Abstract
Winkler elastic foundation beam theory is often used to observe the influence of underground engineering construction on pipelines. Excavation under existing pipelines disturbs the lower strata to varying extent, which creates significant differences in the subgrade coefficients. Ignoring these differences can severely impact the accuracy of calculation results. A theoretical model of the effects of underground excavation on upper-level existing pipelines was developed in this study based on Winkler elastic foundation beam theory and considering the difference of subgrade coefficients under the existing pipeline. Methods for determining the subgrade coefficient under the influence of construction disturbance and other relevant parameters are proposed. The theoretical model can be used to calculate the settlement of an existing pipeline under the influence of underground excavation. The calculated settlement was compared with settlement measurements to find that the subgrade coefficient of the excavation section is the most important parameter in the calculation process. The suitable value range of the excavation subgrade coefficient is relatively large, as it has a relatively minor influence on the calculation result. When the value of subgrade coefficient of each section is appropriate, the calculated settlement curve is in close accordance with the measured settlement curve.
Highlights
Theoretical Calculation ModelUnderground pipelines are laid along a roadway. Most underground tunnels cross the road vertically and intersect with the existing pipelines vertically. e impact of the underground excavation project intersecting with the existing pipeline vertically is under investigation here (Figure 1)
Advances in Civil Engineering accumulated experiences in parameter values, and is most widely used in engineering. e two-parameter elastic foundation beam is more comprehensive in theory but includes less experience in the parameter value selection process; whether the parameter value is appropriate is directly related to the accuracy of calculation results. e Winkler elastic foundation beam theory was utilized in the present study to develop a calculation model of the influence of excavation on the upper-level pipeline
E stratum under an existing upper-level pipeline is disturbed as an excavation project passes under it. e disturbance is most intense above the excavation section though there is disturbance in a certain area near the excavation area. e mechanical properties of the soils in these two areas change significantly at this point compared with the original stratum, so there is a substantial difference in the subgrade coefficient
Summary
Underground pipelines are laid along a roadway. Most underground tunnels cross the road vertically and intersect with the existing pipelines vertically. e impact of the underground excavation project intersecting with the existing pipeline vertically is under investigation here (Figure 1). Where EI is the bending stiffness of the existing pipeline, N∙m2; ωi is the deflection of each section of the existing pipeline, m, i 1, 2, 3; x is the distance between each point in the right half of the existing pipeline and point O, m; ki is the subgrade coefficient of each section under the existing pipeline, N/m3, i 1, 2, 3; qi is the Earth pressure borne by each section of the existing pipeline, Pa, i 1, 2, 3; and b is the calculated width of the foundation reaction, m. E analytical solutions of the undetermined coefficients Ai, Bi, Ci, and Di were obtained here in MATLAB and substituted into formulas (5)–(8) to obtain the deflection, rotation angle, bending moment, and shear force generated at each point in the existing pipeline AE during excavation of the BC section. A system of 12 equations and 12 unknowns can be established by substituting formulas (5)–(8) into formula (3). e analytical solutions of the undetermined coefficients Ai, Bi, Ci, and Di were obtained here in MATLAB and substituted into formulas (5)–(8) to obtain the deflection, rotation angle, bending moment, and shear force generated at each point in the existing pipeline AE during excavation of the BC section. e safety of the existing pipeline can be evaluated based on the results by selecting appropriate judgment standards
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
