Abstract: In order to investigate the Soil-pipe interaction during tunnelling, Lab model tests were carried out in Yangtze River sand filled in a custom-made model box,during which the model continuous pipeline(HDPE) was buried.The results show that the behavior of pipeline is negative downdrag in the middle but is positive dowdrag at both ends; the influence zone extended 3D adjacent to the pipeline in sand; the ratio of pipeline to soil deformation curvature,bending moment and strains of pipeline decrease with the increasing of ground loss; the value of additional load on the pipeline increase and the earth pressure under pipeline reduce to zero in the middle, while with the increase of ground loss, the gap width grows bigger to be a constant; mechanisms of Soil-pipe interaction are discussed, and it is determined that major factors are width coefficient,largest settlement and the ratio of buried depth to diameter of pipeline etc, and a computing formula is put forward for the relative pipe-soil bending rigidity based on the tested results.

Key words: tunnelling, Soil-pipe interaction, Lab model test, pipeline, sand