Abstract:Excavation of subway tunnels often causes additional deformation or even damage of adjacent underground pipelines. The jointed pipeline can be regarded as a beam on elastic foundation. According to the performance of pipeline joints transferring bending moment, the joints were simplified as “free hinge” and “spring hinge”. Based on Winkler’s foundation model, a governing differential equation for the pipeline deformation was given and solved by transfer matrix method. The field matrix for pipeline sections and the point matrix for pipeline joints were derived, and the linear equations about unknown boundary values of the differential equation were obtained. Comparing calculation results of this paper with finite element method, empirical method and measured data, the correctness of the transfer matrix method was verified. Parametric analysis of factors influencing pipeline deformation was carried out. Results show that, the worst situation for joint deformation is when tunnel centerline is right below the joint. The relative rotation angle of free hinge is hardly affected by foundation coefficient in the soil stratum. Therefore, the pipeline with free hinge is easy to have a large relative rotation angle. The peak value of the relative rotation angle appears when the length of the pipeline segment is 1.6i. The limit of the relative rotation angle is 1.1Smax/i. This limit can be used as a conservative estimate of the relative rotation angle in the case of shortage of design data.