Vertical deflection of the existing pipeline due to shield tunnelling

Abstract:

Shield tunnelling will inevitably lead to the vertical deflection of existing pipelines. Based on a Pasternak-type two-parameter elastic foundation model，a two-stage analytical method for estimating the vertical deflection of existing pipelines is presented in this paper. With respect to the first stage, the Loganathan and Poulos analytical solution is used to estimate the free-soil settlement caused by shield tunnelling at the existing pipeline's position; in the second stage, the free-soil settlement is imposed to the existing pipeline, which is simplified as an infinite beam on a Pasternak foundation. The governing differential equations of the pipe are formulated and analytically solved, and the deflection and internal forces of the pipeline are obtained. The effects of the lateral soil beside the pipe are considered and more reasonable results are obtained. Foundation model parameters are determined by the simplifying elastic continuum method. The superiority of the Pasternak foundation model, compared to Winkler foundation model, is qualified by comparing results with numerical results. The accuracy of the proposed method is verified by a good agreement with the engineering case study.