zones, the pipeline along the axial direction exhibited a saddle shape with both ends convex and concave in the middle. Pipeline deformation was more significantly affected by the subsidence. When the subsidence and collapse were both 50 mm, the maximum strain at the top, bottom and middle of the pipeline increased by approximately 18.8%, 249% and 273% compared to the ground collapse, respectively. It could be seen by comparing the ratio of the increasing area to the decreasing area of earth pressure around the pipeline λ that λ in the subsidence was increased by 78% compared with that in the collapse; therefore, the pipeline was subjected to larger earth pressure during the subsidence. Based on the modified Marston calculation model, a method for predicting the vertical earth pressure during ground subsidence was proposed, and the accuracy of the method was verified using the model test results.

Key words: pipeline, ground subsidence, soil collapse, pipeline strain, earth pressure around the pipeline