The influence of tunnel excavation on the overlying pipeline cannot be ignored when the distance between the pipeline and tunnel is minor. For the special condition of tunnel excavation through the existing pipeline, the transparent soil and PIV technologies were adopted to conduct a comparative study on the deformation regularities of continuous and non-continuous pipelines. The dynamic change of soil displacement with tunnel excavation was monitored, and the influence of bending stiffness, depth and section length of pipelines on their deformation was analyzed by the control variable method. The results show that: The settlement patterns of both continuous and non-continuous pipelines are basically consistent with the Gaussian settlement curve. The maximum settlement value of continuous pipeline decreases with the increase of flexural stiffness and increases with the increase of pipeline burial depth. The maximum settlement value of discontinuous pipeline increases first and then decreases with the increase of pipeline section length. In addition, the relative position between the non-continuous pipeline and tunnel has a significant impact on the pipeline settlement. When the non-continuous pipeline interface is directly above the tunnel axis, its maximum settlement value is significantly higher than those value when the tunnel axis is directly below the pipeline joint center, indicating that the tunnel crossing position close to the non-continuous pipeline interface is the most dangerous situation which should be avoided as soon as possible in design.

Considering the engineering characteristics of shallow buried tunnels in loess area and probable large deformation of soil, the overlying pipe was divided into pipe-soil detached area and pipe-soil deformation coordination area during excavation process, and a calculation model considering pipe-soil detachment interaction was proposed. On the basis of considering the influence of pipe buried depth on subgrade reaction modulus, the modified semi-infinite Pasternak elastic foundation beam model was used to consider soil continuity. After applying free-soil displacement load to pipe by two-stage method, the mechanical models and governing differential equations of both the detached area and coordination area were established, and the theoretical solution was given. Then, through comparison with the existing model test data, the proposed method in this paper was verified to be accurate, and the solution of pipe deformation without considering detachment was conservative. Finally, the main influencing factors of pipe deformation were compared and analyzed. Results show that, the maximum deformation of pipe increases with the increase of soil loss, and decreases with the increase of pipe-tunnel spacing, pipe stiffness and soil strength, but the magnitude of decreases are slowed down with the increase of each parameter. The range of detached area increases with increase of pipe stiffness, soil elastic modulus and pipe-tunnel spacing, while the maximum deformation difference which represents the degree of pipe-soil detachment increases with the increase of pipe stiffness, but contradicts with soil elastic modulus and pipe-tunnel spacing.