An Investigation of Effects and Safety of Pipelines due to Twin Tunneling

Abstract

To efficiently and accurately predict the effects of twin tunneling on adjacent buried pipelines, the effects of upward and downward relative pipeline-soil interactions were considered. A series of numerical parametric studies encompassing 8640 conditions were performed to investigate the responses of a pipeline to twin tunneling. Based on the dimensionless analysis and normalized calculation results, the concept of equivalent relative pipeline-soil stiffness was proposed. Additionally, expressions for the relative pipeline-soil stiffness and relative pipeline curvature and for the relative pipeline-soil stiffness and relative pipeline settlement were established, along with the related calculation plots. Relying on a comparison of prediction results, centrifuge model test results, and field measured results, the accuracy and reliability of the obtained expressions for predicting the bending strain and settlement of adjacent buried pipelines caused by twin tunneling were validated. Based on the calculation method, the maximum bending strain and maximum settlement of pipelines can be calculated precisely when the pipeline parameters, burial depth, soil parameters, and curve parameters of ground settlement due to tunneling are provided. The proposed expressions can be used not only to predict the maximum bending strain and maximum settlement of pipelines caused by single and twin tunneling but also to evaluate the effects of single and twin tunneling on the safety of existing buried pipelines. The relevant conclusions of this article can also provide a theoretical basis for the normal service of buried pipelines adjacent to subway tunnels.

Analysis of the Buried Pipeline Response Induced by Twin Tunneling Using the Generalized Hermite Spectral Method

“…To prove the convergence of the proposed solution, the effects of the scaling factor β and the truncated series number N are first illustrated and discussed. For twin tunnel excavations, the induced greenfield displacement can be evaluated according to Equation (3), and for determining the buried pipeline response, Equation (3) should be expanded as Equation (22) with Hermite functions. The approximation performance of Equation ( 22) is the fundamental premise to obtain a reliable result for the pipeline response.…”

“…The approximation performance of Equation ( 22) is the fundamental premise to obtain a reliable result for the pipeline response. Without loss of generality, herein, the overall relative error at all the collocation points is adopted to assess the approximation performance of Equation (22). For five given scaling factors β (i.e., β = 6, 8, 10, 12, 14), Figure 2a shows the overall relative error from Equation (22) with the increasing truncated series.…”

“…Without loss of generality, herein, the overall relative error at all the collocation points is adopted to assess the approximation performance of Equation (22). For five given scaling factors β (i.e., β = 6, 8, 10, 12, 14), Figure 2a shows the overall relative error from Equation (22) with the increasing truncated series. It can be seen that for all the scenarios with different scaling factors, the overall relative error decreases rapidly with the increase in the adopted truncated series.…”

“…For the scenario of β = 6, the overall relative error decreases to below 5% when the adopted truncated series exceeds 20, while for the other cases, just 10 truncated series are needed to reduce the overall relative error below 5%. Similarly, taking the truncated series as 10, 20, 30 and 40 in turn, Figure 2b illustrates the overall relative error from Equation (22) with the increase of the scaling factor. As observed, with the increase in the scaling factor, the overall relative error initially decreases to a minimum value and then gradually increases.…”

“…Ma et al [20,21] developed a series of centrifuge tests to study the influences of tunnel depth, soil loss ratio, and excavation sequence on the buried pipeline response. Yu et al [22] performed a comprehensive numerical simulation encompassing 8640 conditions to investigate the mechanical and deformation behavior of buried pipeline that was adjacent to undercrossing twin tunnels. Compared with physical model experiments and numerical simulations, theoretical solutions are commonly more convenient and can provide guidance more efficiently for the primary designs of actual projects [3,19,23].…”