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Model Tests on Underpassing of Different Underground Discontinuous Pipelines by a Shield in Loess
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    Abstract:

    Aiming at the problem of pipeline settlement and stress caused by urban shield tunnel construction underneath an existing gas pipeline, indoor model tests and finite element numerical simulations are carried out with an under-construction highway in Henan Province as the engineering background. Considering the effects of different discontinuous pipe joint spacing, joint stiffness and pipe-tunnel spacing, the effects of tunnel excavation on settlement, bending moment and pipe-soil contact stresses of discontinuous pipes under pipe-tunnel orthogonal conditions are investigated. The research results show that: a settlement concentration zone exists in loess shield orthogonal down through the pipeline, and in the range of the zone, the size of the pipeline joints and pipe section relative stiffness ratio of the pipeline average settlement growth rate has a greater impact on the pipeline average settlement growth rate, where the relative stiffness ratio is decreased from 1.30 to 0.21, and the average settlement growth rate of the discontinuous pipeline is increased by 1.5 times; relative stiffness ratio of the relative size of the discontinuous pipeline settlement and the bending moment played a decisive role; by defining the integrated stiffness ratio of the discontinuous pipeline, it reveals the maximum settlement change rule of the discontinuous pipeline and the relative change rule of the maximum positive and negative bending moments of the pipeline under different integrated stiffness ratios, in which the integrated stiffness ratio and the maximum settlement of the pipeline obey the 3rd polynomial fitting function, and the maximum positive bending moment of the pipeline obeys the 4th polynomial fitting function along with the change in the maximum negative bending moment value; the changes in the pipe-soil contact stresses of the pipeline are presented with a “bimodal type”. Numerical simulation shows that the maximum settlement of the pipeline decreases with the increase of the spacing between the tubes and tunnels, the turning point occurs at the ratio of the spacing between the tubes and tunnels and at the diameter of the tunnel excavation of one.

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  • Online: April 02,2024
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